The Role of Intracellular Ca2+ in Inhibiting Somatostatin-Induced Pancreatic Amylase Release

Rhie, Duck Joo; Kim, Hye Won; Song, In Young; Yi, Sae Young; Yoon, Shin Hee; Hahn, Sang June; Sim, Sang Soo; Kim, Myung Suk; Jo, Yang Hyeok

Abstract

BACKGROUND/AIMS: We previously found that somotostatin (SS) inhibited amylase release partly by inhibiting basal cellular cAMP formation in pancreatic acini. In the present study, we verified the effect of SS on intracellular calcium pathway in pancreatic acini isolated from rats, using a synthetic SS analogue, octreotide. For that purpose, permeabilized acini were employed and intracellular calcium concentration ([Ca2+]i) was measured.
METHODS
Dispersed pancreatic acini were isolated from rat pancreas and amylase release was measured. Pancreatic acini were permeabilized using strep tolysin O (SLO) to maintain a constant optional [Ca2+]i. The [Ca2+]i was determined using fura-2/AM.
RESULTS
In SLO-permeabilized pancreatic acini, CCK-8 increased amylase release despite high [Ca2+]i. The increased amylase release was significantly inhibited by octreotide. In normal dispersed acini, amylase release stimulated by CCK-8 and carbachol was inhibited by octreotide. CCK-8 and carbachol significantly increased [Ca2+]i. However, Octreotide alone did not have any effect on [Ca2+]i. Increases in the [Ca2+]i induced by CCK-8 and carbachol were augmented by octreotide
CONCLUSIONS
From the above result, it is concluded that octreotide inhibits CCK-induced amylase release irrespective of intracellular calcium, and increased [Ca2+]i in response to octreotide is no related directly to inhibition of pancreatic amylase release.