Men have higher blood pressure (BP) than premenopausal women. Pressor response to oxidative stress may be a major contributor to the sex difference in BP control. Mitochondrial oxidative stress is associated with hypertension; however, whether mitochondrial oxidative stress plays a role in the sex difference in BP is unknown. In the present study, we tested the hypothesis that mitochondrial oxidative stress contributes to the sex difference in BP regulation in spontaneously hypertensive rats (SHR). Young intact (iYMSHR) and castrated males (cYMSHR), and females SHR (YFSHR) (3 mos of age) were implanted with radiotelemeters, and after a 4 day baseline BP, were treated with mitoTempo (0.75 mg/kg/d, sc minipumps), a specific scavenger of mitochondrial superoxide, for 7 days. Following 10 days washout of mito-tempo, rats were treated with Tempol (30 mg/kg/day, po drinking water) for 7 days. iYMSHR have higher blood pressure (by telemetry) than cYMSHR and YFSHR (148±1 mmHg, n=5, vs 132±1 mmHg, n=5, and 139±1 mmHg, n=5; p<0.01, respectively). MitoTempo reduced BP by 6% in iYMSHR (147±1 vs 139±1, n=5; p<0.05) compared to females (3%: 139±1 vs 136±1; n=5; p: NS) and castrated males (4.5%: 132±1 vs 126±1, n=5; p<0.05). After 10 days washout, tempol reduced BP only in iYMSHR (144±1 vs 130±1 mmHg, n=5; p<0.05). Our results suggest that mitochondrial oxidative stress may contribute to BP regulation in male SHR, but has no effect in females. The data also suggest that the presence of testosterone is necessary for the pressor response to oxidative stress in males since Tempol had no effect on BP in castrated males. Further studies examining the effect of steroid hormones and mitochondria in BP regulation are necessary to elucidate the importance of mitochondrial oxidative stress on sex difference of hypertension.
Sex difference in sensitivity to adrenergic agents in hindquarter vessels of spontaneously hypertensive rats