EFFECT OF PHOSPHATE ON THE ABSORPTION AND RETENTION OF LEAD IN THE RAT

An inverse relationship between Pb retention and dietary phosphate content is known but the reasons for this association remain unknown. In rats, the manipulation of dietary phosphate content had no significant effect on the absorption of Pb from isolated gastrointestinal segments, but animals fed low phosphate content food had increased whole-body retention and bone deposition of i.v. administered tracer doses of radiolead. Intraluminal phosphate decreased the absorption of test doses of radiolead from the small intestine, possibly due to precipitation of Pb in the gut lumen. Rats fed low phosphate diets absorbed increased quantities of an oral Pb dose. Dietary phosphate deficiency may significantly increase body Pb burdens by decreasing intraluminal Pb precipitation and increasing Pb retention, primariy in bone. Increased dietary phosphate acted primarily to limit Pb absorption.