Secretory and vascular effects of the optical isomers of nicardipine.

The effects of optical isomers of nicardipine on the secretion of pancreatic juice and blood flow were investigated in the dog-isolated, blood-perfused pancreas. Intra-arterial administration of (-)-nicardipine (10-300 micrograms) caused a dose-dependent increase in pancreatic secretion. However, the (+)-isomer was much less potent than the (-)-isomer and even in 300 micrograms of (+)-isomer caused only a slight secretion. (+)- And (-)-nicardipine increased perfusion blood flow in a dose-dependent manner, and (+)-nicardipine was approximately five times as potent as the (-)-isomers. The maximum increase in a flow rate was produced by 30 micrograms of (+)-isomer and 100 micrograms of (-)-isomer. Bicarbonate concentration in pancreatic juice induced by (-)- and (+)-nicardipine was increased in a dose-dependent manner, but the protein concentration was only increased slightly. From these results, it is concluded that there is a stereoselectivity in the secretory and vascular actions of optical isomers of nicardipine.