Nonselective NOS inhibition blunts the sweat response to exercise in a warm environment.
The role of nitric oxide synthase (NOS) inhibition in modulating human thermoregulatory control of sweating and cutaneous dilation was examined in 10 subjects (5 men and 5 women). Three intradermal microdialysis probes were placed in nonglabrous 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 nonselective NOS inhibitor: 10 mM N(G)-nitro-L-arginine (L-NAME) or 10 mM N(G)-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 noninvasively. Thermoregulatory responses were induced by cycle ergometer exercise (60% peak oxygen consumption) in a warm environment (30 degrees C). Esophageal temperature increased 1.5 +/- 0.2 degrees 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 case, 10 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.
Welch
Garrett
G
Department of Exercise Sciences, Brigham Young University, Provo, Utah 84602, USA.
Foote
Kristopher M
KM
Hansen
Crystelle
C
Mack
Gary W
GW
D001783:Blood Flow Velocity / Q000187:drug effects; D001794:Blood Pressure / Q000187:drug effects; D001831:Body Temperature / Q000187:drug effects / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005080:Exercise Test / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors*; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology; D012867:Skin / Q000098:blood supply / Q000187:drug effects / Q000201:enzymology; D013545:Sweat Glands / Q000187:drug effects / Q000502:physiology; D013546:Sweating / Q000187:drug effects* / Q000502:physiology; D019323:omega-N-Methylarginine / Q000494:pharmacology*
D004791:Enzyme Inhibitors; D019323:omega-N-Methylarginine; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester