Effect of cholecystokinin-pancreozymin on the nitric oxide synthase activity and cyclic GMP level in rat pancreatic tissue

In pancreatic cells, NO formation is associated with increased levels of cGMP and endocrine/ exocrine secretion. In the present study, the role of NO in the regulation of exocrine secretion was investigated in rat pancreatic tissues. Treatment of rat pancreatic tissue with cholecystokinin-pancreozymin (CCK-PZ) resulted in an significant increase in arginine conversion to citrulline, the amount of nitrite/nitrate, the release of amylase, and the level of cGMP. Furthermore, CCK-PZ-stimulated increase of amylase release and conversion of arginine to citrulline transformation were counteracted by the inhibitor of NO synthase, NG-nitro-L-arginine methyl ester. The results on the time course of CCK-PZ-induced citrulline formation and rise of cGMP level indicate that NO synthase and guanylate cyclase are activated within the first seconds of stimulation. The kinetics of citrulline accumulation correlate well with those of cGMP rise, which further confirms the conclusion that NO mediates the response to CCK-PZ by cGMP.