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This Article Full Text Full Text (PDF) All Versions of this Article: 560/1/329    most recent jphysiol.2004.065664v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Jones, A. M Articles by Campbell, I. T Search for Related Content PubMed PubMed Citation Articles by Jones, A. M Articles by Campbell, I. T

¹ Department of Exercise and Sport Science, Manchester Metropolitan University, Hassall Road, Alsager, ST7 2HL, UK
² Department of Anaesthesia, Wythenshawe Hospital, Manchester, M23 9LT, UK

We hypothesized that the effective inhibition of nitric oxide synthase (NOS), achieved via systemic infusion of N^G-nitro-L-arginine methyl ester (L-NAME), would reduce the gas exchange threshold (GET) and the maximal oxygen uptake (_O2max) during incremental cycle exercise in man if NO is important in the regulation of muscle vasodilatation. Seven healthy males, aged 18–34 years, volunteered to participate in this ethically approved study. On two occasions, the subjects completed an incremental exercise test to exhaustion on an electrically braked cycle ergometer following the infusion of either L-NAME (4 mg kg^–1 in 50 ml saline) or placebo (50 ml saline, CON). At rest, the infusion of L-NAME resulted in a significant increase in mean arterial pressure (MAP; CON vs. L-NAME, 89 ± 8 vs. 103 ± 11 mmHg (mean ± S.D.; P < 0.05)) and a significant reduction in heart rate (HR; CON vs. L-NAME, 60 ± 12 vs. 51 ± 8 beats min^–1; P < 0.01). At submaximal work rates, there was no significant difference in _O2 between the conditions and no difference in the GET (CON vs. L-NAME, 1.94 ± 0.47 vs. 2.01 ± 0.41 l min^–1). However, at higher work rates, differences in _O2 between the conditions became more pronounced such that _O2max was significantly lower with L-NAME (CON vs. L-NAME, 4.02 ± 0.41 vs. 3.80 ± 0.34 l min^–1; P < 0.05). The reduction in _O2max was associated with a reduction in HR_max (CON vs. L-NAME, 186 ± 10 vs. 178 ± 7 beats min^–1; P < 0.01). These results demonstrate that NOS inhibition with L-NAME has no effect on GET but reduces _O2max during large muscle group exercise in man, presumably by direct or indirect effects on cardiac output and muscle blood flow.

(Received 1 April 2004; accepted after revision 28 July 2004; first published online 29 July 2004)
Corresponding author A. M. Jones: Department of Exercise and Sport Science, Manchester Metropolitan University, Hassall Road, Alsager, ST7 2HL, UK. Email: a.m.jones{at}mmu.ac.uk

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