Influence of training and anabolic steroids on the LDH isozyme pattern of skeletal and heart muscle fibers of guinea pigs.

The influence of training and anabolic steroids (methandrostenolone) on the enzyme activity of the LDH system was investigated in 72 male guinea pigs. Sedentary animals and animals subjected to two different training regimens with and without anabolic steroids were compared in six groups each consisting of 12 guinea pigs. The training was performed on a rodent treadmill for 1 month, 30 min/day at an inclination of 45 degrees or 5 degrees, and at a speed of 30 m/min. Total LDH, its isozymes, and the composition of M and H subunits were determined enzymatically and by electrophoretical separation on cellulose acetate membrane in the following muscle fiber types; m. vastus lateralis white (FG) and red portion (FOG), m. soleus (SO), m. psoas major white (FG) and red portion (FOG), and in the left ventricle of the heart. The administration of anabolic steroids did not change the activity of total LDH or the composition of M and H subunits in sedentary animals. Exercise at 5 degrees inclination significantly reduced the total LDH and the concentration of H subunits in FOG, SO, and heart muscle fibers but not in FG muscle fibers. The additional application of anabolic steroids intensified these changes and also reduced the total LDH and the H subunit in FG as well as the M subunit in FOG, SO, and heart muscle fibers. After exercise at 45 degrees inclination with and without the application of anabolic steroids, the activity of LDH and its isozymes was identical to the values obtained in untrained animals but significantly higher than after the training at 5 degrees inclination. The typing of FG, FOG, and SO muscle fibers by the LDH isozyme pattern was not satisfactory, especially for the discrimination between FOG and SO fibers but also between FG and FOG fibers of muscle with different anatomic functions both in sedentary and trained animals.