Zonal and age-related difference in the amounts of creatine kinase subunits in cartilage

Energy metabolism in cartilage may affect the morphogenetic events of skeletal growth. Investigating enzymes responsible for energy metabolism in cartilage, such as creatine kinase (CK), can provide clues to an understanding of pathogenesis and treatment of osteochondrodysplasias. In this study levels of CK subunits M (muscle type) and B (brain type) were measured by a highly sensitive enzyme immunoassay system in growth and resting cartilages of the rat rib at various ages. CK-M was predominant, but there was no statistically significant difference in its quantity of CK among cartilages of various ages or between resting and growth cartilage. In contrast, although CK-B levels were low, they showed a significant decrease with advancing age and a significant increase in growth cartilage as compared with resting cartilage. The results of this study suggest that CK in cartilage, especially CK-B, may play an important role in skeletal growth.