DIFFERENCES IN THE CHANGE IN THE TIME-COURSE OF PLASMA ENDOTHELIN-1 AND ENDOTHELIN-3 LEVELS AFTER EXERCISE IN HUMANS - THE RESPONSE TO EXERCISE OF ENDOTHELIN-3 IS MORE RAPID THAN THAT OF ENDOTHELIN-1

Several studies have indicated that endothelin-1 (ET-1) and endothelin -3 (ET-3) are produced by different cells. Although ET-1 is produced b y vascular endothelial cells, these cells do not produce ET-3. The pre sence of ET-3 in the brain of several species suggests that ET-3 is a novel neuropeptide. It is unclear whether there are differences in the release of ET-1 and ET-3 under various physiological conditions in hu mans. In the present study, we measured the plasma concentrations of b oth ET-1 and ET-3 before and after endurance exercise on a cycle ergom eter. Male athletes exercised on a cycle ergometer for 30 min at inten sity of 130% of their individual ventilatory threshold (VT), which is intense exercise. Plasma ET-1 and ET-3 were greatly elevated by exerci se, but there was a marked difference in the time-course of the change in plasma concentration between the two peptides. The level of ET-1 p eaked 30 min after exercise, whereas that of ET-3 peaked immediately a fter exercise. Thus, plasma ET-3 increased faster than plasma ET-1 aft er exercise. The exercise-induced change in the time course in plasma ET-3, but not in ET-1, is similar to that in plasma norepinephrine whi ch is a neurotransmitter, suggesting that the rapid elevation in plasm a ET-3 is partly attributable to the neuronal response to exercise. Th e observed difference in the change in the time course of plasma ET-1 and ET-3 levels suggests that the mechanisms by which exercise alters the release and/or synthesis of these two peptides differ.