Aging reduces the responsiveness of coronary arteries from male Wistar rats to the vasodilatory action of testosterone

This study was performed to examine whether aging affects the vasodilatory effects of testosterone in the coronary arteries of male rats. Isolated cor onary arteries from young mature (3-4 months) and elderly (22-26 months) ma le Wistar rats were studied in a wire myograph. Contractile function and en dothelial function were assessed by measuring vasomotor responses to 10-100 mmol/l KCI, 0.1 mmol/l prostaglandin F-2 alpha (PGF(2 alpha)) and 10 mu mo l/l acetylcholine. Sensitivity to the vasodilatory effects of testosterone was assessed by constructing dose-response curves to concentrations between I mu mol/l and I mmol/l testosterone dissolved in water in vessels maximal ly preconstricted with PGF(2 alpha). The compliance characteristics of each vessel and serum testosterone levels from each animal were measured. Histo logical sections of myocardium were examined for differences in coronary ar tery morphology. Vessels from elderly animals were significantly more resis tant to the vasodilatory effects of testosterone than vessels from young an imals (P = 0.001 by analysis of covariance). Vessels from elderly animals w ere also significantly less compliant (7.32 +/- 0.43 mu m/mN, compared with 10.99 +/- 1.52 mu m/mN in young animals; P = 0.011), and the levels of cir culating testosterone in elderly animals were lower, but not significantly so (2.04 +/- 0.63 nmol/l compared with 3.88 +/- 1.7 nmol/l; P = 0.32). Vess els from elderly animals were less contractile in response to KCI than thos e from young animals (P = 0.004 by analysis of covariance). There were no s ignificant differences between the two groups in their responses to PGF(2 a lpha) or acetylcholine. Thus it is concluded that coronary arteries from el derly rats are significantly less sensitive to the vasodilatory effects of testosterone than those from young animals.