Regulation of ovarian 17β-hydroxysteroid dehydrogenase activity by gonadotropin

Serum testosterone levels are elevated prior to the lutropin surge, and decline abruptly following the release of endogenous lutropin. To investigate this phenomenon, the activity of 17β-hydroxysteroid dehydrogenase, the enzyme directly related to testosterone production form androstenedione, was measured. This was done in immature rats in which follicular maturation and ovulation were induced by pregnant mare serum gonadotropin administration. It appears that the effect of the gonadotropin on the enzyme activity is sharply divided into two phases that match with the follicular and the luteal phases. One day following gonadotropin administration, there was already a 7.67-fold increase in the original activity which further increased 48 h following hormone administration. At the peak of the lutropin surge, when follicular development is at its maximum, a 18.44-fold increase was measured. The activity fell abruptly 10 h following ovulation, at a time when fresh corpora lutea are already present in the ovary.It seems that the evaluation of serum testosterone followed by its abrupt decline, is directly related to the increased and decreased ovarian 17β-hydroxysteroid dehydrogenase activity. The possible importance of the observed changes to the mechanisms of the onset of puberty are discussed.     

Reduction of testicular luteinizing hormone/human chorionic gonadotropin receptors by [D-Trp6]-luteinizing hormone releasing hormone in hypophysectomized rats.

Adult and immature male rats were hypophysectomized and injected daily with saline or 0.2 or 2 μg of superactive Luteinizing Hormone Releasing Hormone (LHRH) agonist, [D-Trp⁶]-LHRH subcutaneously for seven days - with, or without, concomitant treatment of 1 IU Human Chorionic Gonadotropin (hCG) or 50 IU Pregnant Mare Serum. The administration of [D-Trp⁶]-LHRH reduced Luteinizing Hormone/Human Chorionic Gonadotropin receptors in all cases. The magnitude of this reduction was dose-related. As small a dose as 0.2 μg of the peptide resulted in approximately a 72% reduction of the receptors. The results suggest a direct action of [D-Trp⁶]-LHRH on the testis. It also indicated that reduction of testicular Luteinizing Hormone/Human Chorionic Gonadotropin receptors by the peptide is not necessarily due to the over-stimulation of Luteinizing Hormone (LH) release from the pituitary through a “down regulation” mechanism.     

Evaluation of adrenal function in rats by the measurement of urinary free corticosterone, free aldosterone and free 11-deoxycorticosterone.

Methods für the determination of urinary free corticosterone, free aldosterone and free 11-deoxycorticosterone (DOC) in rats are described. The free corticosteroids were measured in urine samples of 0.1–0.5 (2.0) ml by radioimmunoassay after purification by column chromatography. The validity of the methods is demonstrated by the data of the free urinary corticoids under basal conditions and after adrenal suppression and various forms of adrenal stimulation. The basal excretion of free corticosterone, free aldosterone and free DOC was 123.71 ± 15.31 (x? ± SD), 3.87 ± 1.29 and 10.61 ± 2.24 ng/day, respectively, exhibiting a decrease to 26.20 ± 5.21, 1.05 ± 0.47 and 1.35 ± 1.20 ng/day after adrenal suppression by dexamethasone. Irrespective of the mode of adrenal stimulation i.e., synthetic ACTH and systemic (cold, hunger) or neurotrophic (ether, reserpine) stress stimuli free corticosterone increased to about 450 ng/day, while free aldosterone excretion decreased during hunger and cold and was strongly enhanced after the application of reserpine. Furthermore, determination of urinary free DOC, which increased by a factor of 4, may be applied in the metyrapone test. There was a good correlation between the excretion of free corticosterone and that of free aldosterone and free DOC under basal conditions and after ACTH application, demonstrating that ACTH is responsible for the secretion of all the 3 corticoids measured. It is concluded, that the measurement of the urinary excretion of corticosterone, aldosterone and DOC is a valuable parameter of adrenal function in rats. Furthermore, in small laboratory animals like rats steroid measurements in urine are often more advantageous than Measurements in plasma.     

Sertoli cells from immature rats : in vitro stimulation of steroid metabolism by FSH.

Sertoli cells from 10 day old rats convert androstenedione to testosterone and 5α-androstane-3α,17β-diol, testosterone to 17β-hydroxy-5α-androstan-3-one and 5α-androstane-3α,17β-diol, and 17β-hydroxy-5α-androstan-3-one to 5α-andro-stane-3α,17β-diol after 72 hours $\text{in vitro}$. Conversions of androstenedione to testosterone and 5α-androstane-3α,17β-diol, and testosterone to 5α-androstane-3α,17β-diol were 2 to 3 times greater in FSH treated cultures. Steroid conversion was not stimulated significantly by LH or TSH. The results are interpreted as evidence that in young rats Sertoli steroid metabolism is stimulated by FSH, that Sertoli cells are an androgen target and that FSH may induce or facilitate Sertoli androgen responsiveness.     

Synthesis of new steroid haptens for radioimmunoassay. part I. 15β-Carboxyethylmercaptotestosterone-bovine serum albumin conjugate. measurement of testosterone in male plasma without chromatography

A radioimmunoassay (RIA) procedure has been developed for measurement of testosterone in male plasma after ether:chloroform (4:1) extraction of the plasma sample without resorting to chromatography. The highly specific anti-testosterone serum was generated from both rabbits and sheep immunized with 15β-carboxyethylmercapto-testosterone-BSA conjugate. The synthesis of 15β-carboxyethylmercaptotestosterone and the preparation of its BSA conjugate are described. The high affinity (K_a = 2.38 × 10⁹ liters/mole) antiserum binds 50% of 50 picograms of tritiated testosterone at working dilutions of 1:100,000 to 1:200,000. Both 5α and 5β-dihydrotestosterone compounds exhibited less than 2% cross-reaction. The only other steroids that showed minor cross-reaction were 11β-hydroxytestosterone (3.8%), progesterone (2.1%), corticosterone (1.6%), and deoxycorticosterone (7.7%).     

Inbition of steroidogenic response to corticotropin in mouse adrenal tumor cells (Y-1 by the ionophore A23187 Role of protein biosynthesis

Addition of the ionophore A123187 to Y-1 mouse adrenal tumor cells in monolayer culture inhibits steroidogenesis and the steroidogenic response to corticotropin (50% inhibition at 1 · 10^?7 M). inhibition is rapid in onset and is not overcome by addition of external Ca²⁺. The ionophore also inhibits stimulation of steroid synthesis by cyclic AMP. A23187 inhibits incorporation of the amino acid lysine into protein by Y-1 cells and the dose dependence of this inhibition closely resembles that of the inhibition of the steroidogenic response to corticotropin. Addition of A23187 to a subcellular system for protein synthesis prepared from Y-1 cells, inhibits incorporation of the amino acid phenylalanine into protein and this effects and this effect is not overcome by high concentrations of Ca²⁺. The inhibitory effect of A23187 on the response to corticotropin, like that response itself, takes place at some part of steriod synthesis after entry of cholesteriol into the cells and before the side-chain cleavage of cholesterol. These studies confirm the importance of protein synthesis in the response to corticotropin and demonstrate that the effect of protein synthesized under the influence of corticotropin is exerted at some point in the events which bring substrate (cholesterol) to the mitochondrial side-chain cleavage enzyme system. It is also shown that A23187 inhibits protein synthesis, and hence the response to corticotropin, by a mechanism which is independent of the concentration of available Ca²⁺.     

In vitro biosynthesis of radioactive estradiol-17 beta, 17-glucosiduronate by rhesus monkey liver.

A method for the preparation of radioactive estradiol-17 beta, 17-glucosiduronate by incubating 3H-estradiol with rhesus monkey liver microsomal preparation in the presence of uridine diphosphoglucuronic acid is described. Small but significant amounts of the conjugate were also obtained from the 150,00 pellet and cytosol fractions. The addition of NADPH to the incubation media increased the yield of radioactive-estradiol-17 beta, 17-glucosiduronate perhaps by preserving the integrity of the C-17-hydroxyl group. As expected, the effect of the reduced nucleotide was more pronounced in the fractions other than the microsome. The biosynthesized conjugate was isolated and purified by multiple column chromatography and the structure was confirmed by derivative formation, enzyme hydrolysis and crystallization of the aglycone.     

Rat and human embryo and post-natal sera contain a potent endogenous competitor of estrogen-rat alpha-fetoprotein interactions

A highly active inhibitor of the binding of estrone and estradiol-17β to rat alpha-fetoprotein is demonstrated for the first time in embryo, immature and adult rat sera as well as in fetal and adult human sera. The competitive character and the narrow specificity of this inhibition effect is shown. The major compound responsible for this activity is isolated by successive column Sephadex LH₂₀ and thin layer chromatography : it is characterized as a nonpolar, nonphenolic, dialysable and thermostable substance, unreactive towards anti-estrone and anti-estradiol-17β anti-bodies. The possible biological role of an endogenous non-estrogen ligand of rodent fetoproteins is discussed.     

Endometrial stromal cells and decidualized stromal cells: Origins,transformation and functions

Decidualization of endometrium, which is characterized by endometrial stromal cell (ESC) decidualization, vascular reconstruction, immune cell recruitment, and plentiful molecule production, is a crucial step for uterus to become receptive for embryo. When implantation takes place, ESCs surround and directly interact with embryo. Decidualized stromal cells (DSCs) are of great importance in endometrial decidualization, having a broad function in regulating immune activity and vascular remodeling of uterus. DSCs are shown to have a higher metabolic level and looser cytoskeleton than ESCs. What's the origin of ESCs and how ESCs successfully transform into DSCs had puzzled scientists in the last decades. Breakthrough had been achieved recently, and many studies had elucidated some of the characters and functions of DSCs. However, several questions still remain unclear. This paper reviews current understanding of where ESCs come from and how ESCs differentiate into DSCs, summarizes some characters and functions of DSCs, analyzes current studies and their limitations and points out research areas that need further investigation.