DISTRIBUTION AND EXCHANGE OF ZN IN TISSUE S OF ZN-65-LABELED RATS .2.STUDIES OF THE QUANTITATIVE ZN EXCHANGE IN THE METABOLISM OF ADULT-RATS AT PHYSIOLOGICALLY ADEQUATE ZN SUPPLIES

A total of 32 female Sprague Dawley rats (50 g initial body weight) we re reared for 9 weeks with a semisynthetic diet containing 23 ppm Zn a nd 8.5 Bq Zn-65/mu g Zn. Subsequently, five of the now adult animals w ere killed for reference. The remaining animals were divided into nine groups (n=3) and were restrictively fed a Zn-65-free diet containing 19, 23, 29, 37, 46, 58, 73, 92 or 114 ppm Zn. After 23 days, the anima ls were killed and dissected completely into different tissue fraction s. The different Zn supply did not affect the quantities and concentra tions of zinc in the tissues and the whole body. The whole-body zinc ( 6850 mu g) was distributed as follows: 7% in the organs, 34% in the mu scle and fat tissues, 40% in the skeleton, 18% in the coat (skin and h air), and less than 1% in the blood. An increase in Zn exchange with r ising Zn supply was observed in all tissue fractions. The exchangable proportion of tissue zinc was as follows: about 100% in liver, spleen, lung, digestive tract, blood cells, and blood plasma, about 75% in br ain and kidneys, 71% in the total muscle and fat tissue, 27% in the co at, and 23% in the skeleton. The whole-body zinc was exchangable at 45 %.