A rapid, sensitive assay for analyzing defects in metabolism of steroids in normal and diseased human tissues.

In this report, we describe a simple, rapid biopsy-steroid metabolism assay that is applicable to any steroid tissue system. It consists of mincing the sample, tissue culture incubation, extraction of the steroids and their metabolites from the tissue, and fractionation of the metabolites by high-pressure liquid chromatography (HPLC). Radioimmunoassay is used to verify the elution patterns of certain steroids. Studies of the metabolism of [3H]progesterone in the avian oviduct showed the generation of metabolites that eluted from the HPLC system in a pattern similar to androgens, estrogens, and glucocorticoids. Studies of the metabolism of [3H]testosterone in the human foreskin showed the production of metabolites that eluted from the HPLC system similar to 5 alpha-dihydrotestosterone and 5 alpha-androstane-3,17-dione (androstanedione) from the parent [3H]testosterone. In the production of the metabolite that eluted as androstanedione in samples of foreskin from normal subjects, a significant (P less than 0.001) correlation was found with the age of the donor. Preliminary studies of patients with hypospadias showed a significant (P less than 0.005) decrease in the production of "androstanedione" compared with that in normal subjects. Because of the wide range in rates of metabolism of testosterone in the patients with hypospadias, the effect of age does not seem to be the sole determinant of a low rate of metabolism in these patients. Some samples of hypospadias foreskin had a decreased rate of production of a metabolite that eluted as dihydrotestosterone in comparison with normal foreskin, even when the age of the donor was considered. The assay described herein should be applicable to any surgical biopsy specimen and to all steroids.(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelationships of isoacceptor phenylalanine tRNA species of Rhodopseudomonas sphaeroides.

The phenylalanine tRNA of Rhodopseudomonas sphaeroides was fractionated on benzoylated diethylaminoethyl-cellulose into four isoaccepting species (tRNAPheI to IV). tRNAPheIII represented 80% of the total tRNAPhe in anaerobic, photosynthetically grown organisms, whereas in cultures grown aerobically for prolonged periods, tRNAPheII represented 80% of the total. In cultures adapting to aerobic growth, the addition of rifampin resulted in a tRNAPhe profile characteristic of anaerobic-photosynthetic conditions due to the conversion of tRNAPheII to tRNAPheIII. In fully adapted aerobic cultures, this conversion was inhibited in the presence of chloramphenicol or rifampin. The conversion of tRNAPheIII to tRNAPheII was not observable in vivo. It is proposed that an enzymic activity synthesized during anaerobic-photosynthetic growth was responsible for the conversion.

Evidence for an androgen receptor in human testis.

The present study identified and characterized an androgen-binding protein in human testicular tissue. Human testes were homogenized in dilute Tris buffer containing thioglycerol, phenylmethylsulfonylfluoride, and molybdate. The supernatant (termed cytosol) was incubated with radiolabeled androgen methyltrienolone (tritium-labeled R1881), and nonspecific binding was determined by adding 100-fold excess of unlabeled R1881 together with [3H]R1881 to cytosol. Specific binding with saturation at 24 hours was observed. Scatchard analysis of the specific binding with the use of increasing concentrations of [3H]R1881 alone and [3H]R1881 plus 200-fold excess unlabeled R1881 demonstrated a high-affinity (dissociation constant = 2.18 X 10(-10) mol/L), low-capacity (2924 molecules per cell) class of binding sites. A second class of lower-affinity sites was identified with a dissociation constant equaling 1.2 X 10(-8) and 26,300 molecules per cell. The bulk of the higher-affinity class of sites was precipitated at 35% ammonium sulfate. In competitive binding assays, dihydrotestosterone and testosterone greatly diminished binding to this high-affinity class of sites. Progesterone also diminished binding but to a lesser degree. Estradiol, estriol, and estrone failed to compete for these sites. Analysis of the receptor, using sucrose gradients, revealed a major peak in the 4S region and a small peak at 8S. A similar high-affinity (dissociation constant = 4.28 X 10(-9), low-capacity (4860 molecules per cell) binding protein was identified in purified nuclei. Binding to nuclear chromatin was demonstrated in the cell-free binding assay, and nuclear binding was further illustrated in the biopsy assay of intact tissue, suggesting translocation in vivo. These properties are characteristic of the androgen receptor and suggest that human testis is a target tissue for androgen, as has been found in animal tissue.

Evidence for an androgen receptor in the human placenta.

A steroid-binding protein was examined in human placental and nuclei which had several characteristics of an androgen receptor. It binds R 1881 (methyltrienolone), a steroid specific for androgen receptors, with high affinity (dissociation constant equals 1.3 to 50 nM) and low capacity (n equals 1.2 to 21 moles/mg of protein). The steroid-binding protein is found in the nuclei as well as the cytosol of the placenta but is not found in either the cytosol or the nuclei of fetal membranes; thus, it is tissue-specific. Among the natural steroids, 5 alpha-dihydrotestosterone competes most efficiently with R1881 for binding to the protein. Testosterone is the next best competitor. When the ranges of dissociation constants and concentrations of binding sites for placentas of various gestational periods are compared, not significant differences are observed between period of gestation and magnitude of binding constants.

Absence of high-affinity binding of progesterone (R 5020) in human placenta and fetal membranes.

Increased levels of maternal serum progesterone occur during the last stages of human gestation. The function of the high level of this steroid is unknown. The presence of a progesterone receptor in the placenta was investigated to determine whether progesterone action on the placenta might serve as one function of the high level of this steroid. Cytosol and nuclear fractions, derived from human placentae and fetal membranes, were examined for the presence of progesterone receptors by conducting exchange assays, using tritiated R 5020 (17,21-dimethyl-19-norpregna-4,9-diene-3,20-dione) as the radiolabelled ligand. High-affinity, low-capacity binding, characteristic of steroid receptors, was estimated as the difference between binding of radiolabelled ligand in the presence of no unlabelled ligand and that in the presence of a 100-fold excess of unlabelled ligand. These exchange assays were conducted during a 24-hour period at 0 degrees C, to allow maximal stability of the receptor, and during a 3-hour period at 20 degrees C, to allow the rapid exchange of radiolabelled ligand for any bound endogenous progesterone. The assays of all fractions showed no specific binding of the R 5020, thus indicating the absence of progesterone receptors in the cytosol and nuclei of the human placenta and the fetal membranes.

The androgen receptor in normal human foreskin. I. Stabilization and identification of two receptor subunits.

Use of glycerol and the protease inhibitor phenylmethylsulfonyl fluoride resulted in a fourfold increase in the yield of androgen receptor from human neonatal foreskin and a tenfold increase in stability of this receptor. The general physical properties of the androgen-binding component isolated from the cytosol of human neonatal foreskin were found to be consistent with those previously reported for androgen receptors. The synthetic androgen methyltrienolone (R1881) was bound with high affinity (a mean dissociation constant of 0.51 nmol/L) and low capacity (5.6 fmol/mg of protein); maximum binding required 4 hours. Affinity of the receptor was highest for R1881 followed by dihydrotestosterone, testosterone, and progesterone. 17 beta-Estradiol showed little or no competition. The receptor exhibited a change of sedimentation coefficient from 8S to 4S upon treatment with 0.1 mol/L potassium chloride. Isoelectric focusing demonstrated the existence of two molecular species with apparent isoelectric points of 7.2 and 5.7.

Androgen receptor in human foreskin. II. Characterization of the receptor from hypospadiac tissue.

Hypospadias represents a spectrum of disorders known as androgen insensitivity syndromes, which are characterized by a nonresponsiveness of an androgen target tissue to the steroid. The basic defect in this disorder is unknown. This article presents results of studies of the androgen receptor with use of human foreskin from normal neonates undergoing circumcision and from patients undergoing urethroplasty necessitated by hypospadias. It is speculated that a defect in receptor level or function might explain this disorder. The androgen receptors from both normal and hypospadiac tissue were stabilized with a buffer containing 50 mM Tris hydrochloride, 1 mM ethylenediaminetetraacetic acid, 12 mM monothioglycerol, 10% (v/v) glycerol, and 10 mM sodium molybdate plus 1 mM phenylmethylsulfonylfluoride (pH 7.5). The receptors were characterized by Scatchard analysis, competitive binding assays, sedimentation analysis, molecular sieve chromatography, and isoelectric focusing techniques. Specific R 1881 binding to soluble proteins from normal human foreskin was shown to be high affinity (dissociation constant = 0.5 nM), low capacity (6 fmol/mg of protein), and steroid specific. Sedimentation analysis by sucrose density gradients demonstrated the 8S-to-4S shift from low- to high-salt treatments. The receptor from the foreskins of hypospadiac patients also contained androgen receptor in a concentration similar to that in the foreskins of normal persons. The affinity for steroid binding and sedimentation profiles or sucrose gradients of the androgen receptor between normal persons and hypospadiac patients were also similar. However, the androgen receptor from hypospadiac patients displayed different patterns of molecular sieve chromatography from those displayed by the receptor of normal persons. The reason for this difference is not known but may reflect a defective receptor and explain the basic mechanism of this disorder.