Nonselective NOS inhibition blunts the sweat response to exercise in a warm environment

Abstract

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.

Skin blood flow differentially affects near-infrared spectroscopy-derived measures of muscle oxygen saturation and blood volume at rest and during dynamic leg exercise

“…We tested this assumption in humans by assessing the influence of cutaneous vasodilation, induced by locally applied heat, on vastus lateralis SmO 2 and [tHb] measured at rest and during dynamic knee extension exercise. Local heating of the thigh caused marked increases in thigh skin blood flow, with the 42°C stimulus inducing a similar magnitude of vasodilation (*52-55% CVC peak ) to that previously reported in young adults after 30 min cycling at 60% peak O 2 consumption (*59% CVC peak ; [Welch et al 2009]). Cutaneous vasodilation caused small increases in resting SmO 2 (Table 2; Fig.…”

Response of lactating cows to live yeast supplementation during summer

“…Niacin can stimulate skin vasodilation (Benyó et al, 2006;Maciejewski-Lenoir et al, 2006) acting on vascular prostaglandin receptors (Cheng et al, 2006) and increase peripheral heat loss in dairy cows (Di Costanzo et al, 1997;Zimbelman et al, 2010). Nitric oxide synthase, a signaling molecule plausibly responsive to niacin, has also been shown to act on cutaneous thermoregulatory blood flow and sweat secretion in humans (Welch et al, 2009). Wrinkle et al (2012) observed a decrease in respiratory frequency of dairy cows in response to niacin supplementation.…”

Regional variations in transepidermal water loss, eccrine sweat gland density, sweat secretion rates and electrolyte composition in resting and exercising humans

“…The active sweat glands for one region (axilla) have not been investigated, so this value was taken to be 90% of that reported in Table 1. Sources: Clark and Lhamon [60], Ogata [63], Randall [64], Thompson [65], Willis et al [66], Roberts et al [78], Sato and Dobson [85], Inoue et al [86], Kondo et al [87], Peter and Wyndham [88], Buono [89], Gibson and Shelley [90], MacKinnon [91] (with the original calculation error corrected), Collins et al, [92], Hellon and Lind [93], Silver et al [94], Ojikutu [95], Sargent and Weinman [96], Juniper and Dykman [97], Toda [98], Bar-Or et al [99], Knip [100], Knip [101], Schaefer et al [102], Catania et al [103], Behm et al [104], Inoue et al [105], Kondo et al [106], Inoue et al [107], Welch et al [108] and Madeira et al [109]. …”