Variectomy eliminates sex differences in rat tail artery response
to adrenergic nerve stimulation.
Li, Zhen, Diana N. Krause, Suzanne Doolen, and Sue Piper Duckles.
Department of Pharmacology, College of Medicine, University of
California, Irvine, CA 92697-4625
APStracts 3:0531H, 1996.
The influence of gonadal hormones on vasoconstrictor responses to
adrenergic nerve stimulation was investigated by comparing tail
arteries from intact and gonadectomized male and female Fisher 344
rats. Arterial ring segments from females were significantly less
responsive to transmural nerve stimulation (1 - 8 Hz) than arteries
from age-matched males. Significant male-female differences persisted
after correcting the contractile responses for sex-related
differences in arterial mass, optimal resting tension and maximal
contractile force. Arteries were taken from cycling, intact females
in either proestrus, estrus, metestrus or diestrus; but no
significant differences were found among the four stages for
vasoconstrictor responses to either adrenergic nerve stimulation or
exogenous norepinephrine. These data suggest adrenergic function in
the artery is not affected by hormonal variations during the estrous
cycle. Following bilateral ovariectomy, however, contractile
responses of female arteries to adrenergic nerve stimulation were
increased to levels similar to those observed in male arteries.
Orchidectomy of males, in contrast, had no effect on neural-evoked
contraction. Low concentrations of norepinephrine also produced
greater contractile responses in male as compared to female arteries;
however this sex-related difference was eliminated by orchidectomy
but not ovariectomy. Taken together, the results indicate that
circulating gonadal hormones contribute to gender differences
observed in rat tail artery. Vasoconstrictor responses to exogenous
norepinephrine appear to be enhanced by testicular hormones. In
contrast, vasoconstriction induced by adrenergic nerve stimulation
appears to be influenced by chronic exposure to circulating ovarian
hormones, resulting in a smaller vascular response in female
arteries.
Received 24 March 1996; accepted in final form 3 November 1996.
APS Manuscript Number H279-6.
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