The effect of methylmercuric chloride on arachidonic acid metabolism by platelet lipoxygenase.

It has been reported that the addition of nonaggregating concentrations of collagen, epinephrine, thrombin or arachidonic acid to platelets potentiate their responses to subsequent subthreshold concentrations of aggregating agents. We have previously reported that low concentrations of methylmercury will potentiate human platelet ATP secretion and that this effect is blocked by aspirin. Using rat platelets we have examined the effect of low concentrations of methylmercury on the metabolism of arachidonic acid. Low concentrations of methylmercury (20-100 microM) inhibit washed platelet lipoxygenase activity. In experiments using platelet rich plasma a higher concentration of methylmercury was required to produce a comparable inhibition of arachidonic acid metabolism. At these concentrations no inhibition of platelet thromboxane synthetase was seen. These findings suggest that methylmercury potentiates platelet aggregation and secretion by reducing the inhibitory effect of 12 HPETE on thromboxane biosynthesis.