Comparison of age-related changes in prostaglandin E1 and beta-adrenergic responsiveness of vascular smooth muscle in adult males.

Aging in humans is associated with a general decline in beta-adrenergic receptor responsiveness. Whether this is a consequence of a defect at the receptor level or along the adenylate cyclase pathway is not known. Using a technique to measure compliance of dorsal hand veins, we investigated the venodilatory response to isoproterenol and prostaglandin E1 (PGE1), which interact with distinct membrane-bound receptors but activate the same adenylate cyclase system. Studies were conducted in 7 young (Y, less than 30 years) and 7 elderly (E, greater than 60 years) healthy male volunteers. Dilatation induced by isoproterenol (mean +/- SD) was 43 +/- 8% in E vs 97 +/- 17% in Y, p = .003. However, PGE, produced complete relaxation in both Y and E subjects (122 +/- 17% vs 97 +/- 19% respectively, p = .270). The sensitivity to PGE1 was not significantly different between the Y and E. Our results demonstrate that PGE1 is a potent venodilator in humans and that the age-related decline in vascular response is specific to beta-adrenoceptor agonists and does not reflect a generalized loss in responsiveness to adenylate cyclase coupled receptors.