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 Table of Contents  
ORIGINAL ARTICLE
Year : 2014  |  Volume : 27  |  Issue : 4  |  Page : 801-808

Histological study on the possible protective effect of pentoxifylline on pancreatic acini of l-arginine-induced acute pancreatitis in adult male albino rats


Department of Histology, Faculty of Medicine, Menoufiya University, Menoufiya, Egypt

Date of Submission10-Oct-2014
Date of Acceptance09-Dec-2014
Date of Web Publication22-Jan-2015

Correspondence Address:
Walaa Abdellah Ismail Ibrahim Esa
Masged Elkhedr, Elbagour, Menoufiya
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/1110-2098.149789

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  Abstract 

Objective
The aim of this study was to determine the histological changes of l-arginine-induced acute pancreatitis and the possible protective effect of pentoxifylline on pancreatic acini in adult male albino rats.
Background
Acute pancreatitis is a reversible inflammation that is either localized to the pancreas or may spread to adjoining tissues.
Materials and methods
Forty adult male albino rats weighing 180-200 g each were used in this study. The rats were divided into four equal groups (10 rats each). Group I was the control group. In group II (l-arginine-treated), rats were administered two intraperitoneal injections of l-arginine at a dose of 200 mg/100 g/body weight with 1-h interval. They were randomly subdivided into two equal subgroups: in IIA, rats were killed after 24 h of the last l-arginine injection and in IIB, rats were killed after 1 week of the last l-arginine injection. In group III (l-arginine and pentoxifylline-treated), rats were administered l-arginine and pentoxifylline. l-arginine was given similar to group II and pentoxifylline was given as a single intraperitoneal injection at a dose of 12 mg/kg body weight/day. They were randomly subdivided into two equal subgroups: in IIIA, rats were given a single dose of pentoxifylline then were killed after 24 h and in subgroup IIIB, rats were given pentoxifylline daily for 1 week then were killed. In group IV (pentoxifylline-treated), rats were administered pentoxifylline as a single intraperitoneal injection of 12 mg/kg body weight/day for 1 week then rats were killed.
Results
l-arginine-treated rats for 24 h showed pancreatic edema, degenerative changes of pancreatic acini, and inflammatory cell infiltration. These changes were marked after 1 week; however, pentoxifylline supplementation in group III showed amelioration of the histological picture, which was marked after daily pentoxifylline treatment for a week.
Conclusion
It is concluded that pentoxifylline was found to improve the histological changes of pancreatic acini caused by l-arginine.

Keywords: Acute pancreatitis, l-arginine, pentoxifylline


How to cite this article:
Soliman ME, Kefafy MA, Mansour MA, Ali AF, Ibrahim Esa WA. Histological study on the possible protective effect of pentoxifylline on pancreatic acini of l-arginine-induced acute pancreatitis in adult male albino rats. Menoufia Med J 2014;27:801-8

How to cite this URL:
Soliman ME, Kefafy MA, Mansour MA, Ali AF, Ibrahim Esa WA. Histological study on the possible protective effect of pentoxifylline on pancreatic acini of l-arginine-induced acute pancreatitis in adult male albino rats. Menoufia Med J [serial online] 2014 [cited 2020 Mar 29];27:801-8. Available from: http://www.mmj.eg.net/text.asp?2014/27/4/801/149789


  Introduction Top


Acute pancreatitis (AP) is a reversible inflammation that is either localized to the pancreas or may spread to adjoining tissues. It is characterized by tissue edema, acinar necrosis, hemorrhage, fat necrosis, and perivascular infiltration of inflammatory cells in the pancreas [1]. It is associated with substantial morbidity and mortality ranging from 15 to 40% in its severe form [2].

The prognosis for AP depends largely upon the degree of pancreatic necrosis and the intensity of multisystem organ failure generated by the systemic inflammatory response. Growing evidences have shown that cytokines synthesized and released by activated leukocytes could propagate and amplify both pancreatic damage and systemic inflammatory response in AP. However, the mechanism for migration and activation of leukocytes in inflamed pancreas remains largely uncharacterized [3].

l-arginine is an amino acid that is necessary for the body to make proteins. It is used for improving wound healing and shortening recovery time after surgery [4]. It was previously proved by many authors to induce pancreatitis in experimental animals both biochemically and histologically [5],[6].

Pentoxifylline is xanthine derivative that leads to broad-spectrum effects against cell proliferation and inflammation. It is an inhibitor of production of interleukin-1 and interleukin-6, an inhibitor of T-cell and B-cell activation, and a suppressor of neutrophil degranulation, thus reducing inflammation and innate immunity [7]. Several studies have revealed that pentoxifylline is an active inhibitor of tumor necrosis factor-a (TNF-a). Therefore, it could be considered as a therapeutic option in TNF-a-mediated diseases [8]. Therefore, this work was carried out to study the histological changes induced by l-arginine in pancreatic acini and to clarify the possible protective effect of pentoxifylline on these changes.


  Materials and methods Top


Materials

Animals

Forty adult male albino rats weighing 180-200 g each were used in this study. They were kept at the same environmental condition with free access to food and water ad libitum.

Drugs

  1. l-arginine is available in the form of powder produced by Elgomhoria Company, Egypt, prepared as a solution in 0.9% saline to a final concentration of 400 mg/ml.
  2. Pentoxifylline is available in the form of powder produced by Aventis Company, prepared as a solution in distilled water to a final concentration of 2.4 mg/ml. It is given as a single intraperitoneal injection at a dose of 12 mg/kg body weight [9].


The rats were divided into four equal groups (10 rats each) as follows:

Group I (control): Rats were kept without any treatment. Rats were killed at the end of the experimental groups.

Group II (l-arginine-treated): Rats were administered two intraperitoneal injections of l-arginine at a dose of 200 mg/100 g/body weight with 1-h interval [10]. Thereafter, they were randomly subdivided into two equal subgroups:

IIA:

Rats were killed after 24 h of the last l-arginine injection.

IIB:

Rats were killed after 1 week of the last l-arginine injection.

Group III (l-arginine and pentoxifylline-treated): Rats were administered l-arginine and pentoxifylline; l-arginine was given similar to group II and pentoxifylline was given as a single intraperitoneal injection at a dose of 12 mg/kg body weight/day. They were randomly subdivided into two equal subgroups:

IIIA: Rats were killed after 24 h.

IIIB:

Rats were killed after 1 week of daily administration of pentoxifylline.

Group IV (pentoxifylline-treated): Rats were administered pentoxifylline; it was given as single intraperitoneal injection of 12 mg/kg body weight/day for 1 week then rats were killed.

Methods

At the end of each detected period, rats were killed by decapitation. Tissue samples were obtained, rapidly fixed in 3% glutaraldehyde for 3 h, and then processed for electron microscopic study [11]. Semithin sections were stained with toluidine blue. Other tissue samples were fixed in 10% formal saline and processed to make paraffin blocks. Paraffin sections of 5-6 μm thickness were stained with H&E for histological examination and Masson trichrome for detection of collagen [12].

Statistical analysis

The number of secretory granules of the control and treated groups was recorded in table. Thereafter, data were statistically analyzed using SPSS (Statistical Package for Social Sciences). Data were expressed as mean ± SE and analyzed using Student's t-test for comparison between two groups. Differences were regarded as nonsignificant if P value was greater than 0.05, significant if P value was less than 0.05, or highly significant if P value was less than 0.01 [13].


  Results Top


Light microscopic results

Control group (group I)

Sections of this group showed the normal architecture of pancreas; the gland was covered by connective tissue capsule that sends connective tissue septae dividing the gland into multiple lobes and lobules. The pancreatic lobules were of different sizes and shapes. They were formed of closely packed acini separated from each other by thin connective tissue septae [Figure 1]a. The acinar cells were pyramidal in shape with basal rounded vesicular nuclei and prominent nucleoli. The cytoplasm of acinar cells showed basal basophilia and apical acidophilia. Centroacinar cells with oval nucleus appeared in the center of some pancreatic acini [Figure 2]a.
Figure 1: (a) A photomicrograph of the pancreas of the control group showing connective tissue capsule (C) and trabeculae (T) dividing the gland into multiple lobules with different sizes and shapes separated by thin connective tissue septa (→) (H&E ×200). (b) A photomicrograph of pancreas of the control group showing the pancreatic acini lined with large pyramidal cells with basal rounded vesicular nuclei. Basal basophilia and apical acidophilia of acinar cells are observed. Notice the centroacinar cell (CA) that appears in the center of pancreatic acinus with oval nucleus (H&E ×1000). (c) A photomicrograph of pancreas of the control group showing very thin connective tissue capsule (C) and connective tissue septae (→) in-between pancreatic lobules (L) (Masson trichrome ×100). (d) A photomicrograph of a section of pancreas of the control group showing zymogen granules (ZG) (dark blue dots) in the apical part of the cells lining pancreatic acini (toluidine blue ×1000).

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Figure 2: (a) A photomicrograph of the pancreas of group IIA showing loss of normal lobular architecture. Some acinar cells show vacuolation (V) of their cytoplasm and pyknosis (P) of their nuclei. Notice edema and perivascular inflammatory infiltrate (→) (H&E ×400). (b) A photomicrograph of pancreas of group IIA showing edema, extravasation of blood (→), and cellular infiltrate (group I) among degenerated acini (H&E ×200). (d) A photomicrograph of pancreas of group IIA showing collagen fibers around blood vessels and around acini (→) (Masson trichrome ×100). (c) A photomicrograph of a section of pancreas of group IIA showing few apical zymogen granules (ZG) in some cells lining pancreatic acini and absence of these granules in other cells (→) (toluidine blue ×1000).

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Masson trichrome-stained sections showed very thin connective tissue capsule and connective tissue septae in-between pancreatic lobules [Figure 3]a. Toluidine blue-stained zymogen granules were seen in the apical part of pancreatic acinar cells [Figure 4]a.
Figure 3: (a) A photomicrograph of pancreas of group IIB showing massive distortion of the general architecture, necrosis of most of acinar cells (N). Other acini appear degenerated (D) with cytoplasmic vacuoles (V) and deeply stained pyknotic nuclei (P). Edema with inflammatory cellular infiltrate in the pancreatic interstitium are also observed (→) (H&E ×200). (b) A photomicrograph of pancreas of group IIB showing massive deposition of collagen fibers around blood vessels, in-between pancreatic acini and in the area of inflammatory reaction (→) (Masson trichrome ×100). (c) A photomicrograph of a section of pancreas of group IIB showing absence of the apical zymogen granules in most of acinar cells lining pancreatic acini (→), whereas other cells show few secretory zymogen granules (ZG) (toluidine blue ×1000).

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Figure 4: (a) A photomicrograph of pancreas of group IIIA showing nearly normal pancreatic lobulation. However, some acinar cells appear with vacuolated cytoplasm and pyknotic nuclei (→) (H&E ×400). (b) A photomicrograph of pancreas of group IIIA showing traces of collagen fibers around blood vessels and in-between pancreatic lobules compared with group IIA (→) (Masson trichrome ×100). (c) A photomicrograph of the pancreas of group IIIA showing the majority of acinar cells with excess secretory zymogen granules (ZG). However, few other cells show depletion of secretory zymogen granules (→) (toluidine blue ×1000).

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l-arginine-treated group (group II)

Subgroup IIA (rats killed 24 h after l-arginine injection):
Sections of this group showed variable degenerative changes of pancreatic acini with loss of normal lobular architecture; some acinar cells showed vacuolation with pyknosis of their nuclei and reduced basal basophilia [Figure 1]b. Edema, congestion, extravasation, and inflammatory cellular infiltration among the degenerated pancreatic acini and around the blood vessels were observed [Figure 2]b.

Deposition of few collagen fibers around blood vessels and in-between the degenerated pancreatic acini was observed [Figure 3]b. Toluidine blue-stained sections showed few deeply stained apical zymogen granules in some acini, whereas other acini showed absence of these granules [Figure 4]b.

Subgroup IIB (rats killed 1 week after l-arginine injection): Sections of this group showed massive destructive changes including massive distortion of the general lobular architecture and necrosis of most of acinar cells with excessive inflammatory cellular infiltrate, whereas other acinar cells showed vacuolation and pyknosis of their nuclei [Figure 1]c. Masson trichrome-stained sections revealed massive deposition of collagen fibers in the area of degenerated pancreatic acini and area of inflammatory infiltrate [Figure 2]c. Toluidine blue-stained sections showed marked depletion of secretory activity of pancreatic acinar cells as revealed by absence of apical zymogen granules in most of pancreatic acinar cells, whereas other acini showed few granules [Figure 3]c.

l-arginine and pentoxifylline-treated group (group III)

Subgroup IIIA (rats killed after 24 h):
Sections of this group showed mild improvement of the histological picture. The pancreatic lobular architecture appeared nearly normal. However, some acinar cells showed vacuolated cytoplasm and deeply stained pyknotic nuclei [Figure 1]d. Masson trichrome-stained sections revealed traces of collagen fibers around blood vessels and in-between pancreatic acini [Figure 2]d compared with group IIA. The majority of pancreatic acinar cells showed numerous apical zymogen granules. However, few acinar cells showed depletion of secretory granules in toluidine blue-stained sections [Figure 3]d.

Subgroup IIIB (rats killed after 1 week): Sections of this group showed good improvement of the histological picture. The pancreatic lobular architecture appeared nearly normal. However, some acinar cells showed deeply stained pyknotic nuclei, whereas the majority of acinar cells appeared with vesicular nuclei. The inflammatory reaction and the vascular congestion completely disappeared [Figure 1]e.

Masson trichrome-stained sections revealed traces of collagen fibers deposited around blood vessels and in-between pancreatic lobules nearly the same as control [Figure 2]e. The pancreatic acinar cells showed abundant zymogen granules in most of acinar cells nearly similar to that of control in toluidine blue-stained sections [Figure 3]e.

Pentoxifylline-treated group (group IV)

Sections of this group revealed normal histological picture of pancreas nearly the same as the control group [Figure 1]f. Traces of collagen fibers were seen around blood vessels and among pancreatic lobules similar to the control group [Figure 2]f. Toluidine blue-stained sections showed abundant zymogen granules in pancreatic acinar cells [Figure 3]f.

Electron microscopic results

Control group (group I)

Electron microscopic examination of ultrathin sections of the pancreas of the control group showed pancreatic acinar cells with basal rounded vesicular nuclei and prominent nucleoli. The acinar cells showed cisternae of rough endoplasmic reticulum (rER) packed in the cytoplasm with mitochondria in-between. Electron dense zymogen granules were apically located [Figure 1]g.

l-arginine-treated group (group II)

Subgroup IIA (rats killed 24 h after l-arginine injection):
Electron microscopic examination of ultrathin sections of this group showed pancreatic acini with wide lumen compared with the control group. Some acinar cells appeared degenerated with intended nuclei, dilated cisternae of rER, and few secretory zymogen granules [Figure 2]g.

Subgroup IIB (rats killed 1 week after l-arginine injection): Ultrathin sections of this group showed more destructive changes. Most of acinar cells appeared degenerated with intended nuclei, dilated cisternae of rER, swollen degenerated mitochondria, few secretory zymogen granules, and numerous vacuoles. Other cells appeared necrotic having small eccentric nucleus, numerous cytoplasmic vacuoles, and no secretory zymogen granules [Figure 3]g.

l-arginine and pentoxifylline-treated group (group III)

Subgroup IIIA (rats killed after 24 h):
The pancreatic acini of this group showed mild improvement as evidenced by appearance of normal pancreatic acinar cells. The nuclei of acinar cells appeared vesicular with normal rounded contour; the cytoplasm showed regularly arranged cisternae of rER, normal mitochondria, and variable-sized secretory zymogen granules. However, some acinar cells appeared with dilated rER and few secretory zymogen granules. Congested blood vessel was seen among pancreatic acini [Figure 4]g.

Subgroup IIIB (rats killed after 1 week): Ultrathin sections of this group showed good improvement. Most of the acinar cells appeared with euchromatic nuclei, regularly arranged cisternae of rER, and numerous secretory zymogen granules of variable sizes [Figure 5]g.
Figure 5: (a) A photomicrograph of pancreas of group IIIB showing nearly normal pancreatic architecture. The majority of acinar cells appear with vesicular nuclei, whereas some pancreatic acinar cells show cytoplasmic vacuole (V) and deeply stained pyknotic nuclei (→) (H&E ×400). (b) A photomicrograph of pancreas of group IIIB showing traces of collagen fibers between lobules, around acini and blood vessels nearly similar to the control group(→) (Masson trichrome ×100). (c) A photomicrograph of the pancreas of group IIIB showing abundant apical zymogen granules (ZG) in most of pancreatic acinar cells nearly the same as the control group (toluidine blue ×1000).

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Pentoxifylline-treated group (group IV)

Ultrathin sections of this group revealed normal electron microscopic picture of pancreatic acinar cells the same as the control group. The cell showed basal rounded vesicular nucleus, numerous packed cisternae of rER, and abundant secretory zymogen granules of variable sizes [Figure 6]g.
Figure 6: (a) A photomicrograph of the pancreas of group IV showing pancreatic acini more or less similar to the control group. Notice myoepithelial cells around acini (→) and centroacinar cell (CA) (H&E ×1000). (b) A photomicrograph of pancreas of group IV showing traces of connective tissue fibers in the stroma almost the same as the control group (→) (Masson trichrome ×100). (c) A photomicrograph of a section of pancreas of group IV showing abundant apical zymogen granules (ZG) in the cells lining pancreatic acini the same as the control group (toluidine blue ×1000).

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Statistical results

Secretory granules count

There is a significant increase in the number of secretory granules in acinar cells of l-arginine and pentoxifylline-treated group (group III).


  Discussion Top


AP can present as a wide clinical spectrum ranging from a mild, self-limiting localized disease to fatal widespread multiorgans failure with high mortality rates. It is characterized by acute inflammation and necrosis of pancreatic parenchyma, hemorrhage, and inflammatory infiltration [14].

l-arginine is used in many medical problems such as congestive heart failure, angina pectoris, erectile dysfunction, preventing inflammation of the digestive tract in premature infants, intermittent claudication, pre-eclampsia, improving athletic performance, sickle cell disease, and improving healing of diabetic foot ulcers [15],[16].

This work was carried out to study the histological changes of l-arginine-induced AP and to clarify the possible protective effect of pentoxifylline on pancreatic acini of adult male albino rats.

In this study, rats treated with l-arginine after 24 h revealed variable degenerative changes at both L/M and E/M levels with loss of normal lobular architecture, edema with inflammatory reaction, and vascular congestion. These changes became more aggravated after 1 week of l-arginine treatment as revealed by massive distortion of lobular architecture, necrosis of most acinar cells, inflammatory reaction, and congestion of the blood vessels. These changes were in agreement with previous researchers [17],[18],[19],[20],[21] who reported that the histopathological picture of AP became predominant after 1 day of induction of AP and became more severe after 7 days.

The histological findings of pancreatic sections of l-arginine-treated rats observed by L/M were supported by the E/M results, where there were dilatation of rER, numerous cytoplasmic vacuoles, depletion of zymogen granules, swollen mitochondria, intended nuclei, and interstitial inflammatory infiltrate. These results were in agreement with other investigators [22],[23] and could be explained by release of proinflammatory cytokines such as TNF-a, which causes mitochondrial damage as previously reported by Saitoh et al. [24]. In addition, the dilatation of rER could be attributed to formation of oxygen-derived free radicals, which induced lipid peroxidation within plasma and organellar membrane attacking the double bond in unsaturated fatty acids resulting in extensive membrane damage [25].

The presence of multiple cytoplasmic vacuoles in pancreatic acinar cells of the l-arginine-treated group in both L/M and E/M levels of this study was in agreement with other researchers [26] who attributed the appearance of these vacuoles to the presence of vacuole membrane protein 1. They added that this vacuole membrane protein 1 appears in the acinar cells during the early stages of AP causing cytoplasmic vacuolation followed by cell death.

The nuclear indentation observed in this study could be due to breakage of chromatin into short segments secondary to endonuclease activation due to ATP depletion, which is considered a reason of nuclear pyknosis [21].

The mechanism by which l-arginine induced AP is through inhibition of polyamine synthesis that inhibits nucleic acid and protein synthesis; as protein metabolism is most active in pancreatic acinar cells, it is likely that acinar cells are the first target of an arginine overdose, resulting in degradation or necrosis [27].

Inflammatory cytokines and neutrophil-mediated oxidative stress have a central role in the pathogenesis of AP induced by l-arginine, and the compounds that combat inflammation and oxidative stress ameliorate AP [28].

The inflammatory reaction observed after 24 h of l-arginine injection and its persistence for 1 week in this study could be explained by the lipid peroxidation and accumulation of oxygen-derived and nitrogen-derived free radicals. These free radicals play an important role in the development of local inflammation and systemic complications during AP. Lipid peroxidation causes damage to the lipid membranes, structural and enzymatic proteins, and DNA of the cells leading to loss of the membrane fluidity and integrity, leading to cell death [29]. These free radicals are important mediators of pancreatic tissue damage, as they arise from damaged mitochondria, activation of xanthine oxidase, nitric oxide synthase (NOS), and oxidation of xenobiotics by cytochromes P450 and activated polymorphonuclear leukocytes. Once produced, they directly attack biological membranes and stimulate arachidonic acid metabolism with increased production of prostaglandins, thromboxane, and leukotrienes [30]. They also trigger the accumulation of neutrophils and their adherence to the capillary wall with occurrence of edema in the pancreatic tissue. The same finding was observed in this study and was in agreement with others [31] who suggested that the lipid peroxidation products caused a damage to the membranes of endothelial cells of the blood capillaries, resulting in an increase of vascular permeability leading to inflammatory infiltrate and edema of the pancreatic interstitium.

The vascular congestion, edema, and extravasation of blood among pancreatic acini observed in this study could be explained by accumulation of nitric oxide (NO). This NO is produced by the activity of NOS enzyme, which is involved in regulation of the rate of perfusion of the pancreatic microvessels. The excess arginine can induce NOS activity, which results in high tissue levels of NO that might cause a direct toxic effect on pancreatic acinar cells, increasing of the vascular congestion, vascular permeability, and occurrence of pancreatic edema; such explanation was in agreement with other researchers [32]. Another explanation was reported by others [33] who stated that the l-arginine is a semiessential amino acid found in our diet as a precursor of NO, which is formed from l-arginine via the enzyme NOS. NO is a powerful vasodilator as it prevents the vascular smooth muscle proliferation, increasing the blood flow and congestion.

Masson trichrome-stained sections of this study revealed excess collagen fibers around congested blood vessels and in the area of inflammatory reaction in the l-arginine treated group. This result was in agreement with the result of other workers [34] and explained that the release of free radicals were associated with fibrosis of the pancreas [35]. They added that the pancreatic stellate cells play an important role in the development of pancreatic fibrosis, the same as reported by others [36,37] who showed that the free radicals generated by xanthine oxidase, which are involved in various forms of tissue injuries, directly activate pancreatic stellate cells leading to fibrosis. However, the exact mechanism of development of pancreatic fibrosis had not been fully elucidated.

The pancreatic acinar cells are highly specialized for digestive enzyme synthesis, storage, and secretion; therefore, they have abundant endoplasmic reticulum to meet the protein synthesis rate, the highest among all adult human tissues [38].

The decrease of basal basophilia of pancreatic acinar cells observed in this study could be explained by disruption of the normal structure and dilatation of rER that occupy the basal region of pancreatic acinar cells. This was confirmed by the E/M results of this study and other study that revealed dilatation of rER after l-arginine injection [39].

The decreased number of zymogen granules in this study in the l-arginine-treated group was explained previously by sustained increase of the cytosolic calcium, which leads to sustained increase of nuclear calcium with subsequent inhibition of calcium-induced gene transcription. This would inhibit the secretory function of pancreatic acinar cells and cause disruption of apical exocytosis as previously reported by other researchers [28],[40].

Numerous antioxidants have recently been examined for their protective properties against oxidative damage in AP and have been shown to moderate the changes in several parameters of the disease [41].

Pentoxifylline is a methylxanthine derivative that exhibits marked anti-inflammatory effect by inhibiting cytokine production. It may possibly act as a radical scavenger and/or reduce the production of reactive oxygen species from activated leukocytes. In the present study, the l-arginine and pentoxifylline-treated group (group III) showed improvement of the histological picture of pancreatic acini in both L/M and E/M levels compared with the l-arginine-treated group. This ameliorating effect of pentoxifylline supplementation became more obvious after 1 week. These results were in agreement with those of other researchers [42],[43],[44]. They reported that pentoxifylline reduced pancreatic inflammation, edema, and infiltration of inflammatory cells of pancreatic tissue by inhibiting cytokine production.

The beneficial effects of pentoxifylline are partially dependent on its regulatory effects on microvascular blood flow by inhibiting platelet aggregation and reducing blood viscosity [44].

In contrast to the result of the present work, Bassi et al. [45] denied the protective effect of pentoxifylline in severe AP induced in rats and their results were explained by others [42] on the basis of use of supramaximal dose of cerulein and intraductal infusion of glycodeoxycholic acid for induction of AP.

Masson trichrome-stained sections of the l-arginine and pentoxifylline treated group for 24 h and for 1 week revealed traces of collagen fibers deposited around blood vessels and in-between pancreatic lobules nearly the same as control. This was in agreement with others [46],[47] who reported that pentoxifylline has antifibrotic properties through inhibition of stellate cell activation, thus reducing the fibrosis [Table 1] and [Figure 7].
Figure 7: (a) An electron micrograph of pancreatic acinar cells of the control group showing basal rounded vesicular nuclei (N) with prominent nucleoli (n), apically situated electron-dense zymogenic secretory granules (Z), and packed cisternae of rough endoplasmic reticulum (rER). There is also short microvilli protruded through the lumen (L) of the pancreatic acinus. Notice lateral interdigitations of plasma membrane of adjoining cells (→) (×1000). (b) An electron micrograph of pancreatic acini of group IIA showing that pancreatic acinar cell (center) has indented nucleus (N), dilated cisternae of rough endoplasmic reticulum (rER), and few apical zymogen granules (Z). Dilated acinar lumen with irregular short microvilli and electron-dense particles (L) is also seen. Notice also normal acinar cell (upper right) with euchromatic nucleus, packed cisternae of rough endoplasmic reticulum, and secretory granules (×1000). (c) An electron micrograph of pancreatic acinar cells of group IIB showing two degenerated cells (left side) having indented nuclei (N), dilated cisternae of rough endoplasmic reticulum (rER), and few zymogen granules (Z). Other cell (center) shows small eccentric nucleus (n), cytoplasmic vacuoles (V), and no secretory granules (×1000). (d) An electron micrograph of pancreatic acinar cells of group IIIA showing nearly normal acinar cell (right side) with basal rounded euchromatic nucleus (N) and apical zymogen granules (Z). Left cell showing dilated cisternae of rough endoplasmic reticulum (rER) and few secretory granules. Notice congested blood vessel (BV) in-between the acini (×1500). (e) An electron micrograph of pancreatic acinar cell of group IIIB showing nearly normal acinar cell with basal rounded vesicular nucleus (N), numerous zymogen granules (Z), mitochondria (M), and packed cisternae of rough endoplasmic reticulum (rER) (×2000). (f) An electron micrograph of pancreatic acinar cell of group IV showing normal pancreatic cells with basal rounded vesicular nuclei (N), regularly arranged rough endoplasmic reticulum (rER), normal mitochondria (M), and abundant zymogen granules (Z) (×1500).

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Table 1: Differences in secretory granules between studied groups

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  Conclusion Top


l-arginine induced histological and ultrastructural changes in the pancreatic acinar cells and these changes were ameliorated by coadministration of pentoxifylline with l-arginine. Hence, use of pentoxifylline as adjuvant treatment with l-arginine is recommended to reduce the occurrence of AP.


  Acknowledgements Top


Conflicts of interest

There are no conflicts of interest.

 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
 
 
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