Effects of oestrogen treatment and angiotensin-converting enzyme inhibition on the microvasculature of ovariectomized spontaneously hypertensive rats.

We investigated the role of oestrogen in the function and structure of the microcirculation of female spontaneously hypertensive rats (SHRs), and evaluated the effect of 17beta-oestradiol on their cardiovascular response to pharmacological agents that block the formation of angiotensin II. Ten-week-old SHRs were randomly assigned to the following groups: intact, ovariectomized, and ovariectomized treated with 17beta-oestradiol (1.5 mg delivered over 60 days) and/or captopril (5 mg kg(-1) day(-1) for 8 weeks). Systolic blood pressure was determined from the time of ovariectomy up to 18 weeks of age, at which time endothelial function and microvascular density in skeletal muscle were evaluated. Both 17beta-oestradiol and captopril prevented development of hypertension in ovariectomized rats. Furthermore, coadministration of both drugs had a greater antihypertensive effect than either one alone. Acetylcholine-induced vasodilatation was impaired in ovariectomized SHRs, and the response was improved by treatment with 17beta-oestradiol and/or captopril. In addition, 17beta-oestradiol replacement in ovariectomized rats enhanced the effect of captopril on acetylcholine-induced vasodilatation. Ovariectomized rats also showed lower microvascular density than intact rats, an effect that was prevented by 17beta-oestradiol replacement or captopril treatment and, to a significantly larger extent, by coadministration of both. We concluded that both 17beta-oestradiol and captopril attenuated the development of hypertension and improved the impairment in microvascular density of ovariectomized SHRs. Moreover, when simultaneously administered, oestradiol and captopril had an additive effect on blood pressure and the microvasculature.

17beta-estradiol exerts a beneficial effect on coronary vascular remodeling in the early stages of hypertension in spontaneously hypertensive rats.

OBJECTIVE: Estrogens may induce cardioprotective effects and prevent neointima formation in response to vascular injury in vivo. The present study evaluated the effect of 17beta-estradiol on myocardial arterial remodeling and on vascular mitogen-activated protein kinase expression in experimental hypertension. DESIGN: The experiments were performed in intact female spontaneously hypertensive rats (SHR), in SHR that were ovariectomized at 10 or 25 weeks of age, and in ovariectomized SHR that were supplemented with 17 beta-estradiol (OVX + E2, 1.5 mg every 8 weeks, subcutaneous pellets). RESULTS: At 18 weeks of age, in all myocardial arterioles and small arteries studied, we found significant increases in wall-to-lumen ratio in ovariectomized rats as compared with intact animals. 17beta-estradiol significantly reduced the wall-to-lumen ratio in OVX + E2 rats. Perivascular fibrosis of small coronary arteries was significantly increased by ovariectomy, and this effect was prevented by long-term treatment with 17beta-estradiol. Phosphorylated extracellular signal-regulated kinase 1/2 significantly increased in mesenteric arteries from ovariectomized animals and this effect was prevented by 17beta-estradiol. Wall-to lumen ratio and perivascular fibrosis were significantly higher in older intact animals at 33 weeks of age. However, neither ovariectomy nor estradiol replacement had any effect on long-term hypertension-induced vascular remodeling. CONCLUSIONS: These data suggest that estradiol may exert a beneficial effect by protecting the vasculature from hypertension-induced myocardial arterial remodeling in the early stages of hypertension, but not when chronic alterations are established after a long-term period of hypertension.