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Department of Pharmacology, Brody School of Medicine, East Carolina University, Greenville, North Carolina 27858
Previous studies have
shown that estrogen modulation of endothelial nitric oxide (NO)
synthase (eNOS) may confer protection against heart disease.
Here, we demonstrate an association between reductions in
baroreflex-mediated bradycardia and in cardiac NOS activity in
ovariectomized (Ovx) rats compared with controls. The latter resulted,
at least in part, from a reduction in cardiac eNOS protein.
eNOS-derived NO and its biological effects are determined by the levels
of eNOS protein and by eNOS catalytic activity; the latter is regulated
partly through the dynamic interaction with an inhibitory protein
(caveolin) and a stimulatory protein (calmodulin). The association of
eNOS immunoprecipitated with caveolin-3 and calmodulin was examined.
Caveolin-3 and calmodulin binding with eNOS was increased and
decreased, respectively, in Ovx rats. 17
-Estradiol replacement
restored, to within normal levels, the baroreflex-mediated bradycardic
responses along with eNOS activity, eNOS expression, and the
association of eNOS with caveolin-3 and calmodulin. Our findings may
help to elucidate the molecular mechanism underlying the favorable
effects of estrogen on cardiac responses to baroreflex activation.
nitric oxide; 17
-estradiol; baroreflex sensitivity
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