Abstract
The present investigation was undertaken to make clear the differences of the responsiviness of the rat exocrine and endocrine pancreas to caerulein in vivo and in vitro. Caerulein, an active decapeptide found in the skin of Australian amphibia Hyla caerulea, posesses remarkable similarities and biological activities to cholecystokinin-pancreozymin (CCK·PZ).
(1) Caerulein strongly stimulated the rate of flow and amylase output both in vivo and in vitro.
(2) The minimum doses which elicited the maximum secretion of the pancreatic juice and enzyme from the isolated and perfused rat pancreas and in vivo experiments were 0.05ng/ml and 10mg/ml/min, respectively.
(3) Supramaximal stimulation with caerulein resulted in significantly decreased pancreatic juice and enzyme secretion.
(4) Increase of insulin and glucagon were not observed by the doses which stimulated the rate of amylase output and flow of pancreatic juice, but they were elicited by only supramaximal dose of caerulein (more than 10ng/ml, in vitro and more than 100ng/kg/min, in vivo).
(5) Discrepancy of the effective dose of caerulein between on pancreatic exocrine and endocrine function was observed.
These results suggested that the exocrine responses of the pancreas may be due to the physiological effect of CCK·PZ, while the endocrine responses may be resulted from the unphysiological doses. It is important to differentiate the physiological effects from the pharmacological ones before coming to the condusion of the effects of G. I. hermones on the exocrine and endocrine pancreas.
