EXERCISE-INDUCED CHANGES IN ENZYMATIC O-METHYLATION OF CATECHOLESTROGENS BY ERYTHROCYTES OF EUMENORRHEIC WOMEN

The present study was designed to assess the effects of acute exercise and short-term intensive training an calechol-O-methyltransferase (CO MT) activity. COMT inactivates catecholamines and converts primary cat echolestrogens (CE) into their O-methylated form yielding the 2-(2-MeO E) and 4-methoxyestrogens (4-MeOE). Blood samples were obtained from 1 5 previously untrained eumenorrheic women (mean +/- SE, (V)over dotO(2 max): 43.8 mL.kg(-1).min(-1) +/- 0.6) before and after a 5-d intensive training period, at rest and during incremental exercise. COMT activi ty was determined in the erythrocytes (RBC COMT) after incubation of b lood lysate with primary CE. The formation of both 2- and 4-MeOE was s ignificantly higher (P < 0.05) during the luteal (LPh) than during the follicular phase (FPh). The amount of 2-MeOE formed (FPh: 4.2 +/- 0.2 %; LPh: 4.9 +/- 0.2%) was significantly greater than the produced amou nt of 4-MeOE (FPh: 1.4 +/- 0.1%; LPh: 1.5 +/- 0.1%) (P < 0.05). Both b efore and after training, incremental exercise did not significantly a lter RBC-COMT activity although we observed a trend for RBC-COMT activ ity increasing proportionally with the exercise intensity. After a bri ef period of exhaustive training. during rest the formation of 2-MeOE (FPh: +16.7%, LPh: +15.7%) and 4-MeOE (FPh: +28.6%; LPh: +40%) was sig nificantly (P < 0.05) increased. The results of the present study are consistent with earlier findings reporting increased plasma concentrat ions of O-methylated CE following training, It is concluded that RBC-C OMT activity is increased by brief intensive training, but not by acut e exercise. We speculate that an increase in COMT-catalyzed O-methylat ion of CE may indicate that less COMT is available to deactivate norep inephrine.