Gender difference in myogenic tone of rat arterioles is due to
estrogen-induced, enhanced release of nitric oxide.
Huang, An, Dong Sun, Akos Koller, and Gabor Kaley.
Department of Physiology, New York Medical College, Valhalla, NY
10595
APStracts 3:0489H, 1996.
The characteristics of arteriolar myogenic responses of female rats
have not yet been investigated. Thus, experiments were conducted on
isolated gracilis muscle arterioles ( 55 _m in diameter) of four
groups of twelve week old rats: males, females, females
ovariectomized with no estrogen replacement (OV), and females
ovariectomized with estrogen replacement (OV+E2; 50 _g/kg, sc.
injection of 17[beta]-estradiol benzoate every 48 hours). Diameter
changes in response to increases in perfusion pressure from 20 to 140
mmHg and to various concentrations of substance P (SP, 10-9M-5x10-8M)
and sodium nitroprusside (SNP, 10-8M-10-6M) were measured before and
after administration of N_-nitro-L-arginine (L-NNA, 10-4M), an
inhibitor of nitric oxide synthase. Arteriolar diameters of males and
OV females were significantly less in the pressure range from 60 to
140 mmHg than those of normal females and OV+E2 females (at 80mmHg
45.4+/-1.8, 43.1+/-2.2 vs. 58.4+/-1.6, 57.3+/-1.3%). L-NNA elicited a
significantly greater downward shift of pressure-diameter curves in
arterioles of normal females and OV+E2 females than in those of males
and OV females (28.6+/-4.6, 30.6+/-4.7 vs. 13.2+/-0.9, 10.4+/-2.6%).
Dilations of arterioles from normal females and OV+E2 females to
substance P were significantly greater (by 50-60%) than those from
males and OV females (20.8+/-1.8, 22.3+/-1.9 vs. 13.8+/-1.4, 13.8+/
-0.6% at 10-8M). L-NNA did not affect dilations to SNP, but
significantly reduced the dilation of arterioles in all groups to SP,
more so in male and OV female arterioles than in those of the other
two groups. We conclude, that pressure-induced myogenic constriction
of arterioles of females is less pronounced than that of male rats
which is, most likely, due to the enhanced release and/or activity of
nitric oxide related to the presence of estrogen.
Received 29 April 1996; accepted in final form 6 November 1996.
APS Manuscript Number H376-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996