title: Creatine kinase-MB isoenzyme adaptations in stressed human skeletal muscle of marathon runners.
abstract: The creatine kinase (CK) isoenzyme composition was determined in serial gastrocnemius muscle biopsies obtained from 12 male marathon runners. The mean muscle CK-MB composition significantly increased after chronic exercise (training) from 5.3% (pretraining) to 7.7% (premarathon) as well as after acute exercise (postmarathon) to 10.5% of the total CK activity (P less than 0.05). However, no significant differences in total CK activities were detected. Additionally, mitochondrial CK and CK-BB isoenzymes were present in muscle homogenates. A significant correlation was observed in the increase in mean serum total CK (3,322 U/l) and CK-MB (174 U/l) activities 24 h after the race (r = 0.98, P less than 0.05). These results show that gastrocnemius muscle adapts to long-distance training and racing with increased CK-MB activities and imply that skeletal muscle is the major source of elevated serum CK-MB activities in marathon runners.
mesh_terms: D000222:Adaptation, Physiological; D000328:Adult; D003402:Creatine Kinase / Q000097:blood / Q000378:metabolism*; D006801:Humans; D007527:Isoenzymes; D008297:Male; D009132:Muscles / Q000201:enzymology*; D010806:Physical Education and Training; D010807:Physical Endurance; D012420:Running; D013312:Stress, Physiological / Q000097:blood / Q000201:enzymology*
chemical_list: D007527:Isoenzymes; D003402:Creatine Kinase