Skip Navigation

European Heart Journal 1992 13(4):550-555;
Copyright © 1992 by the European Society of Cardiology.
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
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 Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by WILLICH, S. N.
Right arrow Articles by COLUCCI, W. S.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by WILLICH, S. N.
Right arrow Articles by COLUCCI, W. S.
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

© 1992 The European Society of Cardiology

Platelet alpha2 adrenoceptor characteristics during the morning increase in platelet aggregability

S. N. WILLICH*,{ddagger},, G. H. TOFLER*, D. A. BREZINSKI{dagger}, A. I. SCHAFER{dagger}, J. E. MULLER*, T. MICHEL{dagger} and W. S. COLUCCI{dagger}

*Institute for Prevention of Cardiovascular Disease, Deaconess Hospital
{dagger}Brigham and Women's Hospital, Harvard Medical School Boston, U.S.A.
{ddagger}Klinikum Steglitz, Free University Berlin, Germany

Received 8 August 1991; accepted 8 August 1991.

Correspondence Dr Stefan N Willich. Department of Medicine, Klinkum Steglitz, Free University of Berlin, Hindenburgdamm 30. 1000 Berlin 45. Germany

Abstract

The incidence of myocardial infarction and sudden cardiac death increases in the morning, as do platelet aggregability and sympathetic activity. We considered the possibility that increased platelet aggregability in the morning was due to an increase in platelet alpha2 adrenergic receptor number or agonist binding affinity, or to a temporal disparity between the increase in sympathetic activity that accompanies arising and the anticipated decrease in platelet high affinity alpha2 adrenoceptors.

To evaluate these possibilities, we studied eight healthy male volunteers (20–35 years) before and 1–1.5 and 3–4 h after they arose at 08.00 h and performed routine morning activities. Platelet aggregability Has determined in platelet-rich plasma; alpha, adrenoceptor density and agonist binding affinity were determined in intact platelets and in membrane preparations using the alpha2 selective ligand [3H]-yohimbine.

The threshold concentration of epinephrine required to produce biphasic aggregation decreased (i.e. platelet aggregability increased) from 3.6 ± 1.2 to 0.9 ± 0.3 µM (P <0.05) after arising. However, alpha2 adrenoceptor density (380 ± 71 to 365 ± 51 sites per platelet) and agonist binding affinity assessed simultaneously did not change after arising, suggesting that the increase in platelet aggregability is due to factors extrinsic to the platelets or to an intra-platelet mechanism distal to the receptor level.

Key Words: Alpha2 adrenoceptor • platelet aggregation • circadian variation • myocardial infarction • sudden cardiac death


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.