ZINC EXCRETION AND THE KINETICS OF ZINC E XCHANGE IN THE WHOLE-BODY ZINC AT DEFICIENT AND EXCESSIVE ZINC SUPPLY .2. EFFECT OF DIFFERENT ZINC SUPPLY ON QUANTITATIVE ZINC EXCHANGE IN THE METABOLISM OF ADULT-RATS

32 growing female Sprague-Dawley rats were subjected to an alimentary Zn-65-labelling procedure for 28 days. Subsequently 5 of the now adult rats were killed for reference. The remaining animals were restrictiv ely fed a Zn-65-free diet with either unchanged Zn content (24 ppm, co ntrol), or 3 ppm Zn (deficit), and 104 ppm Zn (excess), respectively. From 4 days before, until 31 days after the change in Zn supply, the f aecal and urinary excretions were collected. Deficient Zn supply reduc ed faecal and renal excretion of both Zn and Zn-65. The adjustment to the new excretion level was reached within 4 days (faeces) and 1 day ( urine) after the change in dietary Zn content. Excessive Zn supply res ulted in an oscillating increase in faecal Zn and Zn-65 excretion whic h stabilized after one week. At the same time, the renal Zn excretion increased, while the renal Zn-65-excretion fell below the control leve l. At the end of the experiment the total excretion of Zn-65 was 10 % (deficit), 30 % (control) and 39 % (excess) of initial whole-body acti vity. The whole-body level of Zn was exchangeable at 15 % (deficit), 4 8 % (control) and 49 % (excess) with half lives of 26, 23 and 15 days.