BIOLOGICAL HALF-LIVES OF ZINC AND MANGANESE IN RAT-BRAIN

The brains of rats injected intravenously with (ZnCl2)-Zn-65 or (MnCl2 )-Mn-54 were subjected to high-resolution autoradiography. The distrib ution of Zn-65 and Mn-54 in each brain region gradually decreased from 6 days to 42 days for Zn-65 and from 15 days to 60 days for Mn-54 aft er the injection. The biological half-lives of Zn in each region studi ed were in the range of 16-43 days; the longest was observed in the am ygdaloid nuclei. The regions where the long biological half-life was o bserved were consistent with the ones with the high density of Zn-cont aining neuron terminals reported previously. The biological half-lives of Mn in each region determined were 51-74 days; the longest were tho se in the hypothalamic nuclei and thalamus.