Effects of methanol and formic acid on human platelet aggregation

BACKGROUND: Although ethanol is known to inhibit platelet aggregation, the effects of another variant of alcohol, methanol, have not been reported. The purpose of this study was to determine whether methanol and its metabolite, formic acid, affect Ca(2+) entry into and subsequent aggregation of platelets in vitro. METHODS: Ca(2+) entry into and aggregation of human platelets were measured by spectrofluorometry using Fura-2/AM as an indicator and the light transmission method, respectively. RESULTS: Thrombin-induced platelet aggregation was significantly augmented by methanol at pharmacological concentrations (0.5–2%) in a concentration-dependent manner. Methanol at 2% significantly attenuated thapsigargin-induced platelet aggregation, which was not significantly affected by lower concentrations (0.5 and 1%) of methanol. Methanol (0.5–2%) did not significantly affect platelet aggregation induced by 1-oleoyl-2-acetyl-sn-glycerol (OAG), or Ca(2+) entry into platelets induced by thrombin, thapsigargin, or OAG. Platelet aggregation induced by thrombin, thapsigargin, or OAG was significantly inhibited by formic acid at toxic concentrations (0.01% or higher). Ca(2+) entry into platelets induced by thrombin or thapsigargin was also significantly inhibited by formic acid at 0.01% or higher, while that induced by OAG was not affected by formic acid at 0.005 and 0.01% and augmented by that at 0.02%. CONCLUSIONS: Methanol at pharmacological doses has diverse effects on platelet aggregation, depending on the aggregation stimuli, without affecting Ca(2+) entry into platelets. Formic acid at toxic concentrations has an inhibitory action on platelets aggregation, which was partly explained by the reduction of Ca(2+) entry into platelets.