Glucocorticoid Uptake and Release by the Human Heart: Studies at Rest, during Prolonged Exercise, and during Nicotinic Acid Infusion

Arterial and coronary sinus plasma glucocorticoid concentrations have been measured in 18 healthy men, 9 of whom received a nicotinic acid infusion to decrease arterial FFA concentration. At rest, the arterial-coronary sinus difference was correlated with the arterial concentration, so that above 10 μg/ml plasma glucocorticoid was taken up from, and below released into, the blood. To some extent, this was related to arterial insulin concentration. Although arterial glucocorticoid concentration was not significantly changed by nicotinic acid or exercise, significant release of glucocorticoid from the heart took place during prolonged exercise in those subjects receiving nicotinic acid. This release was associated with a rise in arterial growth hormone concentration. The release of glucocorticoid, here occurring in a situation with limited FFA availability, might facilitate the myocardial uptake of glucose although the concomitant growth hormone increase might tend to counteract this effect.