Specific developmental profiles of lysosomal and brush border enzymuria in the human

Various enzymatic urinary activities have been proposed to assess renal proximal tubule damage in children, including neonates. Nevertheless comprehensive knowledge on the developmental aspects of physiological enzymuria is limited, particularly with regard to lysosomal and brush border enzymuria. Urinary activities of two lysosomal enzymes, N-acetyl-beta-D-glucosaminidase (NAG) and beta-galactosidase (GAL), and of two brush border enzymes, alanine aminopeptidase (AAG) and gamma-glutamyltransferase (GGT) were comparatively investigated in normal prematures (n = 28), term neonates (n = 52), infants aged less than 2 years (n = 19) and children (n = 33), and compared to urinary excretion of beta 2-microglobulin (B2M). Enzymatic activities were assayed using either spectrophotometrical (NAG, AAP, GGT) fluorimetrical (GAL) or radioimmunological (B2M) methods, and were related to urinary creatinine excretion. Developmental profiles of both the studied lysosomal enzymes and of B2M were similarly characterized with significantly decreasing values from prematures (NAG 9.29 +/- 1.44, GAL 2.26 +/- 0.26 IU/mmol creatinine, indicated as mean +/- SEM) to term neonates (6,94 +/- 0.58 and 1.76 +/- 0.15 IU/mmol creatinine, respectively) and older infants and children. Lysosomal enzymatic urinary activities correlated linearly with a coefficient of r = 0.75, (p < 0.05), while correlations between each lysosomal enzymatic activity and B2M urinary excretion were weaker.(ABSTRACT TRUNCATED AT 250 WORDS)