The endocrine regulation of exocrine pancreas in preruminant milk-fed calves

Fifteen male Holstein X Frisian calves, weighing 65 +/- 3 kg and fed a milk replacer twice daily were fitted with a return cannula loop, chronically implanted at 10 days of age in the pancreatic duct, were used. In six successive experiments we have observed the influence of an intravenous infusion of secretin, cholecystokinin pancreozymin (CCK-PZ), vasoactive intestinal peptide (VIP), glucagon, gastrin and somatostatin on pancreatic juice flow rate, and on the excretion of proteins, calcium, inorganic phosphorus, zinc and amylase activity of pancreatic juice. In two other experiments, we have studied the interaction of secretin (or CCK-PZ) with somatostatin (SRIF). Each experiment was performed 5 h after calves feeding and no milk was given to the animals during the time of sampling. Our results indicate that the endocrine regulation of the exocrine pancreas in young calves is similar to that described in other mammals. Secretin and CCK-PZ increased significantly excretion of water, calcium, magnesium, inorganic phosphorus, zinc, proteins and amylase activity. Somatostatin and glucagon inhibited effects observed with two precedent hormones. Gastrin increased pancreatic juice flow rate but excretion of protein and amylase activity do not varied significantly. VIP showed no significant effect on pancreatic excretion of water, minerals, proteins and amylase activity. However, our animals seem to be characterized by a more intense excretion of proteins and amylase in the pancreatic juice following secretin than after CCK-PZ infusion.