Comparative metabolism of radionuclides in mammals. I. Uptake and retention of orally administered Zn65 by four mammalian species.

Abstract

Uptake and retention of a single oral administration of Zn65cl2 in mice, rats, dogs, and 4 human subjects were studied by whole-body counting methods. Retention functions for each species were accurately represented by multiple rate equations composed of three exponential terms. The average effective half time of the longest component (which accounts for approximately 95 per cent of all the disintegrations occurring in the body) of the retention curve for man was 154 days with a range of 149-I61 days. A parabolic relationship between species weight and equilibrium level for chronic exposure was derived and used to estimate Zn65 (MPC)w values for man. The average (MPC)w value (168 hr/week exposure) obtained directly from the human data by usual methods was 3.1 × 10-4 microc/ml with a range of 1.7–4.7 × 10-4 microc/ml compared with 2.4 × 10-4 microc/ml when derived from interspecies correlation data.