Angiotensin II enhances beta-adrenergic receptor-mediated vasorelaxation in aortas from young but not old rats.

beta-Adrenergic receptor (beta-AR)-mediated (cAMP-dependent) vasorelaxation declines with advancing age. It has been shown that angiotensin II (ANG II), a potent vasoconstrictor, enhances cAMP-mediated vasorelaxation. Therefore, we questioned whether ANG II could reverse age-related, impaired beta-AR-mediated vasorelaxation and cAMP production. Pretreatment of aortic rings from 6-wk-old or 6-mo-old male Fischer 344 rats with ANG II significantly enhanced vasorelaxation induced by isoproterenol (Iso), a beta-AR agonist, and forskolin, a direct activator of adenylyl cyclase, but not dibutyryl-cAMP or isobutylmethylxanthine. The ANG II effect was blocked by losartan but not PD-123319 and was not observed in the aortas from 12- and 24-mo-old animals. Iso-stimulated cAMP production in the aorta was enhanced in the presence of ANG II in the 6-wk-old and 6-mo-old age groups only. Results suggest ANG II cannot reverse the age-related impairment in beta-AR-dependent vasorelaxation. We conclude aging may affect a factor common to both ANG II-receptors and beta-AR signaling pathways or aging may impair cross-talk between these two receptor pathways.