Does local heating-induced nitric oxide production attenuate vasoconstrictor responsiveness to lower body negative pressure in human skin?
We tested the hypothesis that local heating-induced nitric oxide (NO) production attenuates cutaneous vasoconstrictor responsiveness. Eleven subjects (6 men, 5 women) had four microdialysis membranes placed in forearm skin. Two membranes were perfused with 10 mM of N(G)-nitro-L-arginine (L-NAME) and two with Ringer solution (control), and all sites were locally heated to 34 degrees C. Subjects then underwent 5 min of 60-mmHg lower body negative pressure (LBNP). Two sites (a control and an L-NAME site) were then heated to 39 degrees C, while the other two sites were heated to 42 degrees C. At the L-NAME sites, skin blood flow was elevated using 0.75-2 mg/ml of adenosine in the perfusate solution (Adn + L-NAME) to a similar level relative to control sites. Subjects then underwent another 5 min of 60-mmHg LBNP. At 34 degrees C, cutaneous vascular conductance (CVC) decreased (Delta) similarly at both control and L-NAME sites during LBNP (Delta7.9 +/- 3.0 and Delta3.4 +/- 0.8% maximum, respectively; P > 0.05). The reduction in CVC to LBNP was also similar between control and Adn + L-NAME sites at 39 degrees C (control Delta11.4 +/- 2.5 vs. Adn + L-NAME Delta7.9 +/- 2.0% maximum; P > 0.05) and 42 degrees C (control Delta1.9 +/- 2.7 vs. Adn + L-NAME Delta 4.2 +/- 2.7% maximum; P > 0.05). However, the decrease in CVC at 42 degrees C, regardless of site, was smaller than at 39 degrees C (P < 0.05). These results do not support the hypothesis that local heating-induced NO production attenuates cutaneous vasoconstrictor responsiveness during high levels of LBNP. However, elevated local temperature, per se, attenuates cutaneous vasoconstrictor responsiveness to LBNP, presumably through non-nitric oxide mechanisms.
Low
David A
DA
Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, TX 75231, USA.
Shibasaki
Manabu
M
Davis
Scott L
SL
Keller
David M
DM
Crandall
Craig G
CG
D000241:Adenosine / Q000494:pharmacology; D000328:Adult; D001794:Blood Pressure; D045462:Endothelium-Dependent Relaxing Factors / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D006339:Heart Rate; D006358:Hot Temperature; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology*; D008150:Lower Body Negative Pressure; D008297:Male; D017551:Microdialysis; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D012039:Regional Blood Flow; D012107:Research Design; D012867:Skin / Q000098:blood supply* / Q000378:metabolism; D012881:Skin Temperature; D014661:Vasoconstriction / Q000187:drug effects
D045462:Endothelium-Dependent Relaxing Factors; D004791:Enzyme Inhibitors; D009569:Nitric Oxide; D019001:Nitric Oxide Synthase; D000241:Adenosine; D019331:NG-Nitroarginine Methyl Ester