Zinc-induced tolerance to cadmium cytotoxicity without metallothionein induction in cultured bovine aortic endothelial cells.

We investigated the cytotoxicity of cadmium in cultured vascular endothelial cells from bovine aorta pretreated with zinc. The cytotoxicity was evaluated by the [3H]adenine release assay. It was shown that the increase in the [3H]adenine release after challenge with cadmium was significantly prevented by pretreatment with zinc. It was histologically observed that cadmium-induced occurrence of the de-endothelialized areas was reduced in zinc-pretreated cell layer. Intracellular accumulation of cadmium was significantly less but that of zinc was more in zinc-pretreated cells. The content of cadmium in both the particulate and the cytosol fraction was decreased by zinc pretreatment; however, metallothionein content after challenge with cadmium was not changed. It was therefore concluded that zinc is capable of inducing a tolerance to cadmium cytotoxicity in cultured vascular endothelial cells; this tolerance is postulated to be due to a decrease in the intracellular cadmium accumulation rather than a metallothionein induction.