Metabolic changes in exercise‐induced asthma

Abstract

Summary Five patients with a history of post‐exercise bronchoconstriction and eleven control subjects were exposed to gradually increasing work loads on a bicyle ergometer. The asthmatic patients showed higher blood lactic acid levels at all work loads than the control subjects. In contrast to findings in the controls, the plasma free fatty acid in the asthmatics failed to ‘rebound’ following the cessation of exercise; and in two out of three patients plasma FFA did not rise after epinephrine injection. In addition, the asthmatic patients consumed less oxygen during the exercise than the controls. The results of this study suggest that patients with post‐exercise asthma may have to rely more on carbohydrates as the main source of energy because of the reduced availability of FFA. Since the consumption of oxygen is also reduced, this may lead to a higher lactate production.

A critical assessment of the roles of circulating hydrogen ion and lactate in the production of exercise-induced asthma.

“…The neurological symptoms were believed to be the result of systemic alkalemia. During (2) and other laboratories (1,(3)(4)(5)(6)(7)(8)(9)(10)(11) has shown that postexertional bronchocon- (24) and perfusion of isolated skeletal muscle with hyperkalemic blood when the nerve is intact (25) produce an increase in ventilation typical of exercise, recent evidence demonstrates that neither hypocapnia nor hyperpnea are the mechanisms underlying exercise-induced asthma (26).…”

“…For a number ofreasons, this is an attractive hypothesis. First, the association between the induction of asthma and elevations in arterial hydrogen ion and/or lactate concentrations is quite common when one searches for it in the literature (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11). Second, because the acid end products of exercise are delivered to the airways and lung parenchyma by the bronchial and pulmonary arterial beds, and are freely permeable, they could possibly evoke intracellular events that promote generation or release of the mediators of immediate hypersensitivity (12)(13)(14).…”

Plasma cyclic nucleotide levels in exercise-induced asthma.

“…subjects repeated the protocol before and after inhalation of salbutamol aerosol, 1600 Htg daily for 18 days. This did not reduce the cAMP response to exercise, and we conclude that the diminished cAMP response of the asthmatic subjects was not caused by their medication.…”