Vol. 279, Issue 6, H2807-H2814, December 2000
Angiotensin II enhances 
-adrenergic
receptor-mediated vasorelaxation in aortas from young but not old
rats
William E.
Schutzer1,
Hong
Xue2,
John F.
Reed1,
Jean-Baptiste
Roullet2,
Sharon
Anderson1,2, and
Scott L.
Mader1,2
1 Research Service, Portland Veterans Affairs Medical
Center, and 2 Oregon Health Sciences University, School of
Medicine, Portland, Oregon 97201
-Adrenergic receptor
(-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
-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 -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 -AR-dependent vasorelaxation.
We conclude aging may affect a factor common to both ANG II-receptors
and -AR signaling pathways or aging may impair cross-talk between
these two receptor pathways.
cAMP; Fischer 344; forskolin; hypertension; isoproterenol
