Chronic exercise decreases adrenergic agonists-induced
vasoconstriction in spontaneously hypertensive rats.
Chen, Hsiun-Ing, and I-Ping Chiang.
Department of Physiology, National Cheng-Kung University Medical
College, Tainan, Taiwan 701, Republic of China
APStracts 3:0122H, 1996.
This study was conducted to investigate the effects of chronic
exercise on adrenergic agonists-induced vascular responses in
spontaneously hypertensive rats (SHR). Four-week-old male SHR and
Wistar-Kyoto rats were divided into control and trained groups
separately. The trained groups ran on a drum exerciser with an
intensity of 70% peak oxygen consumption for 60 min/d, 5 d/wk for 10
weeks totally. Resting systolic blood pressure and heart rates were
measured by a tail-cuff method, and changes in these parameters were
considered as indices of effective training. At the end of
experiments, thoracic aortae and carotid arteries were isolated.
Vasoconstrictive responses to norepinephrine (NE) or phenylephrine
(PHE) were studied. To clarify the role of endothelium-derived nitric
oxide (EDNO) in the alteration of NE-induced vasoconstriction after
chronic exercise, we measured the changes in vasoconstrictive
responses to NE (10-8 M) after treatment of Nw-nitro-L-arginine (L
-NNA). Vasorelaxing responses to PHE or clonidine were also studied.
Our results showed that 1) vasoconstrictive responses to NE or PHE in
the endothelium-intact thoracic aorta were reduced, while PHE or
clonidine-induced EDNO release was enhanced by exercise training; 2)
the latter could be eliminated by L-NNA. Therefore, training may
decrease adrenergic agents-induced vasoconstrictive responses by
increasing their stimulated EDNO release in hypertensive and
normotensive rats.
Received 31 October 1995; accepted in final form 12 March 1996.
APS Manuscript Number H1021-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 27 March 96