Urinary N-acetyl-beta-D-glucosaminidase (NAG) isoenzyme profiles: a tool for evaluating nephrotoxicity of aminoglycosides and cephalosporins.

The study of urinary NAG isoenzymes in different nephrotoxic states shows that each antibiotic is characterised by a specific isoenzyme profile which probably reflects the very nature of its toxic mechanism. Those aminoglycosides which are responsible for important elimination of B- and I-forms would directly induce the synthesis of these isoenzymes in the endoplasmic reticulum. Cephalosporins, which are less nephrotoxic, present profiles which are closer to those obtained for normal urine. A combination aminoglycoside plus cephalosporin, though globally more nephrotoxic than aminoglycosides alone, is characterised by relatively poorer profiles of B- and I-forms. This could be linked to the reciprocal interaction of one antibiotic with the toxic mechanisms of the other.