PLATELET-AGGREGATION AND ATRIAL-NATRIURETIC-PEPTIDE

1. Isolated human platelets were used to investigate the effect of atr ial natriuretic peptide (ANP) on in vitro platelet aggregation induced by epinephrine, ADP, collagen and 5-hydroxytryptamine. As a direct st imulant of particulate guanylate cyclase, ANP is known to have no dire ct effect on platelets which contain soluble guanylate cyclase. 2. In our experiments ANP inhibited epinephrine- and partially ADP-induced a ggregation in vitro and this effect was suggested to be the result of an interaction of the peptide with adenylate cyclase in platelets. How ever, the concentrations required to produce this effect were higher t han those expected to be found in the circulation both physiologically and pathologically. 3. We therefore conclude that though the peptide may inhibit aggregation via adenylate cyclase activation, it is unlike ly that ANP may play a direct role in preventing platelets aggregating .