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Title

Sex differences in mesenteric endothelial function of streptozotocin-induced diabetic rats: The role of endothelium-derived relaxing factors

Date of Award

2013

Document Type

Dissertation - Pacific Access Restricted

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Physiology and Pharmacology

First Advisor

Roshanak Rahimian

First Committee Member

Leigh Anderson

Second Committee Member

John Livesey

Third Committee Member

David Thomas

Fourth Committee Member

James Uchizono

Abstract

Several studies suggest that diabetes affects male and female vascular beds differently. However, the mechanisms underlying the interaction of sex and diabetes remain to be investigated. This study investigates whether there are 1) sex differences in the development of abnormal vascular responses and 2) changes in the relative contributions of endothelium-derived relaxing factors (EDRFs) in modulating vascular reactivity of mesenteric arteries taken from streptozotocin (STZ)-induced diabetic rats at early and intermediate stages of the disease (one and eight weeks, respectively). We also investigated the mesenteric expression of the mRNAs for endothelial nitric oxide synthase (eNOS) and NADPH oxidase (Nox) in STZ-induced diabetes in both sexes. Vascular responses to acetylcholine (ACh) in mesenteric arterial rings pre-contracted with phenylephrine were measured before and after pretreatment with indomethacin (cyclooxygenase inhibitor), L -NAME (NOS inhibitor), or barium chloride (K IR blocker) plus ouabain (Na + -K + ATPase inhibitor). We demonstrated that ACh-induced relaxations were significantly impaired in mesenteric arteries from both male and female diabetic rats at one and eight weeks. However, at eight weeks the extent of impairment was significantly greater in diabetic females than diabetic males. Our data also showed that in females, the levels of eNOS and Nox2- and Nox4-dependent NADPH oxidase mRNA expression and the relative importance of NO to the regulation of vascular reactivity were substantially enhanced, while the importance of endothelium-derived hyperpolarizing factor (EDHF) was significantly reduced at both one and eight weeks after the induction of diabetes. This study reveals the predisposition of female rat mesenteric arteries to vascular injury after the induction of diabetes, may be due to a shift away from a putative EDHF, initially the major vasodilatory factor, towards a greater reliance on NO, and the interaction of oxidative stress with elevated NO.

Pages

170

ISBN

9781303533921

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