Intestinal lead absorption in rats: effects of circadian rhythm, food, undernourishment, and drugs which alter gastric emptying and GI motility.

In rats, the absorption of a 10 mg/kg oral lead dose was reduced by the presence of food in the intestine. In vitro intestinal lead permeability was similar using intestines from fasted or fed rats. No circadian rhythm was apparent in lead absorption or transport across everted rat intestines in vitro. The effects of feeding and circadian rhythm on lead absorption are different from the effects on calcium absorption. Pretreatment of rats with propantheline (5 mg/kg, i.p.) delayed and decreased lead absorption, whereas metoclopramide (10 mg/kg, o.p.) had no significant effect. Lead absorption in undernourished rats, which were allowed only 20-25% of their normal food intake, was similar to control, but the distribution of systemically administered lead was altered.