title: Effects of different levels of exercise volume on endothelium-dependent vasodilation: roles of nitric oxide synthase and heme oxygenase.
abstract: The objective of this study was to examine the effects of moderate and high levels of exercise volume on endothelium-dependent vasodilation and associated changes in vascular endothelial/inducible nitric oxide synthase (eNOS and iNOS) and heme oxygenase (HO). Male Sprague-Dawley rats were assigned to sedentary control, acute (2 weeks), or chronic (6 weeks) treadmill running at moderate intensity (50% maximal aerobic velocity) with different durations of exercise episodes: 2 h/d (endurance training, moderate volume) and 3 h/d (intense training, high volume). Endothelium-dependent vascular function was examined in isolated thoracic aorta. Co-localization and contents of aortic eNOS/iNOS and HO-1/HO-2 were determined with immunofluorescence and Western blotting. Compared with sedentary controls, rats subjected to acute and chronic endurance training showed enhanced endothelium-dependent relaxation (p<0.01). Whereas acetylcholine-induced dilation was inhibited completely by NOS inhibitor N(omega)-nitro-L-arginine methyl ester (L-NAME) in sedentary controls, the dilation in the training groups was only partly blocked by L-NAME (inhibition was 98+/-3%, 79+/-6%, and 77+/-5% in sedentary control, acute, and chronic training groups, respectively, p<0.01). The remnant dilation in the training groups was further inhibited by HO inhibitor protoporphyrin IX zinc, with concomitant elevation in aortic eNOS as well as HO-1 and HO-2. In contrast to endurance exercise, high-volume intense training resulted in mild hypertension with significant impairment in endothelium-dependent vasodilation and profuse increases in aortic iNOS and eNOS (p<0.01). In conclusion, endothelium-dependent vasodilation is improved by endurance exercise but impaired by chronic intense training. Elevations of vascular eNOS and HO-1/HO-2 may contribute to enhanced vasodilation, which can be offset by intense training and elevation in vascular iNOS.
authors.affiliation: Department of Pharmacology, Shanghai Jiao Tong University School of Medicine, Shanghai, P.R.China.
authors.forename: Meng-Wei
authors.initials: MW
authors.lastname: Sun
authors.forename: Mei-Fang
authors.initials: MF
authors.lastname: Zhong
authors.forename: Jun
authors.initials: J
authors.lastname: Gu
authors.forename: Feng-Lei
authors.initials: FL
authors.lastname: Qian
authors.forename: Jian-Zhong
authors.initials: JZ
authors.lastname: Gu
authors.forename: Hong
authors.initials: H
authors.lastname: Chen
mesh_terms: D000818:Animals; D001011:Aorta / Q000201:enzymology; D004730:Endothelium, Vascular / Q000201:enzymology; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D009566:Nitrates / Q000097:blood; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D009573:Nitrites / Q000097:blood; D010805:Physical Conditioning, Animal / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014664:Vasodilation / Q000502:physiology*
chemical_list: D009566:Nitrates; D009573:Nitrites; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; C496318:Nos2 protein, rat; C496316:Nos3 protein, rat; D006419:Heme Oxygenase (Decyclizing); C491523:Hmox1 protein, rat; C105245:heme oxygenase-2