Metabolism of zinc-65

Abstract

The absorption, deposition, and excretion of zinc⁶⁵ was studied in mice, rats, and dogs. When zinc⁶⁵ was fed to the animals it was poorly absorbed, but its long biologic half-life made even the small portion absorbed physiologically significant. Absorption was obviated by feeding large quantities of nonradioactive carrier zinc. Injected zinc⁶⁵ chloride first was deposited, preferably in the pancreas, liver, and spleen, with only minor deposition in muscle and in the brain. Subsequently, a large proportion was transferred to bone. The chief means of excretion was in feces, presumably via pancreatic secretion. Injected nonradioactive zinc or treatment with 2,3-dimercaptopropanol (BAL), Versene, or cadmium ion failed to alter body burden significantly. Cadmium, however, decreased soft tissue zinc⁶⁵ deposition and increased accretion by the skeleton. Blood activity fell rapidly and less than .01% of the dose injected remained in the blood after 1 day. Renal excretion of zinc⁶⁵ rose as plasma concentration fell and clearance ratios in excess of 1.0 were noted, indicating probable renal secretion.