DISTRIBUTION AND EXCHANGE OF ZINC IN DIFF ERENT TISSUE FRACTIONS AT DEFICIENT AND EXCESSIVE ZINC SUPPLY .3. EFFECT OF DIFFERENT ZINC SUPPLYON QUANTITATIVE ZINC EXCHANGE IN THE METABOLISM OF ADULT-RATS

Using the alimentary Zn-65 labelling technique the whole-body Zn of 32 growing female Sprague-Dawley rats was labelled for 28 days. Subseque ntly 5 of the now adult animals were killed for reference. The remaini ng 3 x 9 animals were restrictively fed a Zn-65-free diet. The Zn cont ent was either unchanged (24 ppm, control) or modified to 3 ppm (Zn de ficit) and 104 ppm (Zn excess). At day 17, 24 und 31 after the change in Zn supply 3 animals of each treatment group were killed and dissect ed into organs and tissue fractions. The amount and concentration of Z n in digestive organs, blood plasma, coat and skeleton was reduced by Zn depletion but not affected by high Zn supply. In liver, spleen, bra in, lung, reproductive organs, blood cells as well as muscle and fat t issue no changes were observed. The respective values in the kidneys w ere increased both by deficient and excessive Zn supply. Zn-deficient animals mobilised Zn from body stores, mainly from the skeleton. Allov er, the Zn-65 activity decreased with increasing Zn supply, indicating that Zn exchange was present in all tissue fractions. Only in the ske leton of Zn depleted animals was reduced Zn-65 activity observed due t o the mobilization of Zn stores.