Effects of ethanol and hemolysis on in vivo and in vitro platelet aggregation.

In vivo and in vitro platelet function were measured in male rats after intravenous injection of ethanol or water. There was a dose-related ethanol suppression of platelet aggregation induced by extravasation. Increased volumes of preformed microaggregates were seen in samples taken directly from the vena cava after injection of ethanol in doses that caused hemolysis. Lower doses of ethanol produced no demonstrable microaggregates or hemolysis: however, extravasation-induced aggregation was inhibited. Hemolysis was noted after intravenous injection of water, which also reduced the total volume and mean aggregate size of platelet aggregates induced by extravasation. Blood drawn from the inferior vena cava after induction of hemolysis had an increased volume of microaggregates, regardless of the agent producing hemolysis. In vitro studies revealed changes in spontaneous and ADP-induced aggregation only at very high concentrations of ethanol (greater than 3,000 mg/dl) and no effects at ethanol levels that altered in vivo aggregation. Ethanol, in doses that do not hemolyze erythrocytes, decreases platelet aggregation.