Acinar Cell Vacuolization Research Articles

A New Animal Model of Reversible Acute Pancreatitis

Numerous animal models of acute pancreatitis are utilized to assess pathophysiologic events and to evaluate therapeutic options. However, none of the small animal models simulates reversible biliary pancreatitis with long-term follow-up (weeks). The present study was designed to create a reversible model of acute biliary pancreatitis in small experimental animals. Male Sprague–Dawley rats were subjected to laparotomy, and the common bile duct was dissected free at its junction to the duodenum. Experimental animals had a polypropylene tie occluder passed around the common bile duct and brought out through a separate stab wound in the abdominal wall. The duct was occluded for 24 hr; the blockage was then relieved and the tie withdrawn from the animal. Sham-operative animals had similar surgical procedures but without the occluder. Serum amylase values on Days 1 and 2 following surgery were significantly increased in the experimental group, but were not different from those of control animals on Day 3 or 4, suggesting reversibility of this biliary pancreatitis model. Likewise, serum bilirubin levels were increased in the experimental group on Days 1 and 2. Histologic analysis revealed edema, zymogen degranulation, inflammatory infiltration, vacuolization of acinar cells, and focal areas of fat and parenchymal necrosis in the experimental group. Only mild edema was observed in the sham-operative controls due to surgical manipulation. Pancreatic tissues obtained at 1 week postinduction of pancreatitis showed near total destruction of the architecture and dissolution of zymogen granules; in contrast, histology at the 3rd week showed almost normal-appearing pancreas with return of zymogen granules, suggesting recovery from the acute pancreatitis. This reproducible and reversible model of acute pancreatitis in the rat will provide for further studies in the pathogenesis of pancreatitis and its therapeutic interventions.

Edema and intrapancreatic trypsinogen activation precede glutathione depletion during caerulein pancreatitis.

Acute pancreatitis is characterized by hyperamylasemia, pancreatic edema, and the presence of activated digestive enzymes within the pancreas. The secretagogue-induced model of acute pancreatitis is also characterized by pancreatic acinar cell vacuolation, subcellular redistribution of lysosomal hydrolases, and a fall in pancreatic glutathione levels. We have performed time-dependence studies to determine the sequence with which these phenomena appear and to establish their cause-and-effect relationship. Evidence of lysosomal enzyme redistribution and trypsinogen activation within the pancreas could be detected within 10-15 min of the onset of supramaximal secretagogue stimulation, while hyperamylasemia (30 min), pancreatic edema (60 min), and acinar cell vacuolation (60 min) occurred at later times. Pancreatic glutathione levels were either unchanged (15 and 30 min) or elevated (60 min) during the early times of supramaximal stimulation and were only noted to be decreased at a later time. These results support the conclusion that intrapancreatic digestive enzyme activation, possibly occurring by a mechanism involving lysosomal hydrolase redistribution, is an early and likely a critical event in the evolution of secretagogue-induced pancreatitis but that glutathione depletion is neither early nor critical to the evolution of this model of pancreatitis.

Effects of nafamostat mesilate, somatostatin, and glucagon on caerulein-induced acute pancreatitis in rats

The inhibitory effects of somatostatin (SMS) and glucagon (Gn) on acute pancreatitis were evaluated in an experimental acute pancreatitis model in male Wistar rats. The effects of these agents were compared with those of nafamostat mesilate (NM). The acute pancreatitis was induced by four serial subcutaneous injections of caerulein. The rats were divided into four groups. The first group (n=28) received SMS daily, the second group (n=28) received Gn daily, and the third group (n=28) received NM daily after the first injection of caerulein. The fourth group (n=42) received caerulein alone and served as the control group. Animals were sacrificed 4, 6, 8, 12, and 24 h, and 3 and 7 days after the first administration of caerulein and the degree of severity of the acute pancreatitis was evaluated by serial morphological and histological examinations of pancreatic tissues, as well as in terms of the serum concentrations of amylase and lipase. The characteristic findings of acute pancreatitis in the animals of all groups treated with SMS, Gn, or NM were markedly attenuated at all time points after the treatments compared with findings in the controls (caerulein alone) in terms of wet weight of pancreas, serum concentrations of amylase and lipase, formation of intracellular vacuoles in acinar cells, interstitial edema, and infiltration of an inflammatory cell component. The inhibitory effects of SMS, Gn, and NM on acute pancreatitis were similar at the doses used. These results suggest that SMS and Gn are as useful as NM, they may be of value for the treatment of acute pancreatitis.

The protective effects of long-acting recombinant human pancreatic secretory trypsin inhibitor (R44S-PSTI) in a rat model of cerulein-induced pancreatitis.

The effects of pancreatic secretory trypsin inhibitor (PSTI) on cerulein-induced pancreatitis were studied in a rat model. Arg44 of PSTI was replaced by Ser using site-directed mutagenesis (R44S-PSTI). R44S-PSTI has a longer half-life than the natural form. Pancreatitis was induced by four intramuscular injections of cerulein (50 microgram/kg at 1 h intervals). Continuous intravenous infusion of R44S-PSTI began at a dose of 20 micrograms/kg/h 30 min before the first cerulein injection, and was completed 3 h after the last cerulein injection. Tumour necrosis factor (TNF-alpha) production by isolated peritoneal macrophages from rats with cerulein-induced pancreatitis increased following lipopolysaccharide stimulation, compared to control rats (P < 0.01). R44S-PSTI administration significantly decreased the TNF-alpha production by peritoneal macrophages from rats with cerulein-induced pancreatitis (P < 0.05). In addition, R44S-PSTI significantly reduced serum amylase activity (P < 0.01) and pancreatic wet weight after pancreatitis induction (P < 0.05). Histological examination revealed marked acinar cell vacuolization, interstitial oedema, and cellular infiltration in cerulein-induced pancreatitis, but a lesser degree of histological change in rats that were treated with R44S-PSTI. Prophylactic use of intravenous R44S-PSTI infusion may reduce the severity of acute pancreatitis either histologically or serologically.

Presence of curarizing polypeptides and a pancreatitis-inducing fraction without muscarinic effects in the venom of the venezuelan scorpion tityus discrepans (karsch)

Four toxic polypeptidic fractions (TdF-I–IV) were purified from the venom of the Venezuelan scorpion Tityus discrepans by means of gel filtration on Sephadex ® G-50. The peptides have mol. wts of approx. 6000 and normalized elution volumes ( V n = Elution volume/Total column volume) of: TdF-I = 0.27 (0.26, 0.28), n = 13; TdF-II = 0.40 (0.39,0.41), n = 15; TdF-III = 0.57 (0.56, 0.59), n = 14, and TdF-IV = 0.68 (0.67, 0.70), n = 13 (median and its 95% confidence interval, n = number of elutions used to calculate the median). Mice (white, male, 16–19 g, IVIC strain) were injected with these fractions and sacrificed 48 hr later. No toxicity was observed when fraction I (0.93 μg/g mice) or IV (2.51 μg/g mice) was injected i.p. into mice. TdF-II (9 to 50 μg/g mice) produced sialorrhea, dyspnea and death 1 hr after i.p. injection. Light microscopy of the pancreas revealed that TdF-III (3.42 μg/g mice) produced structural modifications such as acinar cell vacuolization, degranulation and interstitial swelling; these changes are characteristic of acute pancreatitis. No effects on the islets of Langerhans or the pancreatic ducts were observed. TdF-III had no overt muscarinic effects when injected i.p. into mice. On the neuromuscular preparation of the frog ( Hyla crepitans) TdF-I blocked neuromuscular transmission at the postsynaptic membrane; TdF-II depolarized the muscle membrane by opening sodium channels and TdF-IV prolonged action potentials, suggesting potassium channel blockage.

Ultralstructural and biochemical studies of the effect of polychlorinated biphenyl on mouse parotid gland cells

These effects of polychlorinated biphenyl (PCB) were examined by light and electron microscopy and biochemical analysis of lysosomal enzyme activities. Several experimental protocols with dosage schedules of either 0.2, 2.0, or 20 mg/kg of PCB were used. Typical histological changes were observed in mice given 2 mg/kg of PCB in a single injection. There were no remarkable changes until 4 days after PCB administration; marked cytoplasmic vacuolation was observed in parotid acinar cells at 7 days. The activities of lysosomal enzymes increased after the PCB injection and their maximum values appeared consistently at 4 days after the treatment; the increases were threefold for acid phosphatase, twofold for β-glucuronidase, threefold for cathepsin D, fivefold for cathepsin H and twofold for cathepsin L. As vacuolation was preceded by a large increase in lysosomal enzyme activities and the vacuoles co-localized with lysosomes, it is suggested that an increase in these activities induced by PCB may be closely related to the development of vacuolation in the parotid acinar cells as a subacute effect of PCB.

Ligation-Induced Acute Pancreatitis in Rats and Opossums: A Comparative Morphologic Study of the Early Phase

Bile and pancreatic duct ligation (BPDL) in rats does not induce severe acute pancreatitis but only mild inflammation, which is self-limiting and eventually leads to pancreatic atrophy. However, BPDL in opossums induces severe acute necrotizing pancreatitis which uniformly leads to death within 14 days. We compared pancreatic morphologic changes after 24 hr of BPDL in rats and opossums. Pancreatitis histology score and acinar cell ultrastructural changes were evaluated. In both species, BPDL was associated with significant increases in histology score compared to sham controls (5.0 ± 0.3 vs 1.5 ± 0.3 in rats, 5.3 ± 0.4 vs 1.1 ± 0.1 in opossums; mean ± SEM, ANOVA, P < 0.05). However, there was no significant difference in histology score between rats and opossums following BPDL; histologic changes, such as white blood cell infiltration, acinar cell vacuolation, and focal acinar cell necrosis, were similar. Acinar cell ultrastructural changes after BPDL in both species included dilated endoplasmic reticulum and autophagic vacuole formation. These findings indicate that the early morphologic changes after BPDL in rats are quite similar to those seen early in the course of BPDL-induced acute necrotizing pancreatitis in opossums. As the rat is a more economical and convenient model to study than the opossum, this study supports the use of the rat model to conduct pilot studies of early events in the development of BPDL-induced acute pancreatitis. This study also suggests the potential for investigating mechanisms that may be present in the rat which protect against progressive and fatal acute necrotizing pancreatitis as observed in opossums after longer periods of BPDL.

Early ductal decompression prevents the progression of biliary pancreatitis: An experimental study in the opossum

Background: The value of early endoscopic or surgical interventions to remove bile duct stones and decompress the biliopancreatic ductal system in gallstone pancreatitis is controversial. Methods: To evaluate this issue, acute hemorrhagic necrotizing pancreatitis was induced in opossums by obstructing the biliopancreatic ductal system with a balloon catheter for 1, 3, or 5 days. Results: A progressive increase in the severity of pancreatitis, as manifested by inflammation, fat necrosis, hemorrhage, acinar cell vacuolization, in vitro lactate dehydrogenase release, and acinar cell necrosis, was noted in these obstructed animals. In contrast, decompression of the obstructed ductal system by removal of the balloon catheter after 1 or 3 days prevented the increase in severity of these parameters of pancreatic injury. Conclusions: We conclude that the severity of biliary pancreatitis in this model is dependent upon the duration of ductal obstruction and that decompression of the ductal system can prevent progression of the disease. These observations support the practice of early attempts to remove obstructing stones in clinical gallstone pancreatitis.

Severe subcellular damage in the rat exocrine pancreas after pancreatobiliary diversion.

Cholecystokinin (CCK) may contribute to the genesis of both pancreatic carcinoma and acute pancreatitis. By transposing a long segment of jejunum to lie between the pylorus and the duodenal papilla, pancreatobiliary diversion (PBD) causes a persistent increase in circulating CCK levels, as the normal feedback inhibition of jejunal CCK release by pancreatic juice is evaded. A number of morphological, physiological, and acinar cytokinetic changes ensue. This investigation has examined the ultrastructural changes in pancreatic acinar cells after PBD in the presence and absence of CR1409 (lorglumide), a CCK receptor antagonist. After 14 days there was degranulation and vacuolation of acinar cells with involvement of the enzyme acid phosphatase. The presence of morphologically distinct extracisternal acid phosphatase indisputably predisposed acinar cells to severe damage. Treatment with CR1409 largely prevented degranulation after PBD, but vacuolation of acinar cells still occurred, indicating a possible toxic effect of the receptor antagonist. This is the first report of CCK itself, rather than one of its analogues, causing in vivo pancreatic damage that is generally considered as a forerunner to acute pancreatitis. This is of fundamental importance to the understanding of the earliest stages of the disease.

Chronic alcohol consumption intensifies caerulein-induced acute pancreatitis in the rat

Rats were chronically fed either an ethanol-containing diet (36% of total calories derived from alcohol) or a pair-fed, control diet (no alcohol) for 8 wk, and acute pancreatitis (AP) was subsequently induced by a 3-h i.v. infusion of caerulein (CR) at a dose of 5 micrograms/kg/hr. CR-induced AP in control rats (no alcohol) was characterized by a significant elevation in serum lipase content, pancreatic interstitial edema, infrequent occurrences of karyorrhexis, and the appearance of vacuoles in acinar cells. Chronic feeding of the ethanol diet followed by treatment with CR resulted in increases in serum lipase content, interstitial edema, karyorrhexis, and acinar vacuolization that were significantly greater than that seen in rats fed the control diet and treated with CR. It is concluded that chronic ethanol intake in the rat intensifies AP that is subsequently induced by CR.

Monoclonal antibody to a common antigen of secretory granule membranes: intracellular localization and recycling of the antigen after secretion.

Monoclonal antibody (MAb) 170-5 was generated to the secretory granule membrane of rat parotid acinar cells. The MAb recognized integral membrane glycoproteins (SG 170 antigen) localized on the luminal side of the secretory granules with N-linked carbohydrates, molecular weights 92, 84, 76, 69, and 65 KD. Immunohistochemical studies indicated that the SG 170 antigen was found in the secretory granules of both exocrine and endocrine cells and in the lysosomes of various cells in the rat. Immunoelectron microscopy with immunogold revealed that the antigen was present on the membrane of the secretory granules, lysosomes, the Golgi vesicles, and condensing vacuoles in pancreatic and parotid acinar cells and in AR42J rat pancreatic tumor cells; the Golgi stacks exhibited no immunoreaction. The common localization of the antigen in the secretory granule membranes indicated that this antigen may play an essential role in regulated secretion. Employing HRP-labeled MAb 170-5, we followed the retrieval of the antigen after exocytosis in AR42J cells. The MAb was internalized specifically with antigen-mediated endocytosis. It was transported to endosomes, subsequently to the trans-Golgi network, and then packaged into secretory granules. However, the Golgi stacks revealed no uptake of the labeled antibody.

Protective Effect of Human Pancreatic Secretory Trypsin Inhibitor on Cerulein-lnduced Acute Pancreatitis in Rats

We examined the protective effect of human pancreatic secretory trypsin inhibitor (PSTI), a specific trypsin inhibitor secreted from pancreatic acinar cells into the pancreatic duct, on cerulein-induced acute pancreatitis in conscious rats. The protective effect of human PSTI-RS, an analogue of PSTI with Arg-44 to Ser substitution which has a longer half-life in vitro, was also examined. Intraperitoneal administration of a pharmacological dose of cerulein to conscious rats induced acute pancreatitis, characterized by light microscopy as cellular disorganization of the acini and interstitial edema. Intravenous infusion of human PSTI (10, 50 or 250 micrograms/rat/h) into rats with cerulein-induced acute pancreatitis decreased their pancreatic wet weight and plasma amylase concentration. It also caused a dose-dependent decrease in vacuoles in acinar cells and interstitial edema. Human PSTI-RS, which has a longer half-life in vivo, was more effective than native PSTI at the same dose rate (10 micrograms/rat/h) in reducing pancreatitis. These results suggest that human PSTI may have a beneficial effect on acute pancreatitis.

Effects of positive end-expiratory pressure (PEEP) ventilation on the exocrine pancreas in minipigs

The effect of positive end-expiratory pressure (PEEP) ventilation on the pancreas was studied in 22 anesthetized minipigs. Five pigs were treated with intermittent positive pressure ventilation (IPPV) for 21 h (Group I) and six pigs were treated with a PEEP of 15 cm H2O for 21 h (Group II). We next explored the influence of PEEP ventilation while stimulating the pancreas with Ceruletide, a synthetic cholecystokinin (CCK) analog, at 2.3 micrograms/kg per h.i.v. for 3 h. Ventilation with IPPV for 4 h (n = 5, group III) was compared with PEEP of 15 cm H2O for 4 h (n = 6, group IV). Changes in serum-lipase were observed in all groups. The average lipase level rose from 12.6 U/l to 67 U/l group I and from 15.1 U/l to 129.2 U/l in group II (P = 0.025 for group I vs group II). In group IV (PEEP and Ceruletide), the mean lipase level rose about six times more than in group III (IPPV and Ceruletide). The difference was significant (P less than 0.00005). By three-factor ANOVA analysis, effects due to the drug (P less than 0.000006) and to PEEP (P less than 0.038) as well as a threefold interaction could be demonstrated, i.e., using Ceruletide a greater PEEP effect on lipase than without the drug (P less than 0.023) took place. There were no significant histological changes of the pancreas in groups I and III. In group II (21 h PEEP), vacuolization of acinar cells was evident; on the ultrastructural level, indication was given that these vacuoles derived both from the Golgi apparatus and from fusion of individual zymogen granules. In group IV (PEEP and Ceruletide), the focal appearance of fatty-tissue necrosis and acinar cells as well as hemorrhage of the gland was observed. We conclude that PEEP ventilation impairs the function of the pancreas and produces even more deleterious effects when the gland is stimulated. These effects should be considered when PEEP is used in clinical practice in the treatment of acute pancreatitis.

Adverse Effect of Therapeutic Vasoconstrictors in Experimental Acute Pancreatitis

Alpha-adrenergic drugs commonly are used to treat hypotension resulting from severe acute pancreatitis. It was shown previously that although systemic arterial pressure is increased by phenylephrine, pancreatic microcirculatory perfusion is decreased. Because inadequate tissue perfusion may be critical in the progression of edematous pancreatitis to parenchymal necrosis, it was hypothesized that vasoconstrictors might be harmful in pancreatitis. Therefore the effect of phenylephrine on cerulein-induced mild pancreatitis were studied. Sprague-Dawley rats (n = 54) were randomly allocated to 6 experimental groups and subjected to the following infusion regimens: (1) cerulein (cae) + phenylephrine (phe), (2) cae + saline (NS), (3) NS + phe, (4) cae + phenoxybenzamine (pbz) + phe, (5) NS + pbz + phe, and (6) NS. Initial and terminal hematocrit, serum amylase activity, and blood ionized calcium concentration were determined. The animals were killed 9 hours after starting the infusion. Macroscopic and histologic changes were scored by a 'blinded' pathologist. Phenylephrine increased the severity of cerulein-induced pancreatitis as manifested by statistically significant adverse changes in serum amylase, hematocrit, ionized calcium, peripancreatitic soap formation, and acinar cell vacuolization. These changes were antagonized by alpha-adrenergic receptor blockade with phenoxybenzamine. It is concluded that phenylephrine is deleterious in acute experimental pancreatitis, the first demonstration of such an effect by a pharmacologic vasoconstrictor, and suggested that microcirculatory changes may be important in the transition of mild to severe pancreatitis. Caution in the use of vasoconstrictor drugs in patients with acute pancreatitis is recommended.

Beneficial effects of the synthetic trypsin inhibitor camostate in cerulein-induced acute pancreatitis in rats

The therapeutic effect and the mechanism of action of the synthetic trypsin inhibitor camostate were studied in a rat model of acute interstitial pancreatitis induced by four subcutaneous injections of 20 micrograms/kg body weight of cerulein at hourly intervals. Rats with acute pancreatitis were given either 100 mg/kg body weight camostate or volume- and pH-adjusted water via an orogastric tube 30 min after the last cerulein injection. The elevation of serum amylase activity was significantly reduced by camostate treatment and the peak value was seen 1 hr earlier than that observed in the rats that did not receive camostate. Camostate also inhibited the reduction in pancreatic content of lipase and amylase seen during experimental pancreatitis. These effects were accompanied by alleviation of the histologic signs of acute pancreatitis such as cellular infiltration and acinar cell vacuolization. After oral administration, camostate and its metabolite were absorbed from the intestine and were detectable in plasma for more than 6 hr in concentrations high enough to have antiprotease activity. In addition, camostate in the duodenum was able to increase pancreatic juice flow and protein output and to stimulate endogenous secretin release. These results suggest that oral administration of camostate reduces the severity of cerulein-induced acute pancreatitis by releasing endogenous secretin and by its antiprotease activity.

Failure of a Potent Cholecystokinin Antagonist to Protect Against Diet-Induced Pancreatitis in Mice

The effects of a potent cholecystokinin (CCK) receptor antagonist, L-364,718, on two forms of experimental acute pancreatitis in mice were evaluated. The antagonist prevented the hyperamylasemia, pancreatic edema, and acinar cell vacuolization that followed administration of a supramaximally stimulating dose of the cholecystokinin analogue cerulein. In contrast, the same dose of L-364,718 (1 mg/kg/6 h) and an even higher dose (10 mg/kg/6 h) failed to prevent the hyperamylasemia, acinar cell necrosis, and mortality that followed administration of a choline-deficient ethionine-supplemented diet. These observations are at variance with those previously reported to follow administration of the relatively weak cholecystokinin antagonist proglumide (Niederau C et al. J Clin Invest 1986;78:1056-63). The observations reported in this communication suggest that cholecystokinin does not play an important role in diet-induced pancreatitis and that CCK receptor antagonists are unlikely to be of benefit in the treatment of clinical acute pancreatitis.

Regression of autophagic vacuoles in house pancreatic cells: A morphometric study of the effect of methylamine and chloroquine followed by cycloheximide treatment

Treatment of mice with methylamine and chloroquine for two hours markedly increased the volume fraction of autophagic vacuoles in the pancreatic acinar cells of the mouse. The autophagic vacuoles disappeared, from the cells within 20 min after the administration of a suppressor of autophagic sequestration cycloheximide to animals pretreated with 0,25 mg b.w. dose of methylamine. In contrast, no regression or very slow decay was seen in cells of mice pretreated with higher doses of methylamine (0,50-0,70 mg/g b.w.) and chloroquine (0,08 mg/g b.w.). Our data show that the two drugs retard the disintegration of autophagic vacuole content. It is concluded, that accumulation of autophagic vacuoles due to their slow turnover is an important mechanism of the expansion of autophagic vacuole compartment under the effect of methylamine and chloroquine.

The effects of nafamostat mesilate (FUT-175) on caerulein-induced acute pancreatitis in the rat.

We examined the ability of a highly potent synthetic protease inhibitor, nafamostat mesilate (FUT-175), to protect the rat pancrease against AP induced by a supramaximal dose of caerulein (CR). Rats received a 6-h, continuous intravenous (iv) infusion of either CR alone or CR + a 6-h infusion of either 2.5, 5.0, 10.0, 25.0, or 50.0 mg of FUT-175/kg/h. Pancreas weights and serum chymotrypsinogen concentrations were significantly elevated by approximately 85 and 75%, respectively, over values in saline infused rats. Pancreas weights in rats treated with CR + FUT-175 at doses from 2.5-25.0 mg/kg/h were significantly reduced by approximately 20% compared to rats given CR along, and histology showed a reduction in the extent and size of acinar cell vacuolization and reduced interstitial edema compared to rats treated with CR alone. Serum chymotrypsinogen concentrations in rats treated with CR and either 5.0 or 10.0 mg of FUT-175/kg/h were significantly lower than in rats given CR alone. Significant mortality occurred in rats infused with FUT-175 at doses of either 25.0 or 50.0 mg of FUT-175/kg/h. These data indicate that serine proteases appear to be involved in the pathogenesis of CR induced AP in rats and that FUT-175 administered in low doses (2.5-10.0 mg/kg/h) provides significant protection against this form of pancreatitis.

Esterase inhibitors prevent lysosomal enzyme redistribution in two noninvasive models of experimental pancreatitis

Earlier studies have indicated that lysosomal enzymes such as cathepsin B become redistributed within pancreatic acinar cells during the early stages of both diet- and secretagogue-induced acute pancreatitis. As a result, cathepsin B and digestive zymogens became colocalized within large cytoplasmic vacuoles. As cathepsin B can activate trypsinogen, this colocalization could result in intracellular digestive enzyme activation. The present study investigates the protective effects of gabexate mesilate (FOY) and camostate (FOY 305) on both of these noninvasive models of experimental pancreatitis. These esterase inhibitors prevented the hyperamylasemia, pancreatic edema, and acinar cell vacuolization that characterize secretagogue-induced pancreatitis and the hyperamylasemia and mortality that characterize diet-induced pancreatitis. In addition, FOY and FOY 305 were found to significantly decrease the subcellular redistribution of cathepsin B that occurs in both models. These findings indicate that enzyme activity sensitive to inhibition by FOY and FOY 305 may be critical to the redistribution phenomenon that characterizes both of these models of pancreatitis.

Localization of cathepsin B in normal and hyperplastic human prostate by immunoperoxidase and protein A‐gold techniques

Cathepsin B, a lysosomal cysteine protease, was localized in normal prostate and benign prostatic hyperplasia (BPH) using immunoperoxidase and protein A-gold techniques. Our objective was to determine whether cathepsin B was involved in the prostatic epithelium affected by nodular hyperplasia. All samples were collected immediately after prostatectomy. Immunohistochemical studies showed that the enzyme was expressed in the supranuclear cytoplasm of columnar cells and in numerous basal cells of normal and BPH acini. The strongest localization of cathepsin B occurred in acinar basal cells; hence, it is possible that cathepsin B could be useful as a marker for such cellular elements. Stromal macrophages showed reaction products, but lymphocytes and neutrophils did not. In both normal and hyperplastic glands, the enzyme was localized by gold particles in lysosomes, secretory granules, and vacuoles of columnar epithelial acinar cells. Immunoelectron microscopic study also showed the presence of cathepsin B in the heterochromatin (condensed chromatin) and nuclear membranes of columnar and basal cells, but not in euchromatin or nucleoli. At present, the function of cathepsin B in the nuclei of basal and columnar cells remains unknown. However, the cathepsin B in the cytoplasmic compartment might be associated with the lysosomal function of the cells. The role of cathepsin B as a marker for basal cell participation in the development of prostatic lesions should be studied further.