Differential effects of swimming and running on microsomal metabolism in middle-aged and aged Fischer 344 rats

Cytochrome P-450 (P-450) content as well as p-nitroanisole (pNA) O-demethylase and UDP-glucuronyltransferase (UDPGT) activities were determined in livers of middle-aged (MA; 12 or 18 months) and aged (24-26 months) rats exercised by either treadmill running or swimming. In addition, aniline hydroxylase activity was measured in MA runners and aged swimmers and compared to respective sham and non-handled controls. Treadmill exercise consisted of running aged and MA rats on a motorized treadmill for 16 and 20 m/min respectively, 60 min/day and 4 times per week, for 8 weeks. Sham rats were placed on the treadmill twice per week for 5 min at 8 m/min. No differences were found in any parameter comparing sham rats to non-handled controls. Running did not affect body weight or hepatic microsomal protein during the 8-week study. A 33-35% decline in microsomal P-450 content in treadmill exercised MA and aged rats was found. PNA O-demethylase activity was decreased 30% in MA and 45% in aged runners and aniline metabolism was inhibited 21% in MA rats. UDPGT activity was not affected by running in MA or aged rats. Swimming exercise was accomplished by placing the rats in a tank of water (32-33 degrees C) filled to a depth of 2 ft. Swim time was 60 min twice daily, 5 times per week. The aged and MA rats were trained for 6 months and 1 year, respectively. Two control groups, non-swimming sedentary (dry control) and 1 min swim/day sham (wet control), were utilized. MA and aged wet controls and swimmers weighted 8% and 15% less respectively, than MA and aged sedentary rats. Microsomal protein was significantly increased in MA swimmers compared to sedentary (20%) and wet control (35%) but no change was found with swimming in the aged rats. The results of the enzymatic studies were variable in the MA rats. Increases in P-450 content were found in wet controls (16%) and swimmers (27%) of the MA group, but only the swimming change was significant. No significant change was determined for pNA metabolism between swimmers and wet (22%) or dry (17%) controls. Aged swimmers and wet controls were more consistent, with no change in any of the parameters except aniline metabolism which was significantly increased in wet controls (25%) and swimmers (28%) as compared to dry controls. No significant change in UDPGT activity was measured in either age group of swimmers.(ABSTRACT TRUNCATED AT 400 WORDS)