Journal
JOURNAL OF CARDIOVASCULAR PHARMACOLOGY
Volume 36, Issue 2, Pages 176-181Publisher
LIPPINCOTT WILLIAMS & WILKINS
DOI: 10.1097/00005344-200008000-00006
Keywords
vascular contractility; hyperinsulinemia; hypertriglyceridemia; sexual dimorphism; JCR : LA-cp rat
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Vascular wall function was assessed in obese insulin-resistant (cp/cp) and lean normal (+/?), male and female, JCR:LA-cp rats. Both male and female cp/cp rats showed enhanced maximum contractility in response to norepinephrine; impaired smooth muscle in response to sodium nitroprusside, a nitric oxide (NO) donor, and impaired relaxation in response to acetylcholine (ACh), compared with their lean counterparts. The abnormalities were similar in male and female cp/cp rats. The NO synthase inhibitor, N-omega-nitro-L-arginine methyl ester (L-NAME), inhibited ACh-mediated relaxation significantly in male rats. both cp/cp and +/?. The inhibition of ACh-mediated relaxation by L-NAME in +/? females was less, with no reduction in maximal relaxation, ana was absent in cp/cp females. These effects suggest that the relative importance of NO in the endothelial modulation of smooth muscle contractility is greater in male rats. The results are consistent with a decreased role for endothelial NO in the cp/cp rats of both sexes and a reduction in NO-independent cholinergic relaxation in the male cp/cp rat. This NO-independent mechanism is not affected in the female cp/cp rats. The relatively small differences between males and females in smooth muscle cell and vascular function may contribute to sex-related differences in the atherogenesis, vasospasm, and ischemic damage associated with the obese insulin-resistant state.
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