DECLINE IN BETA-ADRENERGIC RECEPTOR-MEDIATED VASCULAR RELAXATION WITH AGING IN MAN

  • 1 December 1986
    • journal article
    • research article
    • Vol. 239  (3) , 802-807
Abstract
Beta adrenergic relaxation of vascular smooth muscle, mediated by cyclic AMP, is blunted with age in a variety of experimental animals. The applicability of these observations of man is uncertain. The dorsal hand vein technique provides an excellent method to examine the direct effects of aging on vascular responsiveness. Thirty-nine healthy male volunteers over the age range of 19 to 79 were studied. No differences in vascular responsiveness to phenylephrine, an alpha adrenergic agonist, were found for either the ED50 (dose producing 50% vasoconstriction) or Emax (maximum vasoconstriction attained). In marked contrast, vascular relaxation induced by isoproterenol, a beta adrenergic agonist, was significantly different in both the ED50 (dose producing 50% of maximum relaxation from a preconstricted state) and Emax (maximum relaxation attained). ED50 .+-. S.E.M. for the youngest and oldest deciles were 8.9 .+-. 2.3 and 60 .+-. 17.0 ng/min, respectively (P < .05); Emax .+-. S.E.M. were 96.7 .+-. 3.3 and 37.7 .+-. 8.7%, respectively (P < .001). Nitroglycerin, a smooth muscle relaxant whose effects are not mediated through the cyclic AMP system, was also used to examine the specificity of this blunted response to isoproterenol. Almost complete relaxation was achieved with the infusion of nitroglycerin in the older group. These results suggest that aging is associated with a specific decrease in beta adrenoreceptor-mediated vascular relaxation.