AMINO-ACID TRANSPORT IN THE EXOCRINE PANCREAS .4. DO GLUCAGON OR INSULIN MEDIATE THE INVIVO EFFECT OF CERULEIN ON AMINO-ACID TRANSPORT AND INCORPORATION

The direct in vitro effect of caerulein on pancreatic protein synthesis and amino acid transport has been investigated. In contrast to in vivo conditions we were unable to demonstrate any effect on α-aminoisobutyric acid and leucine uptake and on leucine incorporation using rat pancreatic lobules. Insulin and glucagon were therefore examined as possible mediators for the in vivo effect of caerulein. Insulin (1-5 μM) slightly enhanced AIB uptake (16% but did not change uptake and incorporation of leucine. Glucagon (0.01-1 μM) was ineffective. Both islet hormones had no influence on the formation of cyclic GMP induced by secretion either in rat (40% increase) or in guinea pig lobules (500% increase). It seems unlikely that the two islet hormones exert any direct effect on the exocrine pancreas and thus could serve as mediators for the in vivo synthetic effect of caerulein.