Increased activities of MB and BB isozymes of creatine kinase in denervated neonatal and adult rat muscle

Abstract

Creatine kinase (CK) activity and isozyme patterns were assessed in newborn and adult rat anterior tibial muscle in response to denervation. Total CK activity was low in the control neonatal muscle, gradually increasing to the adult level within 1 month. Denervation prevented this normal increase, and, therefore, CK activity was reduced to 25% of control at 2 months. In the denervated adult muscle, total CK activity decreased to 50% of control within 3 weeks and remained at that level. Denervation of neonatal muscle resulted in a greater conservation of MB isozyme compared with controls. The alteration in BB isozyme expression was even more dramatic with a 33-fold difference expressed at 2 months in terms of percent total CK in denervated vs. control muscle. In denervated adult muscle, MB and BB isozyme activities increased gradually, attaining levels 3-fold and 13-fold, respectively, above control muscle at the end of the experimental period.