Progestin-binding protein in human benign prostatic hypertrophy.

Abstract

Cytosols from human benign prostatic hypertrophy contained progestin-binding components which bound to R 5020, ORG 2058 andprogesterone in a high affinity fashion.Most of the protein bound to R 5020 was recovered in the precipitate with 0-30% saturation of ammonium sulfate. The R 5020-binding protein showed sedimentation coefficients of 3.6 S and 8.4 S, and was eluted in the void volume of a Sephadex G-200 column. This protein was clearly distinguished from the dihydrotestosterone-binding protein by its precipitability by ammonium sulfate, heat stability and susceptibility to delipidization. R 5020 and ORG 2058 binding were markedly inhibited by the addition of R 1881, therefore, most ofthe binding to progestin in cytosols from the benign prostatic hypertrophy seems to be also the sites for R 1881. Although nuclear extract by 0.4 M KC1 showed R 1881 binding, the extract did not contain the R 5020-binding protein, and this suggestedthat the progestin-binding protein observed in the cytosols does not seem to be the steroid receptor.

Histochemical Observation of R1881–Binding Protein in Human Prostatic Cancer

“…This will explain the requirement of a higher concentration of the ligand for suitable staining of tissues when compared with the concentration for satura tion of the binding with free ligand. The nature of the progestin-binding protein in the human prostate is still unclear [17], However, this protein was located in the epithelial cells as was shown in the present study as well as in a previous report [11],…”

Characteristics of Progestin Binder in Hypertrophic Human Prostate.

“…The binder has a similar Kd (dissociation constant) and sedimentation coefficient on sucrose gradient centrifugation to those of the progesterone receptor in the human uterine endometrium (Robel et al, 1981) and in the breast cancer (Horwitz et al, 1985), therefore, the binder in the human prostate has been assumed to be the progesterone receptor per se (Gustafsson et al, 1978, Ekman et al, 1982, Bashirelahi et al, 1983, Schneider et al, 1984. Previous reports from this laboratory, however, have claimed that the progestin binder from the benign hypertrophic human prostate is not the same of the progesterone receptor observed in the female organs, since nuclear extract of the prostatic tissues does not contain a similar binder (Kodama et al, 1981), and the cytosolic binder linked to RU 27987 (a specific ligand for the nuclear progesterone receptor) is not retained on DNA Sepharose (Akimoto et al, 1986). Moreover, the nuclear extract from the hypertrophic human prostate does not contain any component bound to RU 27987.…”