An autoradiographic study on the fate of 65Zn in zinc-rich tissues in some rodents.

Whole-body autoradiography of 65Zn, administered as 65ZnCl2, in mice showed a high initial radioactivity in several parenchymatous organs. Some other tissues showed a rather slow accumulation and a pronounced retention of 65Zn. This applied to the pancreatic islets, which showed the highest soft-tissue radioactivity at most survival intervals and in which 65Zn was detected still 60 days after a single dose. 65Zn was also retained in the hippocampus of the brain, the dorsolateral prostate, Paneth cells in the intestine, the bone and the hair. A few guinea-pigs and rabbits were studied. In the guinea-pigs, there was no specific labelling of the pancreatic islets. The rabbits showed the highest soft-tissue radioactivity in the mandibular salivary gland. Most tissues which retained a high level of 65 Zn have previously been reported as containing high levels of endogenous zinc. The results of the present study indicate that there is a slow zinc-turnover in these tissues.