Enzyme histochemistry in plastic-embedded sections of normal and diseased kidneys

Interest in the role of mononuclear phagocytes in glomerulonephritis (GN) and in defining markers of renal neoplasms led the authors to study alpha-naphthyl acetate/butyrate esterase (ANAE/ANBE), alkaline phosphatase (AlkP), acid phosphatase (AcP), 5'-nucleotidase (5'N), and ATPase (ATP) activity in paraformaldehyde-fixed, plastic-embedded renal tissue from patients with a variety of pathologic conditions. These conditions included GN, renal tumors, and transplant rejection. Enzymatic staining for ANAE, ANBE, AcP, AlkP, and ATP was generally confined to tubules and collecting ducts in normal kidney. Nine of 10 cases of renal carcinoma had weakly to strongly positive reactions with AlkP, AcP, and ANAE; 9 of 10 cases of Wilms' tumor showed weakly positive reactions with AcP and ANAE, particularly in tubular structures. Severely damaged kidney allografts showed surprising retention of normal histochemical features. In all cases 5'N stained both glomerular capillaries and interstitial vasculature; ATPase and AlkP stained interstitial vessels only. Plastic embedding provides superb preservation of both microscopic anatomy and enzymatic activity, which may allow utilization of enzyme histochemistry for diagnostic and research purposes.