Effects of riboflavin-2', 3', 4', 5'-tetrabutyrate on platelet function and plasma lipids

Riboflavin-2', 3', 4', 5'-tetrabutyrate (B2-But) inhibited, in vitro, ADP (4 micrograms/ml)-induced platelet aggregation when added at the concentration of more than 1 microgram/ml and arachidonic acid (Aa) (1 mM)-induced platelet aggregation when given at the concentration of more than 0.1 microgram/ml. These inhibitions were dose-dependent. Both cyclic AMP and prostaglandin metabolites in the platelets, however, remained unchanged when the amount of B2-But added was between 0.1-10 micrograms/ml. In a volunteer study, 80 mg of B2-But taken in one bolus inhibited both ADP- and Aa-induced platelet aggregation 4 hr after oral administration. The administration of B2-But at this dose was associated with a significant decrease in malondialdehyde formation in plasma. The oral administration of 40 mg (t.i.d.) of B2-But daily did not result in significant changes in ADP- and Aa-induced platelet aggregation. B2-But showed no significant effects on either platelet adhesiveness or collagen-induced platelet aggregation, in vitro or in vivo. Our data suggest that a decrease of lipoperoxide in plasma, not in platelets, influences platelet aggregation induced by ADP and Aa.