1607 URINARY PROTEIN EXCRETION IN EARLY INFANCY

Total protein excretion rates (PER) and urinary protein patterns have been studied in 67 newborns with gestational age (GA) ranging from 25 to 40 weeks. Timed sequential urine collections were obtained from infants up to two months of age. In infants 1 week of age. Similarly, in infants > 38 weeks GA PER's fell from 43.6±28.0 μg/min (n=7) at 1 week of age. A significant positive correlation of GA to the PER was noted on Day 1 (r2=0.75; p 1 week (r2=0.45; p 38 weeks GA had significantly higher PER's as compared to infants Of comparable post-natal age, but lesser GA. The pattern of urinary protein excretion was evaluated, by SDS polyacrylamide gel electrophoresis. Results of this evaluation indicate qualitative as well as quantitative differences in protein excretion by the newborn at various GA's and post-natal ages. In particular certain low MW fractions are found in urines at an early post-natal age which are not found in the urine of the same infants at a later age. These data suggest that proteinuria of the early newborn period may be in part consequent to decreased proximal tubular reabsorption of low molecular weight proteins.