title: Chronic exercise decreases adrenergic agonist-induced vasoconstriction in spontaneously hypertensive rats.
abstract: This study was conducted to investigate the effects of chronic exercise on adrenergic agonist-induced vascular responses in spontaneously hypertensive rats (SHR). Four-week-old male SHR and Wistar-Kyoto rats were divided into control and trained groups. The trained groups ran on a drum exerciser at 70% of peak oxygen consumption for 60 min/day 5 days/wk for 10 wk. Resting systolic blood pressure and heart rate were measured by a tail-cuff method, and changes in these parameters were considered as indexes of effective training. At the end of experiments, thoracic aortas and carotid arteries were isolated. Vasoconstricting 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 vasoconstricting responses to NE (10(-8) M) after treatment with N omega-nitro-L-arginine. Vasorelaxing responses to PHE or clonidine were also studied. Our results showed that 1) vasoconstricting responses to NE or PHE in the endothelium-intact thoracic aorta were reduced, whereas PHE- or clonidine-induced EDNO release was enhanced by exercise training, and 2) the latter could be eliminated by N omega-nitro-L-arginine. Therefore, training may decrease adrenergic agent-induced vasoconstricting responses by increasing their stimulated EDNO release in hypertensive and normotensive rats.
authors.affiliation: Department of Physiology, National Cheng-Kung University Medical College, Tainan, Taiwan, Republic of China.
authors.forename: H I
authors.initials: HI
authors.lastname: Chen
authors.forename: I P
authors.initials: IP
authors.lastname: Chiang
mesh_terms: D018663:Adrenergic Agents / Q000494:pharmacology*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure; D004305:Dose-Response Relationship, Drug; D006339:Heart Rate; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D009569:Nitric Oxide / Q000378:metabolism; D009638:Norepinephrine / Q000494:pharmacology; D010101:Oxygen Consumption; D010656:Phenylephrine / Q000494:pharmacology; D005082:Physical Exertion; D051381:Rats; D011918:Rats, Inbred SHR / Q000502:physiology*; D011921:Rats, Inbred WKY; D013997:Time Factors; D014661:Vasoconstriction
chemical_list: D018663:Adrenergic Agents; D000316:Adrenergic alpha-Agonists; D010656:Phenylephrine; D009569:Nitric Oxide; D009638:Norepinephrine