Enolase isozymes in renal tubules and renal cell carcinoma

To elucidate the localization of enolase isozymes in renal tubules and renal cell carcinoma, an immunohistochemical study and quantitative analysis by employing the enzyme immunoassay were performed. The alpha-enolase was localized in almost all epithelial cells of renal tubules except for loops of Henle. The gamma-enolase was localized in macula densa cells and epithelial cells of loops of Henle and collecting ducts of the medulla, but not in those of proximal tubules. In renal cell carcinoma, most tumor cells possessed two enolase isozymes. From these immunohistochemical findings, it is suggested that enolases are present mainly in the alpha alpha form in epithelial cells of proximal tubules, in the gamma gamma form in those of loops of Henle, and in the two forms and/or the alpha gamma form in tumor cells of renal cell carcinoma. The levels of gamma-enolase in the normal cortex were 16.8 +/- 3.7 ng/mg protein (n = 7), whereas those in renal cell carcinoma were 928 +/- 554 ng/mg protein (n = 7), about 55-fold higher than those in the normal cortex. The serum gamma-enolase levels were also enhanced in 20 (49%) of 41 patients with renal cell carcinoma. Because it is generally accepted that renal cell carcinoma is derived from epithelium of proximal tubules, the expression of gamma-enolase has occurred during carcinogenesis.