Before, and at various time intervals after a marathon race, we examined the changes in serum β -enolase concentration in 6 healthy, non-athlete volunteers and compared then with changes in serum creatine kinase (CK) and creative kinase MB isozyme (CK-MB) activities. The enzyme β-enolase (a β and ββ) exists in skeletal and heart muscle, where it catalyzes the step in the glycolytic pathway between 2-phosphoglycerate and phosphoenolpyruvate. For determination of β-enolase concentration, serum was analyzed by the sandwich enzyme immunoassay method. The β-enolase concentration was significantly increased from the pre-race value. At 6 h after the race, the β-enolase concentration became maximal in all subjects, while CK and CK-MB activities did so in one and two subjects, respectively. CK and CK-MB activities peaked at 24 h in five and four subjects, respectively. The rise and fall of β-enolase concentration was faster than those of CK and CK-MB activities. Therefore, assay of β-enolase concentration has considerable advantage for early detection of skeletal muscle damage and is highly specific and sensitive. The mean β-enolase concentration±S. D. before and immediately after, and 6, 24, 48 h and 1 week after the race was 7.7±5.96, 204±87.6, 400±292.0, 214±166.3, 41.1±30.89, and 6.5±2.20 ng/ml, respectively. There was a significant correlation between the peak β-enolase concentration and peak CK activity (r=0.981, p<0.05) and peak CK-MB activity (r=0.926, p<0.05) . However, there was no significant correlation between β-enolase concentration and Vo₂max.
These results suggest that serum β-enolase concentration may be a more effective marker of skeletal muscle damage after prolonged exercise, as well as for determination of CK activity.