RELATIVE INFLUENCE OF AMOUNT OF DIETARY ZINC AND INFUSION OF PROTEIN INTO THE DUODENUM ON THE AMOUNT OF ZINC IN BILIARY PANCREATIC SECRETIONS

A series of studies were undertaken to determine the relative influence of dietary Zn vs the presence of protein in the duodenum on the excretion of Zn in biliary/pancreatic fluid (B/P) of rats. Animals were fed diets ranging from 10 to 300 mg Zn/kg diet for 7 weeks and then fasted and cannulated for bile or B/P fluid collection. Secretions of fasted rats were collected 0.5 hr and then egg white was infused into the gut and stimulated secretions were collected. Elevated dietary Zn slightly increased Zn and decreased Cu content of B/P fluid but did not alter protein concentration or activity of carboxypeptidase A or B. In contrast, duodenal stimulation greatly increased Zn and protein content and activity of carboxypeptidase A and B. In a separate experiment, animals fed 10 or 300 mg Zn/kg diet were similarly cannulated and infused with protein at intervals from 6 to 240 hr following injection of Zn-65. Dietary Zn slightly elevated B/P Zn but did not alter biliary Zn concentration. Maximal biliary Zn output occurred 6 hr after injection whereas B/P Zn output was maximal after 12 hr. These results suggest that the Zn in B/P secretions of rats is there primarily as a result of metabolic demand by the pancreas, and these secretions are not a major means of maintaining Zn homeostasis.