Zinc uptake by isolated rat hepatocytes.

Isolated rat hepatocytes were used to investigate the uptake of zinc of early exposure times. Hepatocytes were incubated with 65Zn (1--500 microM) and samples were withdrawn at times ranging from 25 s to 60 min. A biphasic pattern of uptake was observed with a rapid first phase of uptake followed by a slower second phase. The relationship between velocity of uptake and substrate concentration for the first phase was nonlinear, while that of the second phase was linear. The presence of 10 microM cadmium produced a decrease in the velocity of uptake of only the first phase. This suggests that the first phase is at least partly carrier mediated, while there is no indication of involvement of a carrier in the second phase. KCN (1 mM) and carbonyl cyanide m-chlorophenylhydrazone (2 microM), did not cause any change in the uptake of 65Zn (1 microM), which suggests that there is no active component in the uptake of zinc.