Abstract
Several investigations in vivo and in vitro have shown that gastro-intestinal hormones stimulate insulin secretion. However, the reports on the insulinotropic activity of pancreozymin are contradictory. The conflicting results are probably due to the fact that pure native preparation of this hormone has not been obtained in “physiologic” doses. In the present study this problem has been investigated by exposing rat pancreas to caerulein in vitro. Caerulein, an active decapeptide isolated from the skin of the Australian amphibia Hyla caerulea, resembles pancreozymin in chemical structure, including C-terminus. This active polypeptide of nonmammalian origin has been shown to possess all the biological activities of pancreozymin. The present investigation was undertaken to evaluate the significance of the interactions of exocrine and endocrine pancreas using perfused rat pancreas in vitro.
Biphasic insulin release was demonstrated with caerulein at concentrations higher than 1 ng/ml. Insulin response of the first phase was proportional to the dose up to 1 μg/ml. The second phase of insulin release was, however, almost constant, regardless of the concentrations of caerulein. Release of glucagon was stimulated by the same concentrations of caerulein which stimulated insulin release.
Maximal responses of the pancreatic amylase and pancreatic juice output were observed with 1 ng/ml of caerulein. With higher doses, significantly less secretory responses were observed. The dissociation of the response to caerulein between endocrine and exocrine pancreas was found.
