help button home button Endocrine Society JCEM JCEM Call for Nominations for EIC
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
This Article
Right arrow Submit a related Letter to the Editor
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow Request Copyright Permission
Citing Articles
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Del Zar, M. M.
Right arrow Articles by Vacas, M. I.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Del Zar, M. M.
Right arrow Articles by Vacas, M. I.

Journal of Clinical Endocrinology & Metabolism, Vol 70, 246-251, Copyright © 1990 by Endocrine Society

ARTICLES

Inhibition of human platelet aggregation and thromboxane-B2 production by melatonin: evidence for a diurnal variation

MM Del Zar, M Martinuzzo, C Falcon, DP Cardinali, LO Carreras and MI Vacas
Departamento de Fisiologia, Facultad de Medicina, Universidad de Buenos Aires, Argentina.

The effects of melatonin on platelet aggregation and thromboxane-B2 (TxB2) production induced by 1-4 x 10(-6) M adenosine diphosphate (ADP) or 0.6 x 10(-3) M arachidonic acid (AA) were assessed in platelet-rich plasma (PRP). Micromolar concentrations of melatonin inhibited in a dose-dependent way ADP-induced platelet aggregation with individual inhibitions 40% or more at 10(-6)-10(-5) M. A significant depression of AA-induced platelet aggregation was observed only at 10(-5)-10(-4) M melatonin. Morning (0830 h)-evening (1800 h) studies of ADP-induced platelet aggregation in seven normal men showed a higher sensitivity at 1800 h when analyzed as a global inhibitory effect of melatonin (P less than 0.01). Moreover, only during the evening hours did melatonin induce reversible aggregation, an index of inhibition of the platelet secretory process elicited by ADP exposure. No diurnal variability in melatonin inhibition of AA-induced aggregation was detected. TxB2 production elicited by AA in the evening was inhibited significantly in a concentration-related manner by a 2-min preincubation with 10(-9)-10(- 5) M melatonin, while during the morning hours the inhibition was significant only at 10(-6) M or higher melatonin concentrations. In the case of ADP, the inhibition of TxB2 release attained significance at 10(-5)-M (0830 h) or 10(-6)-M concentrations (1800 h). In the presence of either stimulatory agent, melatonin depression of TxB2 generation was about 2-fold greater at 1800 h than at 0830 h. The diurnal changes in melatonin effect on TxB2 production were also observed in thrombin- stimulated washed platelets. The present data indicate the existence of circadian variations in platelet responsiveness to melatonin in humans.




HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
Endocrinology Endocrine Reviews J. Clin. End. & Metab.
Molecular Endocrinology Recent Prog. Horm. Res. All Endocrine Journals
Copyright © 1990 by The Endocrine Society