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-estradiol in absence of NO in
ovariectomized rats: role of angiotensin II
Departamento de Fisiología y Farmacología, Facultad de Medicina, Universidad de Murcia, Campus de Espinardo, 30100, Murcia, Spain
Previous reports correlate plasma levels of
estrogen with increased nitric oxide (NO) production. To investigate
whether the hemodynamic effects of estrogens are mediated by NO, we
compared the hemodynamic changes induced by 17
-estradiol (100 µg/kg) in the absence and presence of the NO synthesis inhibitor
N
-nitro-L-arginine methyl ester
(L-NAME). All protocols were
performed in ovariectomized, conscious rats. Estradiol alone resulted
in no significant changes in cardiac index (CI) or mean arterial pressure (MAP). However, in the presence of
L-NAME, estradiol induced a
significant increase in total peripheral resistance (TPR) of 37.3 ± 11.7% and a decrease in CI of 27 ± 4.9%, without changes in MAP.
Previous blockade of angiotensin II
AT1 receptors with losartan
prevented any change in CI and TPR induced by 17
-estradiol in the
presence of L-NAME. These
observations suggest that NO is necessary to offset a vasoconstrictor
action of angiotensin II, which is stimulated by estradiol
administration.
cardiac output; vascular resistance; estrogen; N
-nitro-L-arginine methyl ester
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