Effects of alcohols on ADP-induced aggregation and membrane fluidity of gel-filtered bovine blood platelets.

The effects of four alcohols--n-propyl, n-butyl, n-amyl and n-hexyl alcohol--on the ADP-induced aggregation of gel-filtered bovine platelets were examined. All four alcohols inhibited the aggregation, the order of their effects being n-propyl less than n-butyl less than n-amyl less than n-hexyl. Comparison of the inhibitory effects of the alcohols with their physico-chemical properties showed that their degrees of inhibition depended on their hydrophobicities. Moreover, it was suggested that their interaction with the lipid layer of the membrane was important for the inhibition. Studies on the effects of alcohols on the fluorescence polarization of 1,6-diphenyl-1,3,5-hexatriene-labeled platelets showed that the membrane fluidity of the platelets increased in the same concentration range in which aggregation inhibition was observed. Since the alcohols inhibited aggregation without affecting Ca2+ mobilization in the platelets, as revealed in this study, it was concluded that inhibition of platelet aggregation was due to perturbation of membrane lipids by the alcohols. This hypothesis is supported by several recent studies on the effects of cholesterol and cations, which suggest that a relatively rigid membrane favors platelet aggregation.