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Departments of 1 Biomedical Engineering and 2 Anesthesiology and Critical Care Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21287
We hypothesized
that estradiol treatment would improve vascular dysfunction commonly
associated with obesity, hyperlipidemia, and insulin
resistance. A sham operation or 17
-estradiol pellet implantation was performed in male lean and obese Zucker rats. Maximal
vasoconstriction (VC) to phenylephrine (PE) and potassium chloride was
exaggerated in control obese rats compared with lean rats, but
estradiol significantly attenuated VC in the obese rats. Estradiol
reduced the PE EC50 in all groups. This effect was
cyclooxygenase independent, because preincubation with indomethacin
reduced VC response to PE similarly in a subset of control and
estrogen-treated lean rats. Endothelium-independent vasodilation (VD)
to sodium nitroprusside was similar among groups, but
endothelium-dependent VD to ACh was significantly impaired in obese
compared with lean rats. Estradiol improved VD in lean and obese rats
by decreasing EC50 but impaired function by decreasing
maximal VD. The shift in EC50 corresponded to an
upregulation in nitric oxide synthase III protein expression in the
aorta of the estrogen-treated obese rats. In summary, estrogen
treatment improves vascular function in male insulin-resistant, obese
rats, partially via an upregulation of nitric oxide synthase III
protein expression. These effects are counteracted by adverse factors,
such as hyperlipidemia and, potentially, a release of an
endothelium-derived contractile agent.
hormones; non-insulin-dependent diabetes mellitus; nitric oxide synthase; indomethacin; cyclooxygenase
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