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

Abstract

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 mins 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°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 weighed 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%) bu 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. Thus, while runing resulted in consistent results including an inhibition of P-450 content and activity within and between age groups, swimming results were variable and most changes included the wet control. Therefore, the results of the swimming study appear to be influenced by some components associated with exposuer to the water which may or may not be related to the exercise itself.