title: Angiotensin II enhances beta-adrenergic receptor-mediated vasorelaxation in aortas from young but not old rats.
abstract: 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.
authors.affiliation: Research Service, Portland Veterans Affairs Medical Center, Portland, Oregon 97201, USA.
authors.forename: W E
authors.initials: WE
authors.lastname: Schutzer
authors.forename: H
authors.initials: H
authors.lastname: Xue
authors.forename: J F
authors.initials: JF
authors.lastname: Reed
authors.forename: J B
authors.initials: JB
authors.lastname: Roullet
authors.forename: S
authors.initials: S
authors.lastname: Anderson
authors.forename: S L
authors.initials: SL
authors.lastname: Mader
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000502:physiology*; D003994:Bucladesine / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology; D008297:Male; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D020239:Receptor Cross-Talk / Q000187:drug effects / Q000502:physiology; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology*
chemical_list: D000318:Adrenergic beta-Agonists; D007093:Imidazoles; D010726:Phosphodiesterase Inhibitors; D011725:Pyridines; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; C073402:PD 123319; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP; D007545:Isoproterenol; D015056:1-Methyl-3-isobutylxanthine