Effect of rGRF on exocrine pancreatic secretion of the rat in vivo.

Human and rat GRFs have been reported to stimulate cAMP production and amylase release by guinea pig acinar cells in vitro, with different potencies. Previous reports indicated that hGRF had no effect on pancreatic secretion of the rat in vivo. In the present experiments, dose-response studies were made with rGRF, VIP and secretin on the pancreatic secretion of anaesthetized rats. All three peptides stimulated pancreatic secretion. rGRF induced a slight water and electrolyte secretion, with an efficacy about ten times smaller than secretin, and a potency about thirty times smaller. rGRF stimulated total protein output with the same efficacy as secretin and VIP, and with the same potency as VIP, that is about 100 times smaller than secretin. rGRF increased the concentration of total protein, but not that of bicarbonate in pancreatic juice. Maximal doses of VIP and rGRF did not show any additive effect. It is concluded that large doses of rGRF are able to stimulate the rat acinar cells in vivo, presumably through an interaction with VIP receptors.