[Creatine kinase and creatine isoenzyme activities in newborn. Development of the organ-typical isoenzyme pattern during the fetal period (author's transl)].

The activity of the creatine kinase isoenzyme was measured in the serum of 133 healthy newborn. In contrast to the conditions in the adult, a normal range of 0-45 U/1 was found. No creatine kinase BMB activities were established. The increased creatine kinase-MB activities in newborn could be explained by means of an examination of the creatine kinase isoenzyme pattern in the skeleton muscle of foetuses and newborn. Depending upon the gestation age, creatine kinase-MB activity levels were found amounting to as much as a multiple of ten of the adult levels. Due to the deviation of the creatine kinase isoenzyme distribution in the organ tissue of newborn, identified in this study for the first time, creatine kinase-MB activity seems to be unsuitable as an indicator of myocardial damage during the neonatal period.