© 2000 by European Society of Cardiology
Copyright © 2000, European Society of Cardiology
Acute impairment of relaxation by low levels of testosterone in porcine coronary arteries
Department of Pharmacology, Faculty of Medicine, The University of Hong Kong, 1/F Li Shu Fan Building, 5 Sassoon Road, Hong Kong SAR, Hong Kong
* Corresponding author. Tel.: +852-2819-9850; fax: +852-2817-0852 rykman{at}hkucc.hku.hk
Objectives: While there are many suggested reasons for the marked gender bias in cardiovascular events, much of the available data indicate that circulating estrogens are cardioprotective. The possibility that endogenous androgens may be detrimental to the cardiovascular system has received relatively less attention. We investigated the short-term modulatory effects of various concentrations of testosterone on vascular function in isolated porcine coronary artery rings. Results: The higher concentrations (>1 µM) of testosterone relaxed U46619 [GenBank] -contracted coronary artery rings in an endothelium-independent manner. This direct effect was insensitive to the testosterone receptor antagonists, flutamide and cyproterone acetate. Short-term exposure (20 min) to low levels of testosterone (1–100 nM), which were ineffective on their own on vascular function, significantly diminished relaxation to bradykinin and calcium ionophore A23187 [GenBank] but not those produced by levcromakalim and sodium nitroprusside. The inhibitory effect observed with 1 nM testosterone was only partially reversed by flutamide and cyproterone acetate and unaltered in the presence of actinomycin D and cycloheximide. Conclusions: These results demonstrate that acute treatment with testosterone, at concentrations that have no effect on their own, reduces vasorelaxation. Furthermore, they suggest that this modulatory action may be in part independent of the classical testosterone receptor since it was not completely sensitive to the anti-androgens and was not inhibited by the transcriptional and translational inhibitors. These findings support the postulation that testosterone may have unfavorable influences on vascular function.
KEYWORDS Hormones; Receptors; Arteries; Vasodilation; Coronary circulation
1 Current address: Terrence Donnelly Heart Centre, St. Michael's Hospital, 30 Bond Street, Toronto, Ontario M5B 1W8, Canada.
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