title: Diurnal variation in melatonin effect on adenosine triphosphate and serotonin release by human platelets.
abstract: The effect of the pineal hormone melatonin on adenosine diphosphate-induced human platelet aggregation and adenosine triphosphate release was assessed in platelet-rich plasma obtained from normal volunteers at 08.30 and 20.30 h. In 10(-7)-10(-5) mol/l concentrations melatonin inhibited ADP-induced platelet aggregation only in the evening (p less than 0.05). ADP-induced ATP release, an index of platelet secretory processes, showed a generally greater, dose-dependent inhibition after adding melatonin (10(-9)-10(-5)mol/l) at 20.30 h as compared with 08.30 h. The inhibitory activity of melatonin (10(-9)-10(-5) mol/l) on [3H]serotonin release elicited by thrombin in washed human platelets obtained from normal volunteers was dose-dependent; the effect was generally greater at 20.30 h. The activity of the potent platelet anti-aggregating agent prostacyclin did not exhibit diurnal differences with respect to impairing ADP-induced platelet-rich plasma aggregation. These results indicate the existence of a diurnal variation of sensitivity to melatonin in human platelets.
authors.affiliation: Departamento de Fisiología, Faculta de Medicina, Hospital de Clínicas José de San Martín, Universidad de Buenos Aires, Argentina.
authors.forename: M M
authors.initials: MM
authors.lastname: Del Zar
authors.forename: M
authors.initials: M
authors.lastname: Martinuzzo
authors.forename: D P
authors.initials: DP
authors.lastname: Cardinali
authors.forename: L O
authors.initials: LO
authors.lastname: Carreras
authors.forename: M I
authors.initials: MI
authors.lastname: Vacas
mesh_terms: D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000097:blood*; D000328:Adult; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D008875:Middle Aged; D010974:Platelet Aggregation / Q000187:drug effects; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D012701:Serotonin / Q000097:blood*; D013917:Thrombin / Q000494:pharmacology
chemical_list: D010975:Platelet Aggregation Inhibitors; D012701:Serotonin; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D013917:Thrombin; D008550:Melatonin