title: Involvement of the prostatic steroid-binding protein in the transfer of ligand to the dioxin receptor.
abstract: The prostatic steroid-binding protein (PSP) represents a highly abundant protein in the rat prostate which binds carcinogens reversibly and with high affinity. The biological role of PSP and the toxicological implications of the carcinogen-protein interaction are unclear. In this report, we have attempted to examine a possible role of PSP in the transfer of ligands to the dioxin receptor. PSP was purified from the rat ventral prostate and labeled in vitro with 2,3,7,8-[3H]tetrachlorodibenzo-p-dioxin (dioxin). Dioxin-labeled PSP was then incubated with rat liver cytosol in the presence or absence of a 200-fold excess of nonradioactive competitor, 2,3,7,8-tetrachlorodibenzofuran. After 2 h of incubation, a complete in vitro transfer of ligand from PSP to the rat hepatic dioxin receptor was observed, as assessed by velocity sedimentation analysis of specific dioxin binding. These results indicate that a high abundance carcinogen-binding protein, such as PSP, may be of importance in the cellular transfer of dioxin receptor ligands, thereby eliciting a receptor-mediated biochemical and/or toxic response.
mesh_terms: D000727:Androgen-Binding Protein / Q000502:physiology*; D000818:Animals; D001692:Biological Transport; D004147:Dioxins / Q000378:metabolism*; D066298:In Vitro Techniques; D008024:Ligands; D008297:Male; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism*; D060789:Prostatein; D051381:Rats; D011919:Rats, Inbred Strains; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug / Q000378:metabolism*; D060765:Secretoglobins; D014598:Uteroglobin; D060788:Mammaglobin B
chemical_list: D000727:Androgen-Binding Protein; D004147:Dioxins; D008024:Ligands; D000072317:Polychlorinated Dibenzodioxins; D060789:Prostatein; D018336:Receptors, Aryl Hydrocarbon; D011955:Receptors, Drug; D060765:Secretoglobins; D014598:Uteroglobin; C511484:Scgb1d2 protein, rat; C511483:Scgb1d4 protein, rat; C556468:Scgb2a1 protein, rat; D060788:Mammaglobin B