Elevated Concentrations of Brain‐type Glycogen Phosphorylase in Renal Cell Carcinoma

We determined tissue concentrations of brain‐type glycogen phosphorylase in normal kidney and renal cell carcinoma by enzyme immunoassay; we also localized it immunohistochemically. Tissue concentration of brain‐type glycogen phosphorylase in the renal cortex (n = 13) was 1430±709 ng/mg protein (mean±standard deviation) and that in the medulla (n = 13) was 1270±635 ng/mg protein. On the other hand, the concentration in renal cell carcinoma (n = 26) was 2530±1540 ng/mg protein, ranging from 520 to 6860 ng/mg, significantly higher than those in renal cortex and medulla. Clear cell type tumors contained slightly higher levels of the phosphorylase (2600±1430 ng/mg protein) than granular cell type tumors (2100±1520 ng/mg protein). In renal tissues, brain‐type glycogen phosphorylase was immunohistochemically localized in epithelial cells of proximal and distal tubules, collecting tubules, thick and thin limbs of loops of Henle, and Bowman's capsules. In renal cell carcinoma, the phosphorylase was immnnohistochemically demonstrated in 97% (34/35) of cases, including one sarcomatoid variant. These findings indicate that renal cell carcinoma cells contain enhanced tissue levels of brain‐type glycogen phosphorylase.