Effects of short- and long-term exercise on urinary cGMP excretion in healthy subjects and in patients with coronary artery disease

The possibility that systemic formation of cyclic guanosine monophosphate (cGMP) could reflect the level of cardiovascular fitness was investigated. The relations between physical activity and systemic formation of cGMP were evaluated in healthy volunteers and in patients with coronary artery disease (CAD). No significant differences were observed in the basal urinary excretion of cGMP in highly trained runners, sedentary subjects, and in patients with CAD, despite the large differences in aerobic exercise training between groups. In addition, the basal levels of cGMP in CAD patients failed to increase after a 12-week cardiac rehabilitation program. Short term exercise, on the other hand, was associated with significant increases in urinary cGMP excretion. A 42-km marathon increased urinary cGMP excretion by 272%. The 15-km race increased urinary cGMP excretion by 330%. In CAD patients, 30 min of supervised exercise on a treadmill, at 80% of patient's maximal heart rate, induced a 60% increase in urinary cGMP, which returned to preexercise levels 90 min after termination of the exercise. Completion of the 12-week cardiac rehabilitation program improved exercise capacity and the magnitude of increase in cGMP levels induced by short-term treadmill exercise. Our findings suggest that cGMP increases during and shortly after short-term exercise and that the magnitude of the increase seems dependent on the intensity of the exercise and on physical fitness. Exercise training in healthy subjects and in CAD patients enhanced the amount of cGMP produced during short-term exercise, which might be responsible for some of the protective cardiovascular actions of exercise. The short half-life of cGMP may explain why the basal resting levels of cGMP are not appropriate predictors of a subject's physical fitness.