More about X-linked testicular feminization of the mouse as a noninducible(is)mutation of a regulatory locus: 5-alpha-androstan-3-alpha-17-beta-diol as the true inducer of kidney alcohol dehydrogenase and beta-glucuronidase

Androgen receptor positively regulates gonadotropin-releasing hormone receptor in pituitary gonadotropes

Within pituitary gonadotropes, the gonadotropin-releasing hormone receptor (GnRHR) receives hypothalamic input from GnRH neurons that is critical for reproduction. Previous studies have suggested that androgens may regulate GnRHR, although the mechanisms remain unknown. In this study, we demonstrated that androgens positively regulate Gnrhr mRNA in mice. We then investigated the effects of androgens and androgen receptor (AR) on Gnrhr promoter activity in immortalized mouse LβT2 cells, which represent mature gonadotropes. We found that AR positively regulates the Gnrhr proximal promoter, and that this effect requires a hormone response element (HRE) half site at -159/-153 relative to the transcription start site. We also identified nonconsensus, full-length HREs at -499/-484 and -159/-144, which are both positively regulated by androgens on a heterologous promoter. Furthermore, AR associates with the Gnrhr promoter in ChIP. Altogether, we report that GnRHR is positively regulated by androgens through recruitment of AR to the Gnrhr proximal promoter.

Androgen receptor (AR) pathophysiological roles in androgen-related diseases in skin, bone/muscle, metabolic syndrome and neuron/immune systems: lessons learned from mice lacking AR in specific cells

The androgen receptor (AR) is expressed ubiquitously and plays a variety of roles in a vast number of physiological and pathophysiological processes. Recent studies of AR knockout (ARKO) mouse models, particularly the cell type- or tissue-specific ARKO models, have uncovered many AR cell type- or tissue-specific pathophysiological roles in mice, which otherwise would not be delineated from conventional castration and androgen insensitivity syndrome studies. Thus, the AR in various specific cell types plays pivotal roles in production and maturation of immune cells, bone mineralization, and muscle growth. In metabolism, the ARs in brain, particularly in the hypothalamus, and the liver appear to participate in regulation of insulin sensitivity and glucose homeostasis. The AR also plays key roles in cutaneous wound healing and cardiovascular diseases, including atherosclerosis and abdominal aortic aneurysm. This article will discuss the results obtained from the total, cell type-, or tissue-specific ARKO models. The understanding of AR cell type- or tissue-specific physiological and pathophysiological roles using these in vivo mouse models will provide useful information in uncovering AR roles in humans and eventually help us to develop better therapies via targeting the AR or its downstream signaling molecules to combat androgen/AR-related diseases.

Histochemical studies on genetical control of hormonal enzyme inducibility in the mouse. V. Histochemical evidence for androgen inducibility of beta-glucuronidase in the epididymis

The enzyme beta-glucuronidase (beta G) is shown, by histochemical methods, to be androgen inducible in the mouse epididymis. This trait has previously been believed to exist only in the kidney. Its presence in the genital tract constitutes a valuable tool in study of the developmental genetics of the reproductive system. Data presented here and previously imply co-ordinated genetic control of heterogeneous lysosomal populations. The results reported also provide a system for study of X-chromosomal activation, and of the developmental androgen dependence of the epididymis.

Histochemical studies on genetical control of hormonal enzyme inducibility in the mouse. IV: Cellular localization of androgen sensitive nonspecific esterase in the epididymis

Nonspecific esterase of mouse epididymis has previously been studied histochemically, using alpha naphthyl-acetate and 5-bromoindoxyl acetate techniques, as well as certain inhibitors. Epithelial cell types of the epididymis have been characterized, and certain esterase isozymes in a particular cell type, is shown to be androgen dependent. When mice of different strains were castrated or treated with antiandrogens, the characteristic histochemical reaction product disappeared or was greatly reduced. Androgen treatment of castrated animals caused the reaction in the cells concerned to return to normal. This method can now be applied to the study of epididymides of genetically sex-reversed chromosomal female, to analyze genetic control of X-chromosomal activation.

The permissive role of glucocorticoids in the development of ethanol dependence and tolerance

In mice chronically treated with ethanol (in a liquid diet containing 6% ethanol ad libitum for 2 weeks), brain tryptophan hydroxylase (TPH) activity was increased (by 30-45% in whole brain), while brain tyrosine hydroxylase activity remained unchanged. Such chronic ethanol treatment also induced susceptibility to audiogenic seizures during withdrawal (60% incidence). When ethanol treatment was given to adrenalectomized (Adx) mice, the increase of brain TPH activity and the development of withdrawal audiogenic seizures were both prevented. In Adx mice receiving daily injections of corticosterone (0.5 mg/mouse), the ethanol-induced increase of brain TPH activity and the occurrence of withdrawal audiogenic seizures were both restored. Similarly, the ethanol-induced increase of liver alcohol dehydrogenase activity (by 60%) was prevented in Adx mice and restored by corticosterone replacement. It was noted that in all three cases replacement with such large doses of the corticoid did not enhance the ethanol effects, but merely restored the effects to the levels observed in intact mice. Apparently, glucocorticoids are required in a permissive role in order for the ethanol effects to occur.

Interconversion between 17 beta-hydroxy-5alpha-androstan-3-one (5alpha-dihydrotestosterone) and 5alpha-androstane-3alpha, 17 beta-diol in rat kidney: heterogeneity of 3alpha-hydroxysteroid oxidoreductases

3alpha-Hydroxysteroid oxidoreductases catalyzing the interconversion between 17 beta-hydroxy-5alpha-androstan-3-one (5alpha-dihydrotestosterone) and 5alpha-androstane-3alpha, 17 beta-diol (3alpha-androstanediol) have been studied in rat kidney. Three enzymes can be distinguished: a soluble NADPH-dependent oxidoreductase, a microsomal NADPH-dependent enzyme and a microsomal NADH-linked enzyme. Traces of the microsomal enzymes are consistently observed in the 108 000 X g supernatant. Studies on crude preparations reveal that these enzymes differ not only in subcellular localization and co-factor requirement, but also in optimum pH, kinetic characteristics, sensitivity to potential steroidal inhibitors and sensitivity to detergents, ionic strength and temperature. Moreover, salient sex differences exist in the activity of all three kidney enzymes. The soluble NADPH-dependent enzyme is more active in female rats whereas both microsomal enzymes are considerably more active in male animals. The microsomal NADH-dependent oxidoreductase displays favorable characteristics to catalyze the 3alpha-dehydrogenation of 3alpha-androstanediol. Evidence is presented that it is mainly this enzyme that enables the kidney to use 3alpha-androstanediol as an efficient precursor for the local formation of 5alpha-dihydrotestosterone.

Drug induction and sex differences of renal glutathione S-transferases in the rat

Treatment of male rats with 3,4-benzopyrene, 3-methylcholanthrene and phenobarbital resulted in the induction of glutathione S-aryl- and S-aralkyl-transferase activities in kidney cytosol. Benzopyrene produced 77 and 44% increases in aryl and aralkyl activities respectively. Methylcholanthrene caused 73 and 86% increases in the retrospective activities, whereas phenobarbital treatment increased only aralkyl activity (51%). There was no effect on epoxide or alkyl glutathione S-transferase activities with these treatments. Differences were found between the specific activities of the four glutathione S-transferases in females and males, with the following female/male ratios: aryl 0.74; aralkyl 2.37; epoxide 1.52; alkyl 1.33. No changes in Km values were observed relative to drug induction or sex differences. Comparisons are made between the findings of this report and corresponding experiements with liver.

Genetic and hormonal control of male sexual differentiation

Phenotypic sexual differentiation during embryogenesis is a complex process involving the action of at least 18 genes. These genes regulate gonadal differentiation, gonadal hormone formation, and in the male the cellular action of three necessary hormones, namely mullerian regression factor, testosterone, and dihydrotestosterone. Analysis of two of the mutations affecting sexual development is consistent with the thesis that the two androgens testosterone and dihydrotestosterone have separate and specific roles in virilization of the male urogenital tract, testosterone stimulating wolffian duct development and dihydrotestosterone mediating development of the urogenital sinus and external genitalia. In the disorder familial incomplete male pseudohermphroditism, type 2, deficient dihydrotestosterone formation is associated with a selective failure of virilization of the urogenital sinus and external genitalia, whereas the wolffian duct derivatives develop normally. On the other hand, in the testicular feminization syndrome there is a complete failure in the development of the male phenotype, indicating that the primary defect involves an abnormality in some biochemical step that is common to the action of both androgens. Evidence from studies in the submandibular gland of the mouse with testicular feminization suggest that the fundamental defect lies in the translocation and/or nuclear binding of the cytoplasmic androgen receptor. It remains to be proven whether these events in the postnatal, sexually dimorphic submandibular gland of the testicular feminization mouse reflect prenatal events occurring in the urogenital tissues during embryogenesis.

Mammalian liver alcohol dehydrogenases

Literature on the properties of liver alcohol dehydrogenase (ADH) from man, horse and rat is reviewed and discussed under two major headings: 1) physical and chemical properties of ADH and 2) structure-function relationship in isoenzymes. Under the first heading are discussed: molecular weight, subunit composition catalytic sites per molecule, sulfhydryl groups, end groups, amino acid composition, role of Zn++ in the structure and function, coenzyme specificity and binding, conformational changes, substrate specificity, catalytic mechanism and recent results from x-ray crystallography of horse liver ADH. The physicochemical properties of ADH from man, horse and rat are for the most part similar. All three enzymes have identical molecular weights, similar amino acid compositions, consist of two subunits, and are all metalloenzymes containing Zn++: horse and human ADH contain one coenzyme binding site per subunit; no results are available for the rat ADH. ADH catalyses interconversion of a large variety of saturated and unsaturated aliphatic and aromatic alcohols and the corresponding aldehydes and ketones utilizing NAD(H). The physiological role of ADH is uncertain. ADH readily combines with reduced coenzymes to form binary complexes with low dissociation constants (10-7 to 10-8M); in the ternary complexes with coenzymes and substrate-competitive inhibitors, these constants are even lower. In the presence of suitable inhibitors, the enzymes can be titrated by coenzymes employing fluorometric and spectrophotometric procedures. The rate of the overall reaction catalyzed by ADH is determined by the dissociation rates of coenzymes, the slowest steps in the reaction sequence. Under the second heading are discussed: liver ADH isoenzymes of horse, man, rat, rhesus monkey and other species, and the significance of steroid activity which accounts for the distinct substrate specificity of some isoenzymes. ADH from horse liver is a heterogeneous enzyme consisting of subunits of distinct substrate specificity and primary structure. The difference in the amino acid sequence between subunit E (active with classical ADH substrates, but not with steroids) and subunit S (active also with steroids) amounts to six amino acids out of 374. Human ADH is also heterogeneous, and at least five genes code for polypeptides which, by dimerization, form different isoenzymes. Experimental evidence suggests that rat ADH is a single unique protein which, like horse liver ADH, SS, is active with steroids. The physiological significance of steroid activity of ADHs is unknown. (Four tables with comparative data and one figure are presented).

Metabolism of testosterone- 14 C by cultured human cells

The metabolism of (14)C-labeled testosterone by cultured human fibroblasts and amniotic fluid cells was investigated. Radiolabeled testosterone was incubated with the cultured cells for 48 hr, and the labeled metabolites present in the medium were subsequently identified. The major metabolic products of testosterone formed by cultured fibroblasts were Delta(4)-androstenedione, dihydrotestosterone, androsterone, and androstanediol. The amount of testosterone metabolized through each of two pathways was calculated and used to form a ratio designated the 17beta-hydroxyl/17-ketonic ratio. Fibroblasts from normal male and female children and adult females had high 17beta-hydroxyl/17-ketonic ratios indicating testosterone metabolism occurred primarily through the 17beta-hydroxyl pathway. There was change in the pattern of testosterone metabolism with age in males, i.e., adult males had much lower 17beta-hydroxyl/17-ketonic ratios than did male children. The testosterone metabolism of fibroblast cultures derived from three children with testicular feminization and their mothers was compared to normal age and sexmatched controls. Fibroblasts of children with testicular feminization metabolized testosterone predominantly through the 17-ketonic pathway and manifested a pattern of testosterone metabolism distinctly different from their sex and age matched controls. The mothers of children with testicular feminization could be distinguished from normal females by their much lower 17beta-hydroxyl/17-ketonic ratios. The much lower amounts of dihydrotestosterone and androstanediol produced by fibroblasts from patients with testicular feminization as compared with normals suggests there is a decrease in testosterone 5alpha-reductase activity in these patients. Cultured amniotic fluid cells metabolized testosterone to the same four major metabolites found in fibroblast cultures, but their activity was much lower than that of fibroblasts. Most of the amniotic fluid cell cultures metabolized testosterone largely through the 17beta-hydroxyl pathway as did fibroblasts from normal children.