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This Article Full Text Full Text (PDF) All Versions of this Article: 286/2/H552    most recent 00663.2003v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (15) Citing Articles via Google Scholar Google Scholar Articles by Gonzales, R. J. Articles by Duckles, S. P. Search for Related Content PubMed PubMed Citation Articles by Gonzales, R. J. Articles by Duckles, S. P.

Testosterone suppresses endothelium-dependent dilation of rat middle cerebral arteries

Department of Pharmacology, College of Medicine, University of California, Irvine, Irvine, California 92697-4625

Submitted 11 July 2003 ; accepted in final form 5 October 2003

Little is known about vascular effects of testosterone. We previously reported chronic testosterone treatment increases vascular tone in middle cerebral arteries (MCA; 300 µm diameter) of male rats. In the present study, we investigated the hypothesis that physiological levels of circulating testosterone affect endothelial factors that modulate cerebrovascular reactivity. Small branches of MCA (150 µm diameter) were isolated from orchiectomized (ORX) and testosterone-treated (ORX+T) rats. Intraluminal diameters were recorded after step changes in intraluminal pressure (20–100 Torr) in the absence or presence of N^G-nitro-L-arginine-methyl ester (L-NAME), a nitric oxide synthase (NOS) inhibitor; indomethacin, a cyclooxygenase (COX) inhibitor; and/or apamin and charybdotoxin (CTX); and K_Ca channel blockers used to inhibit endothelium-derived hyperpolarizing factors (EDHF). At intraluminal pressures 60 Torr, arteries from ORX+T developed greater tone compared with ORX arteries. This difference was abolished by removal of the endothelium but remained after treatment of intact arteries with indomethacin or L-NAME. In addition, testosterone treatment had no effect on cerebrovascular production of endothelin-1 or prostacyclin nor did it alter protein levels of endothelial NOS or COX-1. Endothelium removal after L-NAME/indomethacin exposure caused an additional increase in tone. Interestingly, the latter effect was smaller in arteries from ORX+T, suggesting testosterone affects endothelial vasodilators that are independent of NOS and COX. Apamin/CTX, in the presence of L-NAME/indomethacin, abolished the difference in tone between ORX and ORX+T and resulted in vessel diameters similar to those of endothelium-denuded preparations. In conclusion, testosterone may modulate vascular tone in cerebral arteries by suppressing EDHF.

endothelium; vascular tone; endothelium-derived hyperpolarizing factor

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