Urinary N-acetyl-beta-D-glucosaminidase activity in healthy, polycythemic and hypoxic neonates.

The authors investigated the urinary N-acetyl-beta-D-glucosaminidase (NAG) activity in the case of 101 normal healthy and 20 polycythemic newborns and prematures, and 50 prematures suffering from hypoxia on the 1st, 2nd, 4th, 14th, and 28th day after birth. The obtained activities were referred to the creatinine concentrations of the urine samples and given as NAG index. There were no significant differences in the NAG indices either between fullterm and preterm babies or between appropriate for gestational age (AGA) and small for gestational age (SGA) neonates of the normal group. The NAG indices on the first day of life were significantly higher in the case of polycythemic newborn in comparison with the normal group (p less than 0.01). On the 14th day, after the partial plasma exchange, the NAG indices returned to the normal range. The premature babies suffering from IRDS received an average 10.1 days oxygen supplementation. Their NAG indices were significantly (p less than 0.01) higher on the 1st, 2nd, 4th days than those of the healthy prematures of the normal group and decreased considerably up to the 14th day. Finally the NAG indices reached the normal value on the 28th day. These results support the assumption that the urinary NAG index is a suitable indicator of the renal tubular damage during the newborn period.