Identification of receptors for phorbol ester tumor promoters in intact mammalian cells and of an inhibitor of receptor binding in biologic fluids

摘要: Abstract Utilizing [3H]phorbol dibutyrate [P(Bu)2], we have developed an assay for high-affinity phorbol ester receptors in intact rat embryo fibroblasts. At 37 degrees C, binding of [3H]P(Bu)2 reached a maximum within 10 min and was rapidly reversible. The tumor promoters 12-O-tetradecanoyl-phorbol 13-acetate, teleocidin B, mezerein were potent inhibitors binding. Phorbol 4-alpha-phorbol didecanoate, which lack tumor-promoting activity, did not inhibit Epidermal growth factor, platelet-derived fibroblast arginine lysine vasopressin, luteinizing-hormone releasing hormone, diazepam A Scatchard analysis compatible with two classes sites, one Kd = 8 nM about 1--2 x 10(5) sites per cell the other 710 3 10(6) cell. Sera from various species, human amniotic fluid, certain tissue extracts inhibited specific [3H]P(Bu)2. Fractionation serum led to 135-fold purification inhibitory factor molecular weight range 40,000 80,000.