Isoenzyme A and Urinary N-Acetyl-beta-D-Glucosaminidase Activity in Normal Pregnancy

Objectives: Urinary N-acetyl-beta-d-glucosaminidase (NAG) activity has been found to increase during normal uncomplicated pregnancy and such behavior could limit the diagnostic value of this enzyme for detection of subclinical tubular injury. The aim of this study was to evaluate urinary NAG activity and isoenzyme A in normal pregnant women at 30th week of pregnancy and in healthy women, to discriminate between physiological and lesional enzymuria. Design and methods: Enzyme activities in first morning fasting urine samples from 20 nonpregnant control and 20 normal pregnant women at 30th gestational week were evaluated by fluorometric methods. Results: Both total and isoenzyme A activity was significantly higher ( p < 0.01) in urines of normal pregnant women compared with control urines, whereas ratio between these two parameters was significantly lower ( p < 0.001). Conclusions: The increase of urinary NAG activity during normal uncomplicated pregnancy appears to be characterized by a prevalent increase in isoenzyme A form, a finding associated with functional (not lesional) enzymuria. The fluorometric assays may represent a simple and rapid method to evaluate whether increase in urinary NAG activity represents a renal physiological adaptation during pregnancy.