ACUTE EXERCISE AND SKELETAL-MUSCLE ANTIOXIDANT AND METABOLIC ENZYMES - EFFECTS OF FIBER-TYPE AND AGE

Inhibition of metabolic enzyme activity has been associated with free radical stress in locomotor muscle with prolonged or intense exercise. However, it is not known whether such alterations with acute exercise in skeletal muscle are influenced by muscle fiber type or age. Twenty 4-mo-old and twenty 24-mo-old female Fischer-344 rats were divided at random into young exercised (YE; n - 10), old exercised (OE; n = 10), young control (YC; n = 10), and old control (OC; n = 10) groups. Anim als in both YE and OE groups ran on a treadmill (10% uphill grade) for 40 min at approximately 75% of each age-group's maximal O2 consumptio n. Immediately after the treadmill run, white gastrocnemius (WG), red gastrocnemius (RG), and soleus (SOL) muscles were removed and quick-fr ozen in liquid nitrogen. Malondialdehyde was significantly increased ( P < 0.05) in RG of YE vs. YC rats. Glutathione peroxidase activity was significantly elevated (P < 0.05) in the WG of YE rats. Analysis of v ariance revealed a significant overall increase in superoxide dismutas e activity with exercise. Activities of phosphofructokinase (PFK), cit rate synthase, succinate dehydrogenase, and 3-hydroxyacyl-CoA dehydrog enase were unchanged (P > 0.05) with acute exercise in the SOL. Howeve r, PFK activity was decreased in the WG by 60% in OE but only 33% in Y E, and in the RG by 41% in OE but only 21% in YE. We conclude that max imal glycolytic flux in the gastrocnemius may be adversely affected by acute exercise, and this effect was more pronounced in the 24-mo-old group.