Abstract
Based on the potential progestin sensitivity of the growth of human renal cell carcinoma, tumour tissue from 88 patients was analysed for progestin receptors. With the dextran-coated charcoal assay, cytoplasmic components which bound the potent progestin R 5020 specifically and with high affinity could be detected in 42% of the carcinomas. The apparent dissociation constant of the R-5020-binder complex amounted to 3.1 ± 1.2 × 10––8 mol/l. Sedimentation in sucrose gradients revealed the bulk of these components to be in the 4-S region. The ligand specificity for binding to these sites indicated a requirement for progestins. Despite the enormous case material investigated, we were unable to confirm the presence of the high receptor concentrations reported in the literature.