In vitro and in vivo enhancement of progesterone binding to the uterine progesterone receptor by cortisol

Androgen, estrogen, and progesterone receptor contents and serum hormone profiles in patients with benign hypertrophy and carcinoma of the prostate

Cytosolic and nuclear androgen, estrogen and progesterone receptor content was measured in the groups of 11 prostatic carcinoma (PCA) and 32 benign prostatic hypertrophy (BPH) samples. All BPH cases were positive for the cytosolic progesterone (PRc) and estrogen receptor (ERc), whereas only 85% of cases (23/27) contained the androgen receptor (ARc). Only those five patients who received estrogen treatment in the PCA group had detectable ARc. PRc was present in all of the PCA cases, whereas ERc could be detected in only 82% (9/11) of cases. Cytosolic contents of all three steroid receptors, however, were higher in the PCA group. The level of nuclear steroid receptors, although present in fewer cases in both groups, was higher than the cytoplasmic receptors. The serum profile of estradiol, cortisol, and prolactin was normal in both groups, whereas LH, FSH, and progesterone levels were higher than in normal adults. Serum testosterone level was within normal range in the BPH group, but it was significantly below normal (P less than 0.005) in PCA patients.

Assay and characterization of ovarian testosterone receptor

Ovarian cytosol from immature, hypophysectomized rats was used to characterize the biochemical properties of ovarian androgen receptor and to develop a reliable and convenient assay procedure for its measurement in small quantities of tissue. The results show that Sephadex G-25 columns provide a rapid and reliable method to separate bound from free testosterone for assay of androgen receptor in the ovarian tissue. The binding affinity (KD = 0.6 nM) and sedimentation value (8S) for the ovarian androgen receptor are similar to other steroid receptors and is saturable. It is inactivated by heat and protease digestion and the binding is specific for potent androgens. The ovary contains approximately equal quantities of androgen and estrogen receptor. A physiological role for the presence of androgen receptor in the ovarian tissue is proposed.

Effects of progestins on the progesterone receptor in guinea pig uterus

We examined the effects of progesterone and some synthetic progestins and other steroids on the physical properties of the progesterone receptor of guinea pig uterine cytosol and on the binding of the receptor by nuclei. Progestational potency seemed to correlate with the ability to keep the receptor in the 7S form and to prevent dissociation into smaller subunits. The rate of activation prior to nuclear binding was slower with steroids of increasing progestational activity. Therefore activation in vitro may be unrelated to biological activity. Concentration of the cytosol led to a decrease in the equilibrium association constant. The extent of the decrease was less with progesterone than with its metabolite, 5 alpha-pregnanedione. When cytosol and nuclei were incubated in the absence of ligand measureable progesterone receptor was bound by the nuclei. The uncomplexed nuclear receptor bound [3H]-progesterone of [3H]-R5020 rapidly at 0 degrees, but progesterone-receptor complexes exchanged [3H]-progestin slowly at 0 degrees. Progesterone increased the amount of nuclear receptor at concentrations of 10(-9) and 10(-8)M, but decreased binding at higher concentrations. 5 alpha-Pregnanedione had the same effect as progesterone, but other metabolites of progesterone that had little affinity for the 7S progesterone receptor in cytosol had no effect on nuclear binding at any concentration. Glucocorticoids, testosterone and estradiol-17 beta increased the nuclear binding of the progesterone receptor when present at concentration of 10(-8)M and greater.

Uterine and lung uteroglobins in the rabbit. Two similar proteins with differential hormonal regulation

Previous studies have shown that several rabbit tissues contain proteins which cross-react in the radioimmunoassay for uteroglobin, a progestin-regulated protein in rabbit uterus (Torkkeli et al. (1977) Mol. Cell. Endocrinol. 9, 101-118). In the present study, a uteroglobin-like protein was purified to an apparent homogeneity from an extra-uterine tissue, rabbit lung, by successive chromatographies on hydroxyapatite, Sephadex G-75, SP-Sephadex, DEAE-cellulose and CM-cellulose. The final preparation behaved homogeneously in various polyacrylamide gel electrophoretic systems and in isoelectric focusing. The uteroglobin-like protein isolated from the lung had very similar physicochemical and immunological properties to those of uteroglobin present in the rabbit uterine fluid. The two proteins had: (i) the same molecular weight, of approx. 13 000, with a two subunit structure (each approx. Mr 7000); (ii) identical behavior in polyacrylamide gel electrophoresis under non-denaturing and denaturing conditions; (iii) the same isoelectric point at pH 5.4; (iv) absence of carbohydrate in the molecule; (v) very similar amino acid compositions; (vi) lack of tryptophan among the amino acids; (vii) the same N-terminal amino acid (glycine), and (viii) indistinguishable immunological characteristics. Collectively, these data strongly suggest that uterine and lung uteroglobins are identical proteins. In contrast to the induction of the uterine uteroglobin by steroids with progestational activity, the synthesis of extra-uterine uteroglobins was no affected by these steroid hormones to any major extent. In keeping with the concept that lung is a target tissue for glucocorticoid action, cortisol and dexamethasone were capable of increasing the concentration of lung uteroglobin 3-fold (from 3 to 9 microgram/mg soluble protein). These compounds did not, however, alter the secretion of the uterine protein. Administration of high doses of testosterone and 5alpha-dihydrotestosterone elevated significantly the content of both uterine and lung uteroglobin. Only approx. one-fifth of the adult pulmonary uteroglobin levels were present in lungs of newborn rabbits indicating that developmental changes occur in the lung uteroglobin content.

Further consideration of systematic errors present in protein-ligand interactions

Relatively minor systematic errors present during measurements of protein-ligand interaction can lead to large inaccuracies in the calculated values of the equilibrium dissociation constant and the total concentration of the binding protein. These errors, which include binding of the ligand to low affinity material and underestimation of bound ligand, cause the calculation of the concentration of free ligand at equilibrium to be overestimated. We report herein a model of ligand-protein binding which incorporates these errors into the mathematical formulation of the equilibrium binding equation. The effect of these errors on the Scatchard plot is presented.