Because zinc attenuates endothelial cell dysfunction that proceeds atherosclerosis, depressed zinc status may be involved in the initiation of endothelial dysfunction. However, before recommending a zinc-enriched diet to reduce the risks for atherosclerosis, the effect of excess zinc on endothelial cell functions in normozincemic status should be known. Therefore, in this study, the effect of dietary zinc on normal endothelial cell functions in animals subjected to a diet containing 334 +/- 58 ppm zinc for 30 d was studied to see whether supplemented zinc has an effect on endothelial cells. Despite a slight increase in blood zinc, unaltered aortic and kidney zinc contents were associated with unchanged blood pressure in rats subjected to a zinc-enriched diet. Increased basal nitric oxide and prostacyclin were accompanied by a normal response to phenylephrine. Dietary zinc influenced neither endothelial-dependent nor endothelial-independent relaxations significantly. However, it elevated the share of M1-type cholinoceptor response as well as dilator prostaglandin release, which seems to be nitric oxide dependent. There was a strong correlation (r = 0.826, p < 0.05) between M1-type cholinoceptor response and prostacyclin release in zinc-treated rings. These results suggested that zinc ions increases M1-mediated prostacyclin release in normal endothelial cells without altering intracellular pathways.