Increased Skin Blood Flow and Enhanced Heat Loss in Humans after Niacin Ingestion
ARMY RESEARCH INST OF ENVIRONMENTAL MEDICINE NATICK MA
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Healthy, young subjects were studied in three separate series of studies characterizing nicotinic acid NA ingestion 5 mg.kg-1. 1 At rest, seated T. - 30 deg C, rh 23 at 0800 h and again between 1800 and 2100 h. 2 At rest R and during seated exercise X, Ta 29 deg C, rh 30. 3 During upright exercise when wearing a protective clothing system Ta 28 deg C, rh 30. NA treatment resulted in decreased Tes, T.sk, SKBF, FBF, heart rate, and cutaneous vascular conductance CVC P0.05. NA decreased mean arterial pressure at rest. Subjects had no difficulty completing, seated or upright exercise in either control or NA experiments. The pharmacological manipulation of skin blood flow at rest and during moderate exercise effectively increased sensible heat flux during seated as well as upright exercise. NA ingestion also increased sensible heat flux from individuals dressed in chemical protective clothing. These experiments show that pharmacologic manipulation of skin blood flow by NA ingestion should be done cautiously, especially when NA will be used repeatedly or in novel circumstances. Niacin, Heat exchange, Cardiovascular responses, Skin blood flow.
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