Nitric oxide and exercise in the horse.

Abstract

1. The effects of exercise on the production rate of nitric oxide (NO) in exhaled air (VNO) and 20 1 min-', respectively, and induced cyclical changes in the breathing pattern.4. Exercise induced a linear increase in VNO with work intensity to a maximum (428 1 + 31'6 pmol min-' kg-) which coincided with the maximal oxygen uptake for the horses (138 3 + 11 7 ml min-' kg-), although a further increase in VNO (779 3 + 38-4 pmol min-' kg-') occurred immediately after exercise. The changes in VNo correlated well with the tidal volume (r = 0-968; P < 0-01) and the haematocrit (r = 0-855; P < 0-01). 5. In the first 2 min of high intensity exercise, inhaled NO (80 p.p.m.) significantly (P < 0 05) reduced the pulmonary artery pressure: during the first minute, pulmonary artery pressure was 83-1 + 7-6 mmHg compared with a control value of 94 4 + 6-3 mmHg, and during the second minute, 84-2 + 7-1 mmHg compared with a control value of 98-4 + 4-7 mmHg.There were no other significant changes in cardiovascular or respiratory indices, including cardiac output, measured during exercise between control and inhaled NO tests. 6. The results show that exhaled NO is released from the airways of the horse and may contribute to the regulation of pulmonary vascular tone during exercise.

Platelet-Activating Factor and Evidence of Oxidative Stress in the Bronchoalveolar Fluid of Thoroughbred Colts during Race Training

“…A limited NO production, as observed in the EX group, is expected in the airways of horses performing moderate or near‐maximal exercise, 34 explained by the exercise‐induced arterial hypoxemia (EIAH) described in horses during exercise 2,3,35 . EIAH results in hypoxic inhibition of NO production, depressing endothelium‐dependent relaxation of the vasculature 35 …”

Equine sweating and anhidrosis Part 1 – equine sweating

“…Heat stress increases cutaneous NO above basal levels, augmenting vasodilatation under these circumstances 136,137 . It has also been shown to cause vasorelaxation in blood vessels of various organs of the horse 127,138,139 . In humans, endurance training has been shown to enhance the vasodilatatory effects of NO in the dermal microcirculation 140 and Wang 141 has shown that the skin microvascular perfusion response to ACh, involving endothelium‐dependent NO production, is enhanced by moderate exercise training but reversed by detraining.…”

Body Temperature and Plasma Nitric Oxide Metabolites in Response to Standardized Exercise Test in the Athletic Horse

“…Oppositely, the use of a competitive inhibitor of NO synthase (L-Nitroarginine methyl ester, L-NAME) in exercising horses diminished sweating rate with elevated core and peripheral temperatures leading to deranged thermoregulation [1]. These effects may be related to peripheral vasoconstriction, but suggest possible modulation by NO of the central and peripheral sympathetic control of sweating.…”

“…The cardiovascular system responds to the tremendous increase in oxygen and substrate demand by muscles and central nervous system through a selective vasodilatation allowing an increase oxygen ad substrate delivery to these districts. At the same time, significant vasoconstriction, initially occurring in skin capillaries also, is observed in the enteric district [1].…”