Previously, we showed that cadmium stimulates the production of glycosaminoglycans (GAGs) but inhibits their sulfation in cultured bovine aortic endothelial cells. The effect of zinc on such alterations of GAGs induced by cadmium was investigated in the present study. The incorporation of [3H]glucosamine and [35S]sulfate into GAGs was determined by the cetylpyridinium chloride precipitation method as a marker of GAG production and GAG sulfation, respectively. The incorporation of both [3H]glucosamine and [35S]sulfate was not changed in GAGs accumulated in the endothelial cell layer and the conditioned medium after exposure to zinc at 20 micrometers or less alone. A simultaneous exposure of the endothelial cell layer to zinc at 20 micrometers or less and cadmium at 2 micrometers resulted in prevention of the cadmium-induced decrease in [35S]sulfate incorporation; however, the cadmium-induced increase in [3H]glucosamine incorporation was not affected by zinc. Characterization of GAGs in the cell layer revealed that such an interaction between zinc and cadmium occurred in both heparan sulfate and the other GAGs. Zinc significantly prevented the inhibition of either [3H]thymidine or [3H]leucine incorporation caused by cadmium with less accumulation of intracellular cadmium suggesting that zinc decreased intracellular cadmium and protected endothelial cells from cadmium-induced inhibition of DNA and protein synthesis. The present data showed that a simultaneous exposure to cadmium and zinc resulted in an increase in heparan sulfate without a reduction of sulfation in the endothelial cell layer. The alteration may potentiate the antihrombogenic property of vascular endothelium.