Sex hormone replacement therapy reverses decreased venous distensibility in pharmacologically ovariectomized rats

Objective: To test the effect of female sex hormone depletion and replaceme nt on the distensibility and geometry of the saphenous vein in female rats. Design: Twenty Sprague-Dawley rats were pharmacologically ovariectomized by triptorelin. Ten of these animals received combined hormone replacement wi th estradiol and medroxyprogesterone acetate. The rest were given vehicle. Ten animals kept parallel without pharmacological ovariectomy served as con trols. After 3 months of treatment, a segment of the saphenous vein was dis sected. Pressure-diameter curves were recorded in relaxed, contracted, and control states using a microangiograph. Results: Pharmacological ovariectomy lowered venous wall distensibility mea sured in contraction (at P=8 mm Hg: 4.41 +/- 1.21*10(-3) m(2)/N vs. control : 0.79 +/- 0.14*10(-3) m(2)/N; p < 0.05). Hormone replacement partially res tored this value (1.8 +/- 0.49*10(-3) m(2)/N). No alterations in distensibi lity were found in the relaxed state. After adjusting for body weight, we found that pharmacological ovariectomy lowered venous inner radius significantly compared with control (p < 0.05), whereas hormone replacement increased it compared with pharmacological ova riectomy (p < 0.05) and more significantly compared with control (p < 0.01) . Conclusion: Sex hormone depletion induces significant alterations in venous distensibility, presumably by inducing initial remodeling of the venous wa ll. Hormone dependency of distensibility differed in relaxed and contracted states of the vein, so some alterations of contractile elements of the wal l may be hypothesized. Lower distensibility of the venous wall found after pharmacological ovariectomy could be part of the mechanism of predispositio n for postmenopausal hypertension. This can be reversed by female sex hormo ne replacement.