Vascular effects of 17 beta-estradiol in male Sprague-Dawley rats.
Bolus intravenous injections of 100 micrograms/kg 17 beta-estradiol significantly decreased the pressor responses to norepinephrine (NE; 0.3 microgram/kg) at the fourth, fifth, and sixth hour in anesthetized male Sprague-Dawley rats. At doses of 10(-6) to 3 x 10(-5) M, 17 beta-estradiol relaxed the sustained phase of contraction in male Sprague-Dawley rat tail artery helical strips precontracted in vitro by [Arg8]vasopressin (AVP), KCl, or NE. The effect was dose dependent. At doses of 3 x 10(-6) to 3 x 10(-5) M, it also decreased the initial phase of tension generation and extracellular Ca(2+)-dependent vasoconstriction induced by NE, AVP, or KCl in a dose-dependent manner in male Sprague-Dawley rat tail artery helical strips. 17 beta-Estradiol (2 x 10(-8) to 2 x 10(-6) M) decreased the voltage-dependent inward Ca2+ current and the intracellular free Ca2+ concentration ([Ca2+]i) increment induced by 15 mM KCl in a dose-dependent manner (3.6 x 10(-8) to 3.6 x 10(-6) M) in vascular smooth muscle cells (VSMC) isolated from male Sprague-Dawley rat tail arteries. We suggest that, at pharmacological doses, estrogen has a direct vasodilating effect on the rat tail artery that is mediated by its inhibitory effect on Ca2+ influx through voltage-dependent Ca2+ channels. The inhibitory effect of estrogen on the pressor responses to NE or AVP may be correlated with its modulation of VSMC [Ca2+]i through its actions on membrane Ca2+ channels.
Shan
J
J
Department of Physiology, University of Alberta, Edmonton, Canada.
Resnick
L M
LM
Liu
Q Y
QY
Wu
X C
XC
Barbagallo
M
M
Pang
P K
PK
D000818:Animals; D001127:Arginine Vasopressin / Q000494:pharmacology; D001158:Arteries; D001794:Blood Pressure / Q000187:drug effects; D001808:Blood Vessels / Q000187:drug effects*; D002118:Calcium / Q000502:physiology; D002122:Calcium Chloride / Q000378:metabolism; D004553:Electric Conductivity; D004958:Estradiol / Q000494:pharmacology*; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D013623:Tail / Q000098:blood supply; D014661:Vasoconstriction / Q000187:drug effects
D001127:Arginine Vasopressin; D004958:Estradiol; D011189:Potassium Chloride; D002122:Calcium Chloride; D002118:Calcium; D009638:Norepinephrine