STUDIES OF HUMAN ZINC KINETICS USING THE STABLE ISOTOPE ZN-70

1. The short-term (120 min) kinetics of Zn turnover has been studied in control subjects and patients with alcoholic liver disease after intravenous injection of 0.5 mg of 96.5% enriched (ZnCl2)-Zn-70. 2. The Zn-70 enrichment of plasma was found closely to obey two-compartment kinetics and the derived two-component decay equation has been used to calculate the size and turnover of the initial two rapidly exchanging pools of body Zn. 3. In normal subjects isotopic Zn appears initially to equilibrate with the whole of the plasma Zn which comprises the first metabolic compartment, pool a. This has a size of 0.72 +/- 0.1 mumol/kg. Zn-70 equilibration then occurs with a second compartment, pool b, consistent with a rapidly exchanging liver Zn pool of size 3.60 +/- 0.93 mumol/kg. The fractional turnover rate of pool b was found to be fivefold slower than that of pool a. 4. In the alcoholic group an expansion of pool a was observed (1.63 +/- 0.39 mumol/kg), but the size of the second pool was not significantly different from that of control subjects (5.55 +/- 1.0 mumol/kg), although its fractional turnover was significantly increased (K(ab): control subjects, 0.018 +/- 0.002 min-1, alcoholic patients, 0.031 +/- 0.006 min-1). 5. These data therefore demonstrate that kinetic studies using stable isotopes of Zn can provide novel information on exchangeable Zn pools in man, but provide no support for the possibility of an underlying Zn depletion in patients with alcoholic liver disease.