Alterations in the expression and activity of creatine kinase-M and mitochondrial creatine kinase subunits in skeletal muscle following prolonged intense exercise in rats

Creatine kinase (CK) isoenzymes are important structural and energy metabol ism components in skeletal muscle. In this study, CIC isoenzyme alterations were examined in male rats, with an 8% body mass weight attached to their tail. The rats were either forced to swim for 5 h (5S, n = 51), or were pre -trained for 8 days and then forced to swim for 5 h (T5S, n = 48). Rats wer e sacrificed either immediately (0 h PS), 3 h (3 h PS), or 48 h post-swimmi ng (48 h PS), Serum CK was increased significantly (P < 0.01) 6.2- and 2.0- fold at 0 h PS following the 5S and T5S protocols, respectively. However, t raining (T5S protocol) significantly (P < 0.01) decreased CI( release. Sole us and white gastrocnemius (WG) CK activity was significantly decreased fol lowing the 5S protocol (P < 0.05), but not following the T5S protocol. The CK-M activity of the soleus muscle was significantly(P < 0.05) decreased at 0 h FS following both the 5S and T5S protocols, and returned to control va lues at 3 h PS. The CK-M activity of the WG was significantly (P < 0.05) de creased at 0 h PS following the 5S protocol. Sarcomeric mitochondrial CK (s CK-Mit) was decreased significantly(P < 0.01) at 0 h PS (20%), 3 h PS (14%) , 24 h PS (22%), and 48 h PS (15%) following the 5S protocol. However, sCK- Mit was decreased significantly (P < 0.01) only at Oh PS (7%) following the T5S. The results of this study demonstrate that prolonged intense exercise causes a loss of skeletal muscle CK-M and sCK-Mit activity and that traini ng prior to the prolonged intense exercise attenuates the exercise-induced CK-M and sCK-Mit loss in both red and while skeletal muscles.