The effect of varying dietary zinc levels on the concentration and localization of zinc in rat bile-pancreatic fluid.
To determine if zinc homeostasis occurs by zinc output from bile-pancreatic secretions, the bile-pancreatic duct and intestine of rats were surgically cannulated, and bile-pancreatic fluid was collected 2 h/d from the day of surgery to 8 d after surgery. The rats were fed diets containing 10, 100 or 1000 micrograms Zn/g diet before and after surgery. The effect of surgery itself was significant; food intake was initially lower than presurgery levels, but returned to presurgery levels by d 5. Protein and zinc concentrations, and carboxypeptidase A (CpA) and carboxypeptidase B (CpB) activities in bile-pancreatic fluid increased after surgery and leveled off at approximately d 6. Among the dietary zinc groups, the concentration of zinc in bile-pancreatic fluid varied significantly, whereas concentrations of calcium and copper did not. Zinc concentration in bile-pancreatic fluid for d 1-8 postsurgery averaged 1.8, 3.2 and 4.4 micrograms Zn/g, in the groups fed 10, 100 and 1000 micrograms Zn/g diet, respectively. Because the percent of zinc ingested that was secreted in bile-pancreatic fluid, estimated to be 57, 9.5 and 1.2% for the groups consuming the diets containing 10, 100 and 1000 micrograms Zn/g diet respectively, was not similar in the three groups, the quantity of zinc in bile-pancreatic fluid is not proportionally related to the amount of zinc ingested. Our results therefore suggest that zinc secretion in bile-pancreatic fluid does not play a major role in zinc homeostasis. Molecular localization of zinc in bile-pancreatic fluid and measurement of activity of CpA and CpB indicated that zinc in bile-pancreatic fluid is associated primarily with these digestive enzymes.
D000818:Animals; D001646:Bile / Q000378:metabolism*; D043424:Carboxypeptidase B; D002268:Carboxypeptidases / Q000378:metabolism; D043422:Carboxypeptidases A; D002850:Chromatography, Gel; D004032:Diet; D006706:Homeostasis; D007408:Intestinal Absorption; D008297:Male; D010189:Pancreatic Juice / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013514:Surgical Procedures, Operative; D015032:Zinc / Q000008:administration & dosage* / Q000378:metabolism
D002268:Carboxypeptidases; D043422:Carboxypeptidases A; D043424:Carboxypeptidase B; D015032:Zinc