CLINICALCHEMISTRY,Vol.28,No.2,1982 317 CreatineKinaselsoenzymesin Serum from CordBloodandthe Bloodof

transferase; EC 2.7.3.2; CK) were measured by electra-phoresisin serum from cord blood and skin-puncture blood taken from 45 healthy full-term infants during the first three postnatal days. Mean total CK activities (in U/L at 30 #{176}C) were 185 in cord samples, 536 in samples taken between 5-8 h postnatally, 494 between 24-33 h, and 288 in the 72-100 h samples. Values for all three isoenzymes in-creased to a peak over this period, with the highest values generally being found in the samples taken 5-33 h after birth; the subsequent decline was most rapid for CK-BB. Serum CK isoenzymes in cord samples and those taken at 72-100 h in the 11 babies delivered by cesarian section did not differ significantly from those of babies delivered vaginally. However the postnatal increases in total CK, CK-MM, and CK-MB (but not in CK-BB) were significantl