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Horm Metab Res 2002; 34(9): 516-522
DOI: 10.1055/s-2002-34792
Original Clinical
© Georg Thieme Verlag Stuttgart · New York

Effects of Ovariectomy on Indices of Insulin Resistance, Hypertension, and Cardiac Energy Metabolism in Middle-Aged Spontaneously Hypertensive Rats (SHR)

A.  Swislocki 1 , E.  S.  Burgie 2 , K.  J.  Rodnick 2
  • 1Medical Service, VA Northern California Health Care System, Martinez, CA, and Department of Medicine, University of California, Davis, School of Medicine, Davis, CA, USA
  • 2Department of Biological Sciences, Idaho State University, Pocatello, ID, USA
Presented in part at the 13th Meeting of the American Society of Hypertension, New York, May, 1998.
Further Information

Publication History

Received: 8 November 2001

Accepted after revision: 15 May 2002

Publication Date:
17 October 2002 (online)

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Abstract

Insulin resistance is a risk factor for coronary heart disease. The protection of young women from coronary events is sharply reduced with menopause. To assess the impact of menopause on glucose tolerance, insulin resistance, body weight gain, heart size, and cardiac energy metabolism, we studied 28-week-old female SHR and Wistar-Kyoto (WKY) rats, who were either ovariectomized (SHROVX and WKYOVX) or sham-operated (SHRSHAM and WKYSHAM). Animals underwent blood-pressure measurement and an oral glucose tolerance test (OGTT). Hearts were weighed and assayed for metabolic enzyme activities. Female SHR were 33 % lighter and hypertensive (+ 36 mmHg), with 33 % larger hearts (when corrected for body weight differences) compared to WKY. Although ovariectomized animals of both strains were heavier overall than their sham-operated counterparts, when heart weights were corrected for body weight, both OVX strains had lighter hearts than both SHAM strains. Glucose and insulin responses during OGTT were similar between the four groups; however, free fatty acid (FFA) responses were approximately 50 % greater in SHR than WKY, although less in SHROVX than SHRSHAM. WKYOVX demonstrated 8 % lower ventricular hexokinase activity than WKYSHAM, which may reflect reduced cardiac glucose utilization. We also noted 16 % higher citrate synthase activity in WKY hearts. In conclusion, the insulin resistance characteristic of younger SHR is blunted in middle-aged female rats, although FFA responses remain elevated. Ovariectomy did not alter in vivo glucose tolerance in this group; however, sex hormones may be important in maintaining normal heart size and the potential for cardiac glucose metabolism.

Key words

Insulin Resistance - Hypertension - Cardiac Hypertrophy - Menopause

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A. Swislocki, M.D., F.A.C.P.

Medical Service (612/111) · VA Northern California Health Care System ·

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