Administration of Atrial Natriuretic Peptide Does Not Modulate Sweating or Cutaneous Vasodilation in Young Men Exercising in the Heat

Abstract

Atrial natriuretic peptide (ANP) is a hormone secreted by cardiac muscle cells in response to increases in right atrial pressure, which can occur due to changes in blood pressure and blood volume. This hormone is also secreted during acute exercise in both temperate and hot environments and may be released into the blood due to the effects of increased venous return on the heart caused by active muscle contraction under these conditions. However, ANP release is diminished during prolonged exercise, which may ultimately impair heat loss if its release is linked to alterations in cutaneous blood flow and sweating. The current evidence is mixed with respect to a direct role of ANP in modulating cutaneous vasodilation and sweating responses, with some studies demonstrating an effect of exogenous ANP infusion in augmenting these heat loss responses, while others have failed to show any influence of the hormone. Thus, the purpose of this study was to evaluate the effects of intradermal administration of varying doses of ANP on cutaneous vasodilation and sweating responses in healthy habitually active young men exercising in a hot environment. Ten healthy young males (27 ± 6 years) exercised for 50 min at ~55% VO2peak in the heat (35°C, 20% relative humidity). Cutaneous vascular conductance (CVC, measured via laser Doppler flowmetry) and sweating (measured via ventilated capsules) were assessed at four dorsal forearm skin sites receiving either lactated Ringer's solution (Control) or one of three ANP doses (0.1 μM, 1.0 μM, 10 μM) via microdialysis. At the end of exercise, CVC was not different between Control (73 ± 14% CVCmax) and 0.1 μM (66 ± 20% CVCmax), 1.0 μM (69 ± 21% CVCmax), or 10 μM (71 ± 18% CVCmax) ANP sites (all P > 0.05). Similarly, sweat rates were not different between Control (1.37 ± 0.43 mg/min/cm2) and 0.1 μM (1.43 ± 0.55 mg/min/cm2), 1.0 μM (1.44 ± 0.41 mg/min/cm2), or 10 μM (1.36 ± 0.37 mg/min/cm2) ANP sites (all P > 0.05). In summary, these results demonstrate that in healthy habitually active young men, intradermal administration of ANP does not augment cutaneous vasodilation or sweating during exercise in the heat. Such findings may indicate that ANP does not have a direct effect on these heat loss responses. Alternatively, it may be the case that endogenous levels of ANP produced under these conditions are sufficient to elicit a maximal effect of the hormone on cutaneous blood flow and sweating in healthy young men, thus masking any direct effects of exogenous administration.Support or Funding InformationFunding support: Canadian Institutes of Health Research (held by Dr. Kenny).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.