Effect of somatostatin on cholecystokinin-induced amylase release in rat pancreatic acini

The effect of somatostatin on cholecystokinin-induced amylase release was i nvestigated in isolated rat pancreatic acini, Acini were isolated by enzyma tic digestion and incubated in a HEPES buffered Ringer's solution with test ing reagents for 30 minutes at 37 degreesC. The activity of released amylas e, cAMP, and inositol phosphate formation were measured. Intracellular calc ium concentration ([Ca2+],) was also checked. Somatostatin 14 and octreotid e, a somatostatin analog, inhibited CCK-stimulated amylase release in a con centration-dependent manner. The inhibitory effect of octreotide on CCK-ind uced amylase release was not shown when the acini were treated with 8-Br-cA MP, irrespective of the presence of IBMX. Forskolin potentiated CCK-induced amylase release and this effect was blocked by octreotide treatment; altho ugh CCK-8 (3 x 10(-11) M failed to stimulate cAMP formation. oetreotide sig nificantly inhibited basal cAMP formation in the acini. The increase of [Ca 2+], in response to CCK was inhibited by octreotide. However, CCK-induced i nositol phosphate formation was not changed by 10(-9) il I octreotide. Octr eotide had no effect on CCK-stimulated tyrosine phosphorylation, and tyrosi ne phosphatase inhibitors (NaF and Na2WO4) did not influence the effect of octreotide on CCK-induced amylase release, From these results, we conclude that octreotide inhibits CCK-induced amylase release by inhibiting basal cA MP formation and decreasing the [Ca2+], stimulated by CCK.