URINARY TREHALASE ACTIVITY IS A USEFUL MARKER OF RENAL PROXIMAL TUBULAR DAMAGE IN NEWBORN-INFANTS

To clarify the reliability of urinary trehalase activity as a marker o f cellular proliferation and/or damage of renal proximal tubules, the activity was examined in healthy newborn infants or infants treated wi th tobramycin, a drug known as causing tubular cell damage. Eighty-one newborn infants (56 mature infants and 25 premature infants) were enr olled in the study. Urinary trehalase was examined using a spot urine sample during the first 7 days of age and on the 10th day of age. A go od positive correlation was observed between urinary trehalase activit y/creatinine ratio (T/Cr) on the 10th day of age and conceptional age or body weight (n = 46, r = 0.58, p < 0.001). Urinary trehalase of 29 healthy mature infants was higher during the first few days of age, af ter which it decreased to an almost steady level. Urinary trehalase of 6 premature infants during the first few days of age was significantl y lower than that of mature infants, after which it increased and beca me equal to that of the mature infants on the 7th day of age. Treatmen t with ampicillin (100 mg/kg) and tobramycin (5 mg/kg) of 6 mature inf ants with pneumonia for 6 days resulted in a significant elevation of the urinary T/Cr. The extent of this elevation was greater than that o f the urinary N-acetyl-beta-D-glucosaminidase (NAG) activity/creatinin e ratio (NAG/Cr). A significant correlation was observed between the u rinary T/Cr and the urinary NAG/Cr (r = 0.67, p < 0.01) or gamma-gluta myl transpeptidase/creatinine ratio (r = 0.48, p < 0.01). These observ ations indicate that urinary trehalase activity may be a useful marker of cellular proliferation and/or damage of renal proximal tubules in newborn infants.