IMMUNOGOLD ANALYSIS OF ANTIOXIDANT ENZYMES IN HUMAN RENAL-CELL CARCINOMA

Analysis of activities of the antioxidant enzyme manganese superoxide dismutase in human renal cell carcinomas often showed greatly altered enzyme levels (either elevated or depressed) compared to the cell of o rigin, the kidney proximal tubule. In order to better understand the v ariability observed, immunogold studies were performed on human renal cell carcinomas using a polyclonal antibody to human kidney manganese superoxide dismutase. For comparison, studies were also performed usin g antibodies to other antioxidant enzymes. For histologic studies, ren al cell carcinomas were subclassified on the basis of light microscopy and ultrastructural analysis into clear cell, granular cell, or mixed clear and granular cell variants. In all three types of tumor, immuno gold studies showed little staining using antibodies to copper, zinc s uperoxide dismutase or glutathione-dependent enzymes. However, intensi ty of labelling for manganese superoxide dismutase and catalase depend ed on the cell type(s) in the tumor. Clear cell variants demonstrated trace staining for manganese superoxide dismutase and catalase, while granular cell variants exhibited heavy staining for both of these enzy mes. Mixed types of tumors showed clear cells with trace staining for all antioxidant enzymes examined, while granular cells again showed in tense labelling for manganese superoxide dismutase and catalase. Using normal kidney proximal tubule as a comparison, immunogold ultrastruct ural analysis using antibody to manganese superoxide dismutase demonst rated infrequent small lightly labelled mitochondria in clear cell var iants, while granular cell variants exhibited numerous medium-sized he avily labelled mitochondria. These data suggest that: 1) the variabili ty in activity values for manganese superoxide dismutase may be due to heterogeneity of cell types in these tumors and 2) manganese superoxi de dismutase immunoreactive protein was elevated in granular cells bot h because of an increase in number of mitochondria and because the lab elling density in mitochondria was increased compared to mitochondria in clear cell types or in normal proximal tubular cells.