Submitted on June 24, 2008
Revised on November 24, 2008
Accepted on January 5, 2009
Non-selective NOS inhibition blunts the sweat response to exercise in a warm environment
Garrett Welch1, Kristopher M. Foote1, Crystelle Hansen1, and Gary W. Mack1*
1 Brigham Young University
* To whom correspondence should be addressed. E-mail: gary_mack{at}byu.edu.
The role of nitric oxide synthase (NOS) inhibition in modulating human thermoregulatory control of sweating and cutaneous dilation was examined in 10 subjects (5 male/5 female). Three intradermal microdialysis probes were placed in non-glabrous skin of the dorsum of the forearm. The control site was perfused with 0.9% saline while the two remaining sites were perfused with a NOS inhibitor: 10 mM NG-nitro-L-arginine (L-NAME) or 10 mM NG-monomethyl-L-arginine (L-NMMA). Local sweat rate (SR) and skin blood flow (laser Doppler velocimetry) were monitored directly over the path of the intradermal microdialysis probe while arterial blood pressure was measured in the opposite arm non-invasively. Thermoregulatory responses were induced by cycle ergometer exercise (60% VO2max) in a warm environment (30°C). Esophageal temperature increased 1.5 ± 0.2 °C during the 30 min of exercise. The cutaneous dilator response between 5 and 30 min of exercise in the heat was attenuated by both 10 mM L-NAME and 10 mM L-NMMA (p<0.05). However, 10 mM L-NAME was more effective in blunting the rise in cutaneous vascular conductance during exercise than L-NMMA (p<0.05). NOS inhibition also reduced the rise in local SR between 10 and 30 min of exercise (p<0.05). In this case10 mM L-NMMA was more effective in limiting the increase in local SR than 10 mM L-NAME (p<0.05). We conclude that local production of nitric oxide in the skin or around the sweat gland augments local SR and cutaneous dilation during exercise in the heat.
