CHANGES IN CREATINE KINASE ISOENZYME COMPOSITIONS OF SKELETAL AND HEART MUSCLES DURING EXERCISE TRAINING IN RATS

The effect of swimming training on creatine ki nase (CK) isoenzyme compositions (cytoplasmic CK : CK-MM, -MB, -BB ; mitochondrial CK : m-CK) of coleus (SOL), extensor digitorum longus (EDL) and heart muscles were studied. Wistar strain male rats were trained by swimming at a water temperature of 38±2°C, loaded with a weight equal to 5% of their body weight attached to their tails, and made to swim 4-days per week from the age of 4 weeks old for 4, 6 and 8 weeks. CK isoenzyme compositions of SOL, EDL and heart were different from those of other muscles. The activities of CK-MB and m-CK of SOL, EDL and heart increased following exercise training. CK isoenzyme composition of skeletal muscle (SOL and EDL) tended to qualitatively resemble the heart with training. These results suggest that the training-induced metabolic change in skeletal muscle causes similar CK isoenzyme composition to the heart muscle, and ensure energy production for the continuous muscle contraction during endurance exercise. The possibility that the source of the increased serum CK-MB activity after exercise is from the skeletal muscle should be examined thoroughly when the high serum CK-MB activity is interpreted.