EXERCISE TRAINING DOES NOT ALTER CYTOCHROME-P-450 CONTENT AND MICROSOMAL METABOLISM

The purpose of this investigation was to determine whether increased e ndurance exercise capacity alters total hepatic cytochrome P-450 conte nt and cytochrome P-450 (CYP1A and CYP2B) mediated hepatic microsomal mixed-function oxidase drug metabolism. Twenty adult male Sprague-Dawl ey rats were randomly assigned to either a control (C) or an endurance trained group (ET). ET rats were progressively trained 5 d.wk(-1) for 11 wk. Both C and ET rats were administered in random order single po sttraining doses of probe drugs theophylline (probe for CYP1A) and ant ipyrine (probe for CYP2B). Soleus muscle citrate synthase activity of ET rats was significantly greater (P < 0.01) than for C rats (mean +/- SD; C,26.4 +/- 1.3 mu mol.g(-1).min(-1); ET, 46.1 +/- 2.7). In contra st, total liver cytochrome P-450 content was not significantly differe nt (P > 0.01) among C and ET rats (mean +/- SD; C, 0.554 +/- 0.055 nmo l.mg(-1) liver protein; ET, 0.604 +/- 0.080). Likewise, the posttraini ng C and ET single-sample plasma clearances of theophylline (mean +/- SD; C,1.89 +/- 0.360 l.h(-1).kg(-1) total liver weight; ET, 2.08 +/- 0 .49) and antipyrine (mean +/- SD; C, 6.44 +/- 1.56 l.h(-1).kg(-1) tota l liver weight; ET, 6.51 +/- 1.02) were not significantly different (P > 0.01). Therefore, it was concluded that strenuous endurance trainin g of 11 wk duration did not alter total hepatic cytochrome P-450 conte nt or CYP1A or CYP2B activity.