Effect of Diabetes Mellitus on the Regulation of Enzyme Secretion by Isolated Rat Pancreatic Acini

Abstract

A B S T R A C T The nature and mechanism of the pancreatic exocrine dysfunction in diabetes mellitus were evaluated in vitro using isolated pancreatic acini prepared from streptozotocin-induced diabetic rats. The content of amylase and ribonuclease in diabetic acini was -0.5 and 50% of the normal content, respectively. Further, reduced amounts of both enzymes were secreted by diabetic acini in response to both cholecystokinin (CCK) and carbamylcholine. However, when enzyme secretion was normalized relative to initial acinar contents, both normal and diabetic acini released enzymes at a comparable maximal rate. The time course of the release of these enzymes, and newly synthesized protein were similar in both acini. In normal acini, the effect of CCK was maximal at a concentration of 100 pM; higher concentrations led to submaximal enzyme release. The dose-response curve in diabetic acini was similarly shaped, but shifted threefold towards higher concentration. The mobilization of cellular Ca2" in response to CCK was also shifted.In contrast to these results with CCK, the dose-response curve to carbamylcholine was unaltered by diabetes. The observed effects were confirmed to be due to insulin deficiency and not due to direct toxic effect of streptozotocin on acinar cells or malnutrition. Streptozotocin had no acute effect on acini when measured 24 h after administration, and alloxan, another beta cell toxin, induced similar changes in acinar enzyme content and secretory response. Moreover, the administration of exogenous insulin to diabetic rats returned the content of pancreatic amylase and the secretory

Cholecystokinin bioactivity in human plasma. Molecular forms, responses to feeding, and relationship to gallbladder contraction.

“…Isolated pancreatic acini were prepared from 180-200-g female Sprague-Dawley rats by collagenase digestion of pancreas in KHB as previously described (27,28). Acini were then incubated with plasma extracts or standard CCK-8 concentrations for 30 min at 37°C (28).…”

“…Acini were then incubated with plasma extracts or standard CCK-8 concentrations for 30 min at 37°C (28). Amylase released into the medium was assayed using procion yellow coupled starch as substrate (29 Feeding and collection of plasma.…”

Pharmacological profile of TP‐680, a new cholecystokininA receptor antagonist

“…Amylase released into the extracellular medium during a 30 min incubation with various concentrations of secretagogues is expressed as a percentage of the total content of the enzyme present in the acinar pellet at the beginning of the incubation period (Otsuki & Williams, 1982 ure 5). Furthermore, the slope of the Schild regression line of TP-680 was 1.69, indicating that its mode of inhibition was not competitive.…”

Pharmacological Profile of KSG-504, a New Cholecystokinin-A-Receptor Antagonist

“…Rat pancreatic acini were prepared by the method of Otsuki and Williams (24). After isolating the rat pancreas, 5 ml of Krebs-Henseleit buffer (pH 7.35 at 25 C) containing 120 unit/ml of collagenase was injected into the tissue.…”