The relation between the 5-hydroxytryptamine content and aggregation of rabbit platelets.
1. Blood platelets containing different amounts of 5-hydroxytryptamine (5-HT) were produced in vivo by the injection of 5-hydroxytryptamine or of reserpine into normal rabbits and of 5-hydroxytryptamine into reserpinized rabbits. Before and after these injections the aggregation of platelets was measured in vitro.2. Platelets of untreated rabbits were aggregated by adenosine diphosphate (ADP) and by 5-hydroxytryptamine; (-)-adrenaline alone did not produce aggregation but markedly increased aggregation by 5-hydroxytryptamine.3. Platelets saturated with 5-hydroxytryptamine in vivo were no longer aggregated in vitro by 5-hydroxytryptamine or by 5-hydroxytryptamine plus adrenaline, but their aggregation by ADP was unchanged.4. Platelets from reserpinized rabbits lost about 99% of their 5-hydroxytryptamine; the aggregation of these platelets did not differ significantly from that of platelets from control rabbits.5. Platelets from reserpinized rabbits injected with 5-hydroxytryptamine were aggregated neither by the amine alone nor by 5-hydroxytryptamine plus adrenaline, although these platelets contained much less 5-hydroxytryptamine than saturated platelets and only about one tenth as much as platelets from untreated rabbits.6. The findings support the hypothesis that the inhibitory effect of 5-hydroxytryptamine administered in vivo on platelet aggregation in vitro is due to the association of the amine with the platelet membrane.
D000227:Adenine Nucleotides / Q000494:pharmacology; D000818:Animals; D001777:Blood Coagulation; D001792:Blood Platelets / Q000032:analysis*; D004357:Drug Synergism; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D066298:In Vitro Techniques; D007275:Injections, Intravenous; D008297:Male; D011817:Rabbits; D012110:Reserpine / Q000494:pharmacology; D012701:Serotonin / Q000032:analysis* / Q000494:pharmacology
D000227:Adenine Nucleotides; D012701:Serotonin; D012110:Reserpine; D004837:Epinephrine