Deletion of steroid 5 alpha-reductase 2 gene in male pseudohermaphroditism

A clinician looks at androgen resistance

Androgen resistance in genetic males occurs when gonadotropins and testosterone are normal, but the physiological androgen response in androgen target organs is absent or decreased. In androgen-dependent target tissues two main defects may be found: 1) defective testosterone metabolism (5 alpha-reductase type 2 deficiency) and 2) anomalies in androgen receptors (androgen insensitivity syndrome (AIS)). The clinical manifestations of these defects vary from subjects with female external genitalia to subjects with mild forms of impaired masculinization. In particular, in the complete form of AIS (CAIS) the phenotype is feminine, and in the partial form (PAIS) the external genitalia are ambiguous with an extremely variable phenotype. The diagnosis requires clinical, hormonal, genetic, and molecular investigation for appropriate gender assignation and treatment. In AIS, cloning of androgen receptor cDNA using the polymerase chain reaction, denaturing gradient gel electrophoresis, and nucleotide sequencing have enabled a variety of molecular defects in the androgen receptor to be identified. The complexity of phenotypic presentation of AIS probably reflects the heterogeneity of androgen receptor gene mutations, but to date a relationship between genotype/phenotype has been difficult to establish, with the same point mutation reported to be associated with different phenotypic expressions. Other factors must therefore also contribute to the clinical presentation of AIS, although none have yet been identified. Establishing the functional consequences of androgen receptor mutations in vitro systems and correlating them with clinical presentation may ultimately provide an explanation for the variable clinical presentation of AIS and perhaps enable prediction of the response to androgen therapy in infants with PAIS.

Characterization of 17beta-hydroxysteroid dehydrogenase isoenzyme expression in benign and malignant human prostate

In the present study, expressions of 17beta-hydroxysteroid dehydrogenase (17HSD) types 1, 2, and 3, 5alpha-reductase type 2 and human androgen receptor mRNAs were determined in 12 benign prostatic hyperplasia and 17 prostatic carcinoma specimens. 17HSD type 2 was found to be the principle isoenzyme expressed in the prostate. Significantly higher expressions of 17HSD type 2 and 5alpha-reductase type 2 were detected in benign prostatic hyperplasia compared with the carcinoma specimens. Expression of the androgen receptor in the 2 groups was not significantly different. 17HSD type 3 mRNA was not detected in any of the specimens investigated. Only low constructive expression of the 2.3 kb mRNA of 17HSD type 1 was seen. Immunohistochemical analysis indicated that this did not lead to significant enzyme expression, only faint staining for the enzyme protein being detected, mainly in uroepithelial cells. No significant correlation was found between any of the mRNAs analysed, but the data on 5alpha-reductase type 2 mRNA support the presence of an increased proportion of 5alpha-dihydrotesterone in the hyperplastic prostate. In cultured PC-3 prostatic cancer cells and in the transiently transfected human embryonic kidney 293 cells, 17HSD type 2 was found exclusively to convert 5alpha-dihydrotestosterone and testosterone into the less potent 17-keto compounds 5alpha-androstanedione and 4-androstenedione, respectively. We suggest that the 17HSD type 2 isoenzyme plays a part in the metabolic pathway, resulting in the inactivation of testosterone and 5alpha-dihydrotestosterone locally in the prostate. The enzyme expressed in the prostate could, therefore, protect cells from excessive androgen action.

Characterization of rat 5alpha-reductases type 1 and type 2 expressed in Saccharomyces cerevisiae

Two isoforms of the rat 5alpha-reductase (5alpha-R), the enzyme that converts testosterone into dihydrotestosterone (DHT), and other delta4-3-keto steroids (e.g. progesterone and corticoids) into their 5alpha-reduced metabolites, have been cloned. In this study, a convenient and efficient system was developed to overexpress the two isoenzymes in Saccharomyces cerevisiae by using the ubiquitin-fusion expression system. Two yeast expression vectors have been prepared, YEpR1 and YEpR2, which code for 5alpha-R type 1 and 5alpha-R type 2 respectively; they contain the copper-responsive yeast metallothionein promoter (CUP1) upstream of the ubiquitin coding sequence, and the full-length rat 5alpha-R type 1 or 5alpha-R type 2 cDNAs in frame to the 3' end of the ubiquitin cDNA. The activity of the two isoenzymes produced in yeast was determined in cell lysates at the enzyme pH optima (type 1, pH 7.5; type 2, pH 5.5) and a possible differential intracellular distribution was also evaluated. The kinetic parameters were: type 1, Km 4.6 microM, Vmax.100.6 micrograms/h per mg of protein; type 2, Km 68.6 nM, Vmax. 0.84 micrograms/h per mg of protein. Yeast cell lysates were fractionated by differential centrifugation and the 5alpha-R type 1 activity was maximal in fractions containing nuclei (1000 g and 2500 g), whereas the maximal activity of 5alpha-R type 2 was present in subcellular fractions sedimenting at higher speeds (20000g). The data indicate that yeasts overexpress the two 5alpha-R isoenzymes, maintaining their native biochemical properties, and that the two isoforms are probably differentially localized within the yeast cell.

Male pseudohermaphroditism due to steroid 5alpha-reductase 2 deficiency. Diagnosis, psychological evaluation, and management

Sixteen subjects (from 10 Brazilian families) with male pseudohermaphroditism due to steroid 5alpha-reductase 2 deficiency have been evaluated in 1 clinic. The diagnoses were made on the basis of normal plasma testosterone values, normal or low plasma dihydrotestosterone levels and high testosterone/dihydrotestosterone ratios in the basal state in postpubertal subjects or after treatment with either human chorionic gonadotropin or testosterone in prepubertal subjects. The analysis of the ratios of etiocholanolone to androsterone in urine confirmed the diagnosis in all subjects who were tested, and the molecular basis of the underlying mutations was established in 9 of the families. Fourteen of the individuals were evaluated by the same psychologist. All subjects but 1 were given a female sex assignment at birth. Three of the subjects (1 the sibling of an individual who has undergone female to male social behavior) maintain a female social sex; they have been gonadectomized and treated with exogenous estrogens. Ten of 13 subjects of postpubertal age underwent a change of social sex from female to male, had surgical correction of the hypospadias, and were treated with high-dose testosterone esters by parenteral injection and subsequently with dihydrotestosterone cream. These regimens brought serum dihydrotestosterone levels to the normal male range (or above) but resulted only in limited growth of the prostate and penis and, in some, increase in body and facial hair and enhancement of libido and sexual performance. Treatment of the prepubertal boys with testosterone and/or dihydrotestosterone resulted in a doubling of penis size.

Heterogeneity of rat type I 5 alpha-reductase cDNA: cloning, expression and regulation by pituitary implants and dihydrotestosterone

Primer extension analysis reveals the presence of different forms of mRNA species for rat type I 5 alpha-reductase. Using a 5 alpha-reductase cDNA probe to screen the rat liver lambda gt11 cDNA library, we isolated cDNA clones that have 4 additional amino acids in the NH2-terminal region as compared with the previously reported sequence for rat type I 5 alpha-reductase. These four additional amino acids elongate the rat type I 5 alpha-reductase amino acid sequence to 259 amino acids, the same number as in human type I 5 alpha-reductase, with which it shares 60% identity. Expression of the long and short rat type I 5 alpha-reductase by transfection in human adrenal adenocarcinoma cells, SW-13 cells, indicated that the long cDNA encoded a protein with a higher affinity for the substrate than the short cDNA. To determine the effect of pituitary hormones and dihydrotestosterone (DHT), the mRNA levels in the livers of rats treated with pituitary implants, hypophysectomized, castrated, and castrated coupled with DHT treatment were quantified by dot-blot hybridization assay using rat type I 5 alpha-reductase cDNA as probes. The results demonstrated that rat type I 5 alpha-reductase mRNA is stimulated by pituitary hormones and castration but is decreased by DHT and hypophysectomy.

Immunocytochemical localization of 5 alpha-reductase type 1 in the prostate of normal and castrated rats

We immunohistochemically studied the localization of 5 alpha-reductase type 1 in combination with androgen receptor (AR) expression in individual lobes of the prostates of intact and castrated rats. In the normal rat prostate, 5 alpha-reductase was localized in the cytoplasm of most epithelial cells in the ventral, dorsal, and lateral type 1 (L1) lobes. Epithelial cells of lateral type 2 (L2) lobes were negative for 5 alpha-reductase. AR was present in the nuclei of all epithelial and stromal cells throughout the prostate. The number of 5 alpha-reductase-immunoreactive cells rapidly decreased in the ventral and L1 lobes after castration, whereas many positive cells remained in the dorsal lobe even at 4 weeks after castration. AR immunostaining was lost in the ventral, dorsal, and L1 lobes at 1 week after castration, but remained in the L2 lobe of 4-week-castrated rats. Electron microscopic immunocytochemistry showed that 5 alpha-reductase was exclusively localized in the rough endoplasmic reticulum membranes and that there were no distinct structural differences between the positively and negatively stained epithelial cells. These findings suggested that the expression of 5 alpha-reductase type 1 in the epithelial cell is heterogeneous within and among the individual lobes of the rat prostate, and does not correspond to AR expression.

Localisation of pseudohypoaldosteronism genes to chromosome 16p12.2-13.11 and 12p13.1-pter by homozygosity mapping

Pseudohypoaldosteronism type 1 (PHA1, OMIM 264350) is a rare Mendelian disorder characterised by end-organ unresponsiveness to mineralocorticoids. Most steroid hormone insensitivity syndromes arise from mutations in the corresponding receptor, but available genetic evidence is against involvement of the mineralocorticoid receptor gene, MLR, in PHA1. A complete genome scan for PHA1 genes was undertaken using homozygosity mapping in 11 consanguineous families. Conclusive evidence of linkage with heterogeneity was obtained with a maximum two-locus admixture lod score of 9.9. The disease locus mapped to chromosome 16p12.2-13.11 in six families and to 12p13.1-pter in the other five families. The two chromosomal regions harbour genes for subunits of the amiloride-sensitive epithelial sodium channel: SCNN1B and SCNN1G on 16p and SCNN1A on 12p. Liddle's syndrome of hypertension and pseudoaldosteronism has been shown to arise from mutations in SCNN1B and SCNN1G. These results strongly suggest that PHA1 and Liddle's syndrome are allelic variants caused by mutations in genes encoding subunits of this sodium channel. These genes are of broad biological interest both in relation to sodium and water homeostasis in mammals and by virtue of their homology to the mec genes of Caenorhabditis elegans involved in mechanosensitivity and neuronal degeneration.

Kinetic analysis of rat steroid 5alpha-reductase activity in prostate and epididymis homogenates at neutral pH: evidence for type I activity in epididymis

Immunocytochemical studies and mRNA measurements have shown that the rat epididymis--like the rat prostate--expresses both rat steroid 5alpha-reductase isozymes, i.e. type I and II. So far, enzyme activity measurements in rat epididymis homogenates, however, do not support the presence of type I 5alpha-reductase activity. Incubating homogenates of both tissues with a wide range of substrate concentrations, we were able to detect activity of both isozymes in rat prostate and epididymis tissues at neutral pH. In rat prostate the amount of type I activity, as measured by the Vmax at pH 7.0, exceeds that of type II 5alpha-reductase 50-fold. The efficiency ratio, Vmax/Km, of the type I isozyme accounts for 25% of the total in vivo potential activity. A possible anabolic role for the type I isozyme in rat prostate was thus surmised. In rat epididymis the Vmax of type I and type II 5alpha-reductase at pH 7.0 were similar. Comparison of the efficiency ratio Vmax/Km of either isozyme in the rat epididymis, however, suggested that the type II isozyme would play the major role in the 5alpha-reduction of testosterone at physiological concentrations and at neutral pH. The specific localization of the isozymes should be considered to allow for correct quantification of their in vivo contribution to dihydrotestosterone formation.

Vinyl fluoride as a mimic of the "intermediate' enol form in the 5 alpha-reductase transformation: synthesis and in vitro activity of (N-1',1'-dimethylethyl)-3-haloandrost-3,5-diene-17 beta-carboxamides

(N-1',1'-Dimethylethyl)-3-haloandrost-3,5-diene-17 beta-carboxamides (9-11) and the methyl ester 8 were prepared from 3-chloro/bromoandrost-3,5-diene-17 beta-carboxylic chloride/bromide (6/7), which were obtained from pregnenolone. In comparison with finasteride and 4-MA, compounds 8-11 showed very weak inhibitory activity ( < or = 10% inhibition) on human type I 5 alpha-reductase (transfected 293 cells) at 100 and 1000 nM concentrations. Against the type II enzyme, chloro compounds 8 and 9, and bromo 10 had no effect at 100 nM concentration, however, they were weak inhibitors of the type II (6.0% < inhibition < 30%) at a higher concentration. The best activity (IC50 = 480 nM) was observed with the 3-vinyl fluoride analogue 11.

Testosterone metabolism in primary cultures of human prostate epithelial cells and fibroblasts

We compare testosterone (T) metabolism in primary cultures of epithelial cells and fibroblasts separated from benign prostate hypertrophy (BPH) and prostate cancer tissues. In all cultures, androstenedione (delta 4) formed by oxidation of T by 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) represented 80% of the metabolites recovered. The amounts of 5 alpha-dihydrotestosterone (DHT), formed by reduction of T by 5 alpha-reductase (5 alpha-R), were small: 5 and 2% (BPH) and 8 and 15% (adenocarcinoma) for epithelial cells and fibroblasts, respectively. Northern blot analysis of total RNA from epithelial cells (BPH or adenocarcinoma) attributed the reductive activity to the 5 alpha-reductase type 1 isozyme and oxidative activity to the 17 beta-HSD type 2. In cancer fibroblasts, only little 17 beta-HSD type 2 mRNA was detected. The 5 alpha-reductase inhibitors, 4-MA (17 beta-(N,N-diethyl)carbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one) and finasteride, inhibited DHT formation with a preferential action of 4-MA on epithelial cells (BPH or adenocarcinoma) and of finasteride on fibroblasts from adenocarcinoma. Neither inhibitor acted on delta 4 formation. On the other hand, the lipido-sterol extract of Serenoa repens (LSESr, Permixon) inhibited the formation of all the T metabolites studied [IC50 S = 40 and 200 micrograms/ml (BPH) and 90 and 70 micrograms/ml (adenocarcinoma) in epithelial cells and fibroblasts, respectively]. These results have important therapeutic implications when selecting appropriate treatment options for BPH.

Finasteride inhibits 5 alpha-reductase activity in human dermal fibroblasts: prediction of its therapeutic application in androgen-related skin diseases

BACKGROUND

The potential role of finasteride in treating androgen related skin disorders was investigated.

METHODS

Pooled human dermal fibroblasts were used to assess the effect of finasteride on the 5 alpha-reductase activity in skin tissue. Vmax and Km were estimated in the presence of 0, 10, and 200 nM finasteride.

RESULTS

Vmax values remain constant near 1.20 pmol/mg protein/h in the presence of increasing concentrations of finasteride; however, apparent Km increases from 0.27 nM at 0 nM finasteride to 0.31 nM and 0.44 nM at 10 nM and 200 nM finasteride, respectively. This suggests that finasteride competes with testosterone and has a high affinity for same binding site of the 5 alpha-reductase enzyme. Apparent Ki was estimated at 282 nM, indicating that a high concentration of finasteride is required to significantly suppress the enzyme activity.

CONCLUSIONS

This study confirms that finasteride inhibits the conversion of testosterone to dihydrotestosterone in human reticular dermal fibroblasts. Finasteride may have therapeutic potential in treating skin disorders influenced by the action of dihydrotestosterone.

Immunohistochemical evidence for differential distribution of 5 alpha-reductase isoenzymes in human skin

Antibodies raised against fragments of synthetic peptides of human 5 alpha-reductase isoenzymes 1 (h5 alpha r1) and 2 (h5 alpha r2) were applied to paraffin sections of human skin (scalp, eyelid, lip, breast, scrotum). Immunoreactive sites were differentially distributed, in that h5 alpha r1 immunoreactivity was present in the nuclei of cells in the stratum germinativum (basal and lower portion of the spinous layer) of the epidermis, subepithelial fibroblasts, adipocytes, smooth muscle cells of the scrotal tunica dartos, basal cells of sebaceous glands, excretory duct cells of sweat glands, cells of the dermal papilla and fibrous and outer epithelial sheath of hair roots, as well as endothelial cells of small vessels and Schwann cells of cutaneous myelinated nerves. In contrast, immunoreactivity for h5 alpha r2 was found in the cytoplasm of the cells of the spinous layer (and far less intensely in the basal layer) of the epidermis, subepidermal fibrocytes, and especially in subcutaneous adipocytes. Immunoreactivity was strongest in the non-keratinized portion of the inner epithelial sheath and the cuticle of hair follicles, whereas other portions of the hair root were negative. Sweat glands were stained, whereas sebaceous glands showed only weak diffuse immunoreactivity. In mucocutaneous zones, salivary glands and conjunctival epithelium showed immunoreactive cells. Vascular endothelium displayed immunoreactivity only in the genital region. We present experimental evidence for a differential distribution of 5 alpha-reductase isoenzymes in human skin. This might reflect a diversity in the response of different areas of the skin to androgenic challenge.

Human prostatic steroid 5 alpha-reductase isoforms--a comparative study of selective inhibitors

The present study describes the independent expression of the type 1 and 2 isoforms of human 5 alpha-reductase in the baculovirus-directed insect cell expression system and the selectivity of their inhibition. The catalytic properties and kinetic parameters of the recombinant isozymes were consistent with published data. The type 1 isoform displayed a neutral (range 6-8) pH optimum and the type 2 isoform an acidic (5-6) pH optimum. The type 2 isoform had higher affinity for testosterone than did the type 1 isoform (Km = 0.5 and 2.9 microM, respectively). Finasteride and turosteride were selective inhibitors of the type 2 isoform (Ki (type 2) = 7.3 and 21.7 nM compared to Ki (type 1) = 108 and 330 nM, respectively). 4-MA and the lipido-sterol extract of Serenoa repens (LSESr) markedly inhibited both isozymes (Ki (type 1) = 8.4 nM and 7.2 micrograms/ml, respectively; Ki (type 2) = 7.4 nM and 4.9 micrograms/ml, respectively). The three azasteroids were competitive inhibitors vs substrate, whereas LSESr displayed non-competitive inhibition of the type 1 isozyme and uncompetitive inhibition of the type 2 isozyme. These observations suggest that the lipid component of LSESr might be responsible for its inhibitory effect by modulating the membrane environment of 5 alpha-reductase. Partially purified recombinant 5 alpha-reductase type 1 activity was preserved by the presence of lipids indicating that lipids can exert either stimulatory or inhibitory effects on human 5 alpha-reductase.

Clinical and endocrine effects of finasteride, a 5 alpha-reductase inhibitor, in women with idiopathic hirsutism

OBJECTIVE

To evaluate the effects of long-term administration of finasteride on hirsutism score, basal gonadotropin, and androgen secretion in women with idiopathic hirsutism.

DESIGN

Randomized single-blinded study.

PATIENTS

Eighteen patients with moderate-severe hirsutism were recruited for the study.

INTERVENTIONS

Nine hirsute patients received 7.5 mg/d oral finasteride for a period of 9 months whereas the other nine were treated with placebo. Hirsutism score, serum basal gonadotropin, androgens, estrogen, and sex hormone-binding globulin (SHBG) levels were evaluated in all patients before treatment and every 3 months during treatment.

RESULTS

After 6 and 9 months of treatment, the hirsutism score improved significantly in the patients receiving finasteride, whereas no significant modifications were observed in patients treated with placebo. The side effects observed were headache and depression of modest entity during the 1st month of treatments, whereas libido did not change. Serum levels of LH, FSH, androstenedione, unbound T, DHEAS, E2, 17 alpha-hydroxyprogesterone, and SHBG did not change during therapy. Hirsute patients treated with finasteride exhibited a marked decrease of dihydrotestosterone and a significant increase of T serum levels from the 3rd and 6th months of treatment, respectively.

CONCLUSION

Finasteride decreased the hirsutism score of patients affected by idiopathic hirsutism with few side effects during treatment. No modification of libido was observed.

Activity of the type 1 5 alpha-reductase exhibits regional differences in isolated sebaceous glands and whole skin

The presence of 5 alpha-reductase (5 alpha-R) in skin may indicate that the androgen regulation of sebaceous glands and sebum production requires the local conversion of testosterone to dihydrotestosterone. The goals of this study were to identify which isozyme of 5 alpha-R (type 1 or type 2) is expressed in sebaceous glands from facial areas, scalp, and non-acne-prone areas; to determine if 5 alpha-R activity is concentrated in sebaceous glands; to assess whether there are regional differences in this enzyme's activity; and to test the effects of azasteroid inhibitors and 13-cis retinoic acid on 5 alpha-R in these tissues. Sebaceous glands were microdissected from facial skin, scalp, and non-acne-prone skin (arm, breast, abdomen, leg), and the activity of 5 alpha-R was determined. A total of 49 samples from 23 male and 21 female subjects without acne (age range, 16 to 81 years, 56 +/- 20 years [mean +/- SD]) was analyzed. The biochemical properties of the enzyme in each of the samples tested are consistent with those of the type 1 5 alpha-R. Minimal to no type 2 5 alpha-R was detected. The level of 5 alpha-R activity was significantly higher in the sebaceous glands compared to whole skin in facial skin (p = 0.047), scalp (p = 0.039), and non-acne-prone skin (p = 0.04). Enzyme activity in sebaceous glands from facial skin and scalp was significantly higher than in a comparable amount of sebaceous gland material obtained from non-acne-prone areas (32 +/- 6 [mean +/- SEM]), 35 +/- 7 (mean +/- SEM) versus 6.0 +/- 3.0 (mean +/- SEM) pmol/min/mg protein, p = 0.014 and 0.007, respectively). Finasteride and 13-cis retinoic acid were poor inhibitors of the enzyme with 50% inhibitory concentration values greater than 500 nM. These data demonstrate that in the skin from older patients without acne the type 1 isozyme of 5 alpha-R predominates, its activity is concentrated in sebaceous glands and is significantly higher in sebaceous glands from the face and scalp compared to non-acne-prone areas, and the action of 13-cis retinoic acid in the control of acne is not at the level of 5 alpha-R. Furthermore, we suggest that specific inhibition of the type 1 5 alpha-R may offer a viable approach to the management of sebum production and, hence, acne.

A new deletion of the 5 alpha-reductase type 2 gene in a Turkish family with 5 alpha-reductase deficiency

The molecular basis for male pseudohermaphroditism produced by the 5 alpha-reductase deficiency is becoming increasingly understood.

OBJECTIVE

We have performed biochemical and molecular analyses of the 5 alpha-reductase type 2 gene in a Turkish family with a 5 alpha-reductase deficiency.

PATIENT

A 46,XY prepubertal Turkish patient with female phenotype showing clitoral hypertrophy, high plasma testosterone and dihydrotestosterone, and normally differentiated and developed testosterone-dependent internal genitalia.

MEASUREMENTS

5 alpha-Reductase activity, measured by the conversion of 3H-T into 5 alpha-reduced compounds, was determined from cultured genital skin fibroblasts by both intact monolayer assay and cell-free extracts at various pH values. The five exons of the 5 alpha-reductase type 2 gene were sequenced after enzymatic amplification (PCR) of the patient's genomic DNA. Labelled PCR of the consanguineous parents' DNA was submitted to electrophoresis on a sequencing gel.

RESULTS

A marked decrease in the transformation of T into 5 alpha-reduced compounds by intact cells and a diminished 5 alpha-reductase activity at acidic pH by sonicated cell extracts strongly suggested a 5 alpha-reductase type 2 deficiency. Molecular analysis of the 5 alpha-reductase type-2 gene showed a trinucleotide deletion straddling codons 156 and 157, responsible for a methionine residue deletion at position 157 of the protein. The parents' DNA contained both normal and deleted alleles.

CONCLUSIONS

This is the third deletion described in the 5 alpha-reductase type 2 gene. The deleted methionine 157 is conserved in both types 1 and 2 of human and rat 5 alpha-reductase, which suggests its crucial role in the functioning of the enzyme. This gene rearrangement was thus clearly responsible for the reduced 5 alpha-reductase activity and abnormal genital development in this patient.

Rat steroid 5 alpha-reductase kinetic characteristics: extreme pH-dependency of the type II isozyme in prostate and epididymis homogenates

Reevaluating the assay for rat steroid 5 alpha-reductase isozymes in prostate and epididymis homogenates we encountered an extreme pH-dependency of the type II isozyme. The time-course of the metabolism of testosterone (T) to 17 beta-hydroxy-5 alpha-androstan-3-one (DHT) at acidic pH shows an initial burst when the homogenate is not brought to pH before the start of the incubation. Therefore, the rat type II 5 alpha-reductase isozyme does not follow Michaelian law under these conditions making a single time point measurement invalid. Assessing the pH-optimum of 5 alpha-reduction in both rat prostate and epididymis homogenates we found a strong substrate dependency: at high substrate concentrations a pH-optimum for the type II isozyme of pH 5.0 was found, whereas at lower concentrations pH 5.5 is optimal. Establishing Vmax (maximum velocities) and Km (affinity constants) for the 5 alpha-reduction of T at pH 4.5-8.0, the efficiency optimum Vmax/Km appeared to be pH 5.5 in both prostate and epididymis homogenates. Specifically at acidic pH these kinetic characteristics of the type II isozyme vary many-fold. Discrepancies in literature concerning 5 alpha-reductase characteristics can, at least in part, be attributed to the choice of optimal pH, or to pH shifts during the assay.

Disorders of sexual development

Over the past 6 years, the structures of four key genes involved in sexual differentiation have been identified (see Figure 2). Mutations within these genes have been demonstrated to cause a significant percentage of the disorders of sexual differentiation described in this chapter. It should be noted, however, that there are significant numbers of patients with these disorders in whom no mutation in any of these genes has yet been characterized. It is probable that further genes involved in sexual differentiation will be identified and shown to be the cause of a number of these diseases.

The enzyme and inhibitors of 4-ene-3-oxosteroid 5 alpha-oxidoreductase

Since evidence of 5 alpha-reductase activity in rabbit liver homogenate was discovered in 1954, the presence of this enzyme has been demonstrated in many other organs and tissues of mammalian species. 5 alpha-Reductase selectively transforms a 4-ene-3-oxosteroid (e.g., testosterone) irreversibly to the corresponding 5 alpha-3-oxosteroid (e.g., 5 alpha-dihydrotestosterone) in the presence of NADPH as an essential coenzyme at an optimal pH. However, excessive production of 5 alpha-dihydrotestosterone is the major cause of many androgen-related disorders, such as prostate cancer, benign prostatic hyperplasia, acne, female hirsutism, and male pattern baldness; therefore, inhibition of androgenic action by 5 alpha-reductase inhibitors is a logical treatment. During the past two decades, research has focused on understanding the biological functions and effects of 5 alpha-reductase and its 5 alpha-reduced metabolites: purification of the enzyme, substrates, and metabolites; characterization of their physical, chemical, and biochemical properties; analysis of the amino acid sequence of the enzyme; synthesis of various classes of molecules as potential inhibitors; and examination of the biological activity of the inhibitors in vitro and/or in vivo. This review summarizes the biochemical studies on this enzyme, suggests the mechanisms of action of the enzyme or inhibitors, and discusses the chemistry necessary for the preparation, structure-activity relationships, and in vitro and/or in vivo data obtained from the evaluation of nonsteroidal and steroidal compounds that have been tested as inhibitors of 5 alpha-reductase. In particular, IC50 and Ki values for relevant compounds will be compared according to molecular class. This review could function as a comprehensive working reference of what research has been accomplished so far and what problems remain to be solved in the future for those engaged in this interesting field.

Effects of 5 alpha-reductase inhibitors on intraprostatic androgens in the rat

FCE 27837 is a novel inhibitor of 5 alpha-reductase, the enzyme responsible for the conversion of testosterone (T) to 5 alpha-dihydrotestosterone (DHT). The compound caused inhibition of human and rat prostatic enzymes, with IC50 values of 51 and 60 nM, respectively. The in vivo effect of FCE 27837 on 5 alpha-reductase was evaluated in adult male rats, treated orally at 10 mg/kg/day for 10 days. The compound caused 33 and 42% reductions in ventral prostate and seminal vesicle weights, respectively. The prostatic content of DHT, measured 6 h after the 10th dose of FCE 27837, was reduced by 75%, whereas T content increased by 442%. Similar effects were observed with 10 mg/kg/day of finasteride, whereas epristeride, tested at the same oral dose, was found to be the least effective compound, decreasing prostate weight by 22% and DHT content by 46%. Castration caused > 90% reductions in prostatic weight and prostatic DHT.

Structural characterization and expression of the human dehydroepiandrosterone sulfotransferase gene

Dehydroepiandrosterone sulfotransferase catalyzes the transformation of dehydroepiandrosterone to dehydroepiandrosterone sulfate, the most abundant steroid in circulation in the human and primate. Dehydroepiandrosterone sulfate serves as precursor for the formation of active androgens and estrogens in peripheral target tissues. In addition, blockade at the dehydroepiandrosterone level could give raise to high level of DHEA and thus disorders due to mild excess of androgen. Recently, the cDNA encoding dehydroepiandrosterone sulfotransferase has been isolated from a human liver cDNA library. To study the regulation and expression, as well as the possible defect linked to DHEA sulfotransferase gene, we have isolated and characterized its structure by screening a lambda EMBL3 library of human leukocyte genomic DNA using human dehydroepiandrosterone sulfotransferase cDNA as a probe. Sequencing of the gene shows that it is included in approximately 17 kb and contains six exons separated by five introns. Northern blot analysis shows a strong signal in the adrenals and liver, whereas no signal was detected in the spleen, thymus, prostate, testis, ovary, small intestine, colon, peripheral blood leukocytes, heart, brain, placenta, lung, skeletal muscle, kidney, or pancreas. Using primer extension analysis, the transcription start site is located at nucleotide 98 upstream from the ATG initiating codon. Putative TATA and CAAT boxes are situated at positions 72 and 96 upstream from the transcription start site, respectively. Using DNA from a panel of human/rodent somatic cell hybrids, and amplification of the gene by the polymerase chain reaction, the human dehydroepiandrosterone sulfotransferase gene has been assigned to chromosome 19.

Cations inhibit specifically type I 5 alpha-reductase found in human skin

Steroid 5 alpha-reductase catalyzes the reduction of testosterone into the very potent androgen dihydrotestosterone. Previously, we showed that human type I 5 alpha-reductase is expressed mainly in the skin, whereas a type II 5 alpha-reductase is more specifically expressed in the prostate. To assess the possible differential effects of various cations on the two types of 5 alpha-reductase, we constructed expression vectors and transfected them into SW-13 cells, a human adrenal carcinoma cell line containing negligible endogenous 5 alpha-reductase activity. The expressed 5 alpha-reductases were analyzed for their sensitivity to Li, Ca, Cd, Cu, Mg, Mn, Ni, Zn, and Fe. The results showed that type I 5 alpha-reductase was strongly inhibited by Cd, Cu, and Zn and moderately inhibited by Ni and Fe, with 50% inhibitory concentration values of 0.9, 1.9, 2.0, 169.2, and 174.3 microM, respectively. In contrast, type II 5 alpha-reductase activity was inhibited only by Cu, with a 50% inhibitory concentration value of 19.2 microM. The data showed that cations could specifically control 5 alpha-reductase activity expression, which is more strongly inhibited in a target tissue, especially the skin.

5 alpha-Reductase type 1 is localized to the outer nuclear membrane

The subcellular distribution of the two isozymes of 5 alpha-reductase has been controversial. To resolve this issue which could provide clues about the respective functions of the two isozymes, two antisera were generated, one which was specific for the Type 1 5 alpha-reductase and one which recognized both isozymes. In COS cells transfected separately with the Type 1 or Type 2 cDNA, both isozymes were detected on Western blots at an M(r) of 26,000. Subfractionation of the COS cells resulted in the partitioning of both isozymes between the crude nuclear and cytosolic fractions, while cytoimmunofluorescence localized both reductases to the nuclear periphery. In rat liver homogenate, the 5 alpha-reductase was also detected at M(r) 26,000. The 5 alpha-reductase immunoreactivity was increased after castration of the animals with no further effect when castrated animals were treated with androgens. Although the rat liver expresses only the Type 1 5 alpha-reductase, the 5 alpha-reductase was distributed about equally between crude nuclear and cytosolic subfractions; this distribution could be shifted to the cytosolic fractions with harsher homogenization procedures. Further extensive subfractionation and extraction studies identified the rat liver Type 1 5 alpha-reductase as an integral membrane protein present in the outer nuclear membrane of the nuclear envelope and in rough endoplasmic reticulum. Thus, the subfractionation and cytoimmunofluorescence studies are consistent with the localization of the Type 1 5 alpha-reductase to the outer nuclear membrane of the nuclear envelope which is continuous with and indistinguishable from the endoplasmic reticulum. This study is the first to localize rat liver Type 1 5 alpha-reductase to the nuclear envelope to which the prostatic 5 alpha-reductase activity previously had been localized. We conclude that, contrary to previous tissue distribution studies, but consistent with investigations in transfected cells, both isozymes are similarly localized to the nuclear periphery.

Cloning, expression and functional characterization of type 1 and type 2 steroid 5 alpha-reductases from Cynomolgus monkey: comparisons with human and rat isoenzymes

The Cynomolgus monkey may provide an alternative pharmacological model in which to evaluate the efficacy of novel inhibitors of the two known human steroid 5 alpha-reductase (SR) isoenzymes. To evaluate the suitability of this species at the level of the molecular targets, a Cynomolgus monkey prostate cDNA library was prepared and screened using human SR type 1 and 2 cDNAs as hybridization probes. Two distinct cDNA sequences were isolated encoding the monkey type 1 and 2 SR isoenzymes. These sequences share 93 and 95% amino acid sequence identity with their human enzyme counterparts, respectively. Difference in monkey type 1 SR, however, was found within the contiguous four amino acids corresponding to the regions in the human and rat sequences that have been proposed previously to influence steroid and inhibitor affinities. Subsequently, both monkey cDNAs were individually expressed in a mammalian cell (CHO) line. Enzyme activities of both monkey SRs were localized to the membrane fractions of CHO cell extracts. Like the human and rat enzymes, the monkey type 1 and type 2 SRs were most active at neutral and low pH, respectively. The results of inhibition studies with over 30 known SR inhibitors, including epristeride, 4MA, and finasteride, indicate that the monkey SR isoenzymes are functionally more similar to the human than the rat homologues. The results from initial velocity and inhibition studies as functions of pH with the human and monkey type 2 SRs also compare favorably. These results, together, suggest that the monkey SR isoenzymes are structurally and functionally comparable on a molecular level to their respective human counterparts, supporting the relevance and use of the Cynomolgus monkey as a pharmacological model for in vivo evaluation of SR inhibitors.

FK143, a novel nonsteroidal inhibitor of steroid 5 alpha-reductase: (1) In vitro effects on human and animal prostatic enzymes

Steroid 5 alpha-reductase is an enzyme which converts testosterone into 5 alpha-dihydrotestosterone (DHT) and is implicated in the pathogenesis of benign prostatic hyperplasia (BPH) in men. We studied in vitro effects of FK143, a nonsteroidal new compound, on 5 alpha-reductase in human and animal prostates. Prostates were obtained from Wistar rats, Beagle dogs, and Cynomolgus monkeys as well as prostatic tissue from BPH patients obtained by the prostatectomy. Nuclear membrane fraction of prostates showed pH dependent 5 alpha-reductase activities, and inhibitory effects of drugs were assayed at pH 6.5. FK143 inhibited human prostatic 5 alpha-reductase in a dose-dependent manner with an IC50 of 1.9 nM and also inhibited animal 5 alpha-reductases with similar IC50 values. FK143 inhibited human and rat 5 alpha-reductases in a noncompetitive fashion while finasteride, a steroidal 5 alpha-reductase inhibitor, showed competitive inhibition. The affinities of FK143 for the human 5 alpha-reductase is constant at pH 5 and 6.5. No inhibitory effects were shown to other oxidoreductases. These results indicate that FK143 is a new type of potent and selective 5 alpha-reductase inhibitor.

Male pseudohermaphroditism due to primary 5 alpha-reductase deficiency: variation in gender identity reversal in seven Mexican patients from five different pedigrees

In the present study, we describe the clinical, endocrinological, psychosexual and biochemical features of 7 Mexican male pseudohermaphrodites with primary 5 alpha-reductase deficiency in whom heterogeneity in the pattern of gender identity change at puberty was observed. The patients belonged to 5 different pedigrees from diverse locations in Mexico. Six of them were admitted to the Hospital during or after puberty. The one prepubertal subject was the sibling of a previously studied patient. Basal serum gonadotropins were determined by double antibody radioimmunoassay. Basal and choriogonadotropin (CG)-stimulated concentrations of androstenedione (A), testosterone (T) and dihydrotestosterone (DHT) were determined by radioimmunoassay after extraction and separation by celite chromatography. Urinary aetiocholanolone, androsterone and C19 and C21 5 beta/5 alpha metabolite ratios were analyzed by capillary gas chromatography. Enzyme activity and androgen receptors were studied in fibroblasts cultured from genital skin. Psychological assessment was performed using the Bender-Gestalt Wechsler Adult Intelligence Scale, the Rorschach Ink Blot and the Thematic Apperception Tests. All 7 patients were unambiguously reared as females; three spontaneously changed their gender identity and role from female to male after puberty, another one changed during psychotherapy at the end of puberty. Two patients (one prepubertal and the other pubertal) have been under therapy during 1.5 years, but due to familial and social factors a female gender has prevailed. The remaining patient consulted at age 15 because of virilization; her female gender identity did not change after more than one year of treatment and due to the fact she was depressed and had suicidal tendencies, the penis and testes were removed.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and biochemical evaluation of (carbamoylalkenyl)phenyloxy carboxylic acid derivatives as non-steroidal 5 alpha-reductase inhibitors

Several (carbamoylalkenyl)- and (carbamoylalkenyl)phenyloxy carboxylic acids (Table 1) and some of their ethyl esters (Table 2) were synthesized and evaluated in vitro as inhibitors of steroid 5 alpha-reductase. Inhibitors of this enzyme may be useful in treating dihydrotestosterone-related diseases such as prostate cancer and benign prostatic hyperplasia. Using an enzyme preparation obtained from human prostate carcinoma tissue, the inhibition values ranged from 0 to 57% at the given dose of 100 microM. In the series of free acids, surprisingly, the compounds showed only modest inhibitory potency (0-26%). By contrast, the ethyl esters displayed inhibition values up to 57%. Structure-activity relationships are discussed.

In vitro influence of plasma steroid-binding proteins on androgen metabolism in human leukocytes

The purpose of this study was to investigate the influence of plasma steroid-binding proteins on androgen metabolism in intact leukocytes prepared from normal male and female blood samples. Leukocyte preparations were incubated for 24 h at 37 degrees C with either labeled or unlabeled testosterone (T), 5 alpha-dihydrotestosterone (5 alpha-DHT), and androstenedione (A). After extraction, the formed labeled metabolites were first identified by high performance liquid chromatography, then, using unlabeled substrates, metabolite concentrations were measured by specific radioimmunoassays. The conversion ratios of substrate to metabolite were calculated for each preparation using either labeled or unlabeled substrates. In the absence of steroid-binding proteins, the mean conversion ratios of T to A, A to T, T to 5 alpha-DHT, and 5 alpha-DHT to 3 alpha-androstanediol (3 alpha-D) were, in males and females, respectively, 5.6% and 6.1% (n = 11), 5.6% and 5.6% (n = 5), 2.8% and 2.2% (n = 11), 43.1% and 40.0% (n = 5), these sex differences being non-significant. The presence of increasing amounts of plasma, purified albumin or sex hormone binding-globulin (SHBG) in the incubation media reduced metabolite formation dose-dependently. However, a 1000-fold greater concentration of albumin than of SHBG was necessary for 50% inhibition of androgen metabolism by leukocytes, showing SHBG to have the main protective effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional studies of 11 beta-hydroxysteroid dehydrogenase

11 beta-Hydroxysteroid dehydrogenase (11-HSD) catalyzes the interconversion of cortisol and cortisone. This activity is postulated to protect the type I (mineralocorticoid) receptor from excessive concentrations of cortisol, allowing aldosterone to function as a mineralocorticoid. An enzyme with 11-HSD activity was isolated from rat liver and the corresponding rat and human cDNA and genomic clones isolated. This enzyme is a member of the "short chain dehydrogenase" family. Using site-directed mutagenesis, it was demonstrated that two highly conserved residues, Tyr-179 and Lys-183, are required for enzymatic function. Elimination of the amino terminus or the two glycosylation sites also destroys enzymatic activity. This may be due to actual disruption of enzymatic function or to effects on intracellular localization or stability of the enzyme. Examination of patients with apparent mineralocorticoid excess, a syndrome of juvenile hypertension thought to represent 11-HSD deficiency, did not reveal any mutations in the gene for this enzyme. There is substantial evidence for a second 11-HSD isozyme with distinct kinetic properties that is expressed in the renal distal tubule and possibly other sites of mineralocorticoid action. Apparent mineralocorticoid excess may involve this enzyme.

Purification of testosterone 5 alpha-reductase from human prostate by a four-step chromatographic procedure

Nuclear membrane bound testosterone 5 alpha-reductase solubilized in active form from human prostatic tissue by 0.5% n-octyl beta-D-glucopyranoside was purified by a four-step chromatographic procedure including DEAE-Trisacryl ion exchange, hydroxylapatite adsorption, testosterone-Sepharose affinity and Sepharose 4B gel filtration. A purification of approximately 30-fold was achieved judging from the increase in the specific enzymatic activity. We have purified the acidic pH-optimum 5 alpha-reductase type 2 isoenzyme. The apparent molecular weight of the purified enzyme was estimated as 42,000 by SDS-PAGE. At the same time we isolated a 38 kDa protein characterized by a real affinity for testosterone and by a possible association to the 5 alpha-reductase enzyme.

5 alpha-reductase inhibition by finasteride (Proscar) in epithelium and stroma of human benign prostatic hyperplasia

Finasteride is a specific 5 alpha-reductase inhibitor that has been shown to reduce the size of human benign prostatic hyperplasia (BPH) by inhibiting the intraprostatic conversion of testosterone to 5 alpha-dihydrotestosterone. The aim of the present in vitro study was to describe in more detail the inhibitory effect of finasteride on 5 alpha-reductase in epithelium and stroma of human BPH. 5 alpha-Reductase activity in epithelium and stroma was inhibited dose-dependently by finasteride. The mean IC50 (50% inhibitory concentration) values, determined in the presence of various testosterone concentrations, were generally 2- to 4-fold lower in epithelium than in stroma. With finasteride concentrations greater than 5 nM, competitive inhibition of 5 alpha-reductase occurred both in epithelium and stroma. The mean inhibition constant Ki[nM +/- SEM] was 7 +/- 3 and 31 +/- 3 in epithelium and stroma, respectively. In the presence of finasteride concentrations < or = 5 nM, the epithelial 5 alpha-reductase seems to be inhibited in an uncompetitive manner, whereas such low finasteride concentrations cause either no inhibition (1-2 nM) or competitive inhibition (5 nM) in stroma. Our present study provides evidence that the inhibitory effect of finasteride on 5 alpha-reductase is much stronger in epithelium than in stroma. Therefore, it is conceivable that the global size-reduction of BPH under finasteride treatment is primarily due to the regression of BPH epithelium.

5 alpha-reductase inhibitors and prostatic disease

5 alpha-Reductase inhibitors are a new class of substances with very specific effects on type I and type II 5 alpha R which may be of use in the treatment of skin disease, such as male pattern baldness, male acne and hirsutism, as well as prostatic hyperplasia and prostate cancer. At least two types of 5 alpha R inhibitors with a different pH optimum have been described. cDNA encoding for both the type I and the type II enzyme has been cloned. Most of the orally effective 5 alpha R inhibitors belong to the class of 4-azasteroids. The radical substituted in the 17 position of the steroid ring seems to be related to species specific variations and to the types of 5 alpha R enzymes in different species and organ systems. 5 alpha R inhibitors lead to a decrease of plasma DHT by about 65% while there is a slight rise in plasma testosterone. The decrease of tissue DHT in the ventral prostate of the intact rat, the dog and in humans is more pronounced and amounts to about 85%. There is a reciprocal rise of tissue T in these systems. The application of an inhibitor of 5 alpha R type II leads to a shrinkage of BPH in men by about 30%. In the rat a similar shrinkage accompanied by a significant decrease of total organ DNA occurs. This decrease, however, is not as pronounced as can be achieved with castration.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of action of androgen in hair follicles

In order to investigate the mode of action of testosterone (T) on human hair follicles we studied the metabolism of T and localization of androgen receptors in outer root sheath cells (ORSC) and dermal papilla cells (DPC) from different body sites. T was principally metabolized to androstenedione (delta 4) even in beard ORSC as well as epidermal keratinocytes (EK), and the ratio of apparent 5 alpha-reductase (5 alpha-R) to 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) did not differ between these two kinds of cells. The 5 alpha-R activity in beard DPC was 3 times as high as that in occipital scalp and axillary DPC. The 5 alpha-R of beard DPC exhibited a narrow optimum pH of 5.5, which is characteristic of type 2 enzyme present in androgen target cells. In contrast, 5 alpha-R of DPC from axillary and occipital scalp hair showed a broad optimum pH range between 6.5-9.0 corresponding to type 1 5 alpha-R. Androgen receptors were detected in the DPC of beard and axillary hair follicles, but not in those of occipital scalp hair follicles using immunohistochemical staining with polyclonal anti-androgen receptor antibody. Epithelial cells of the hair bulb were not stained by the antibody. Androgen receptors were also detected in the nuclei of cultured beard and axillary DPC, but the DPC from occipital scalp hair follicles showed little staining with the antibody. We also examined the effects of T on the DNA synthesis and proliferation of cultured ORSC and DPC. T did not have a proliferative effect on either type of cell when cultured alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Male pseudohermaphroditism caused by mutations of testicular 17 beta-hydroxysteroid dehydrogenase 3

Defects in the conversion of androstenedione to testosterone in the fetal testes by the enzyme 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) give rise to genetic males with female external genitalia. We have used expression cloning to isolate cDNAs encoding a microsomal 17 beta-HSD type 3 isozyme that shares 23% sequence identity with other 17 beta-HSD enzymes, uses NADPh as a cofactor, and is expressed predominantly in the testes. The 17 beta HSD3 gene on chromosome 9q22 contains 11 exons. Four substitution and two splice junction mutations were identified in the 17 beta HSD3 genes of five unrelated male pseudohermaphrodites. The substitution mutations severely compromised the activity of the 17 beta-HSD type 3 isozyme.

Role of 5 alpha-reductase in health and disease

The mechanism of androgen action varies in different tissues, but in the majority of androgen target tissues either testosterone or 5 alpha-dihydrotestosterone (DHT) binds to a specific androgen receptor to form a complex that can regulate gene expression. Testosterone is metabolized to DHT by the enzyme 5 alpha-reductase. The autosomal recessive genetic disorder of 5 alpha-reductase deficiency has clearly shown that the requirement for DHT formation varies with different tissues. In this syndrome genetic males contain normal male internal structures including testes, but exhibit ambiguous or female external genitalia at birth; at puberty they undergo partial virilization which includes development of a male gender identity even if brought up as females. Their development suggests that testosterone itself is able to stimulate psychosexual behaviour, development of the embryonic wolffian duct, muscle development, voice deepening, spermatogenesis, and axillary and pubic hair growth; DHT seems to be essential for prostate development and growth, the development of the external genitalia and male patterns of facial and body hair growth or male-pattern baldness. How different hormones operate to regulate genes via the same receptor is currently unknown, but appears to involve cell-specific factors. The 5-alpha-reductase enzyme has proved difficult to isolate biochemically, but recently at least two human isoenzymes have been identified using molecular biological methods. All the various 5 alpha-reductase-deficient kindreds have been shown to have mutations in 5 alpha-reductase 2, the predominant form in the prostate. The biological role of 5 alpha-reductase 1 has not yet been ascertained, but at present it cannot be ruled out that some of the actions ascribed to testosterone are indeed in cells producing DHT via this enzyme. The activity of 5 alpha-reductase is also implicated in benign prostatic hypertrophy, hirsutism and possibly male-pattern baldness; recent evidence discounts the role of 5 alpha reductase 2 in sebaceous glands and acne. Specific inhibitors of both enzymes are now available and finasteride, a 5 alpha-reductase 2 inhibitor, has been used successfully in clinical trials of benign prostatic hypertrophy. Knowledge of 5 alpha-reductase is expanding dramatically at the moment with the application of molecular biological methods. The advent of antibodies to the isoenzymes should herald further understanding of their biological and clinical roles.

Progesterone 5-alpha-reduction in neuronal and in different types of glial cell cultures: type 1 and 2 astrocytes and oligodendrocytes

Progesterone, like testosterone, can be converted in the brain into 5-alpha-reduced metabolites (5-alpha-pregnan-3,20-dione, DHP; 5-alpha-pregnan-3-alpha-ol-20-one, THP). Recently we have shown that testosterone is 5-alpha-reduced to DHT mainly in neurons, while glial cells possess this enzymatic activity only in limited amounts. On the other hand, a glial cell type (type 1 astrocytes) is almost exclusively responsible for the further metabolism of DHT into 3-alpha-diol. The aim of the present studies was that of evaluating the formation of the 5-alpha-reduced metabolites of progesterone in cultures of neurons, type 1 and 2 astrocytes and oligodendrocytes. The data here presented indicate that, similarly to what happens when testosterone is used as the substrate, the 5-alpha-reductase which metabolizes progesterone shows a significantly higher activity in neurons than in glial cells; however, also type-1 and type-2 astrocytes as well as oligodendrocytes possess some ability to 5-alpha-reduce progesterone. On the contrary, the 3-alpha-hydroxysteroid dehydrogenase (3-alpha-HSD), the enzyme which converts DHP into THP, appears to be mainly present in type-1 astrocytes; much lower levels of this enzyme are present in neurons and in type-2 astrocytes. At variance with the previous results obtained utilizing androgens as precursors, oligodendrocytes show a considerable 3-alpha-HSD activity, even if this is statistically lower than that present in type-1 astrocytes. The existence of isoforms of the enzymes involved in androgen and progesterone metabolism may explain these data.

Inhibition of the activity of 'basic' 5 alpha-reductase (type 1) detected in DU 145 cells and expressed in insect cells

The purpose of this study was 2-fold: (1) to identify the 5 alpha-reductase (5 alpha-R) isozyme(s) present in DU 145 cells, a human cell-line of low androgen sensitivity derived from a cerebral metastasis of an epithelial prostate cancer; and (2) to compare the inhibitory potencies of three compounds on the 'basic' 5 alpha-R isozyme expressed in a baculovirus-directed insect cell system. Conversion of testosterone (T) into 5 alpha-dihydrotestosterone (DHT) in DU 145 cells was measured by HPLC coupled to a Flo-one HP radioactivity detector. DU 145 cells exhibited 5 alpha-R activity (21 pmol DHT/min/mg protein) at pH 7.4 which disappeared at pH 5.5 suggesting that, of the two genomically distinct human isozymes identified so far, type 1 5 alpha-R is expressed in DU 145 cells. This was confirmed by at least two observations: first, 5 alpha-R activity in DU 145 cells was inhibited with much higher potency by 4-MA than by finasteride which is known to be a very poor competitor of the 'basic' enzyme (IC50s = 2.8 +/- 0.2 and 264 +/- 55 nM, respectively). Second, only the type 1 5 alpha-R cDNA and not type 2 5 alpha-R cDNA hybridized with DU 145 RNA. A high potency differential was also recorded for the inhibition of 'basic' type 1 5 alpha-R expressed in a baculovirus-directed-insect cell system by these two compounds, 4-MA being considerably more active than finasteride (Ki = 8.4 +/- 2.3 and 330 +/- 9 nM, respectively). This inhibition was competitive. On the other hand, inhibition by an n-hexane lipid/sterol extract of Serenoa repens (LSESr) was non-competitive and, when expressed in terms of recommended therapeutic doses, was 3-fold greater for LSESr than for finasteride. These studies suggest that LSESr might exert a regulatory inhibitory activity due to its specific lipid/sterol composition.

Genetic analysis of 11 beta-hydroxysteroid dehydrogenase

11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) catalyzes the interconversion of cortisol and cortisone. This activity is postulated to protect the Type I (mineralocorticoid) receptor from excessive concentrations of cortisol, allowing aldosterone to function as a mineralocorticoid. An enzyme with 11 beta-OHSD activity was isolated from rat liver and the corresponding rat and human cDNA and genomic clones isolated. This enzyme is a member of the short-chain dehydrogenase family. Using site-directed mutagenesis, it was demonstrated that the amino terminus and two highly conserved residues, Tyr-179 and Lys-183, are required for enzymatic function. Examination of patients with apparent mineralocorticoid excess, a syndrome of juvenile hypertension thought to represent 11 beta-OHSD deficiency, did not reveal any mutations in the HSD11 gene. This disorder may involve an additional enzyme with 11 beta-OHSD activity or possibly another cortisol metabolizing enzyme.

Endocrine properties of the testosterone 5 alpha-reductase inhibitor turosteride (FCE 26073)

Turosteride was tested in a series of studies for its effect on 5 alpha-reductase and for its possible influence on other steroidogenic enzymes and on steroid receptors. The compound was found to inhibit human and rat prostatic 5 alpha-reductases with IC50 values of 55 and 53 nM, respectively, whereas it caused a less marked inhibition of the dog enzyme (IC50 2.2 microM). Turosteride showed no relevant effect on rat adrenal C20,22-desmolase (IC50 254 microM) and human placental aromatase (IC50 > 100 microM), and only at relatively high concentrations it caused inhibition of human placental 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase (3 beta-HSD-I) (IC50 2.5 microM). Turosteride was found to be a selective 5 alpha-reductase inhibitor showing no noteworthy binding to receptors for androgens (relative binding affinity, RBA, 0.004%), estrogens (< or = 0.005%), progesterone (< 0.005%), glucocorticoids (< 0.01%) and mineralocorticoids (< 0.03%). Its biochemical profile was similar to that of finasteride, whereas 4-MA (17 beta-N,N-diethyl-carbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one) was confirmed to be a non-selective 5 alpha-reductase inhibitor, showing a degree of binding affinity to the androgen receptor (RBA 0.1%) and a marked inhibition of 3 beta-HSD-I (IC50 32 nM). When given orally in immature castrated rats together with subcutaneous testosterone propionate (TP) for 7 consecutive days, turosteride reduced the ventral prostate and seminal vesicle growth promoting effect of TP, with IC50 values of approximately 5 and 6.7 mg/kg/day, whereas levator ani weight was unchanged. In comparison, 4-MA was approx. 3-fold less potent than turosteride in reducing the prostate and seminal vesicle weights and caused a marked reduction of levator ani weight, thus showing its unselectivity.

Male sex determination: current concepts of male sexual differentiation

In order for an infant to develop as a phenotypically complete male or female, a cascade of complex molecular and morphological events must occur at the appropriate time and in the correct sequence during ontogeny. The male embryo's genetic sex is determined by its chromosomal constituents, the most important of which is the sex-determining gene, or testis-determining factor (TDF), on the Y chromosome. Male gonadal sex, or testis formation, is subsequently thought to be determined by this gene and by other secondary pathways. The male gonad, in turn, normally produces hormones such as testosterone and Mullerian inhibiting substance (MIS) that regulate differentiation of the internal and external genitalia, thus determining phenotypic sex. When an abnormality develops in any of the above three processes, an intersex infant with ambiguous genitalia results from the incongruent genetic, gonadal, and phenotypic sex. Clinically, such 46XY males with intersex abnormalities present challenges for gender assignment, timely surgical intervention, and appropriate hormonal therapy.

Characterization, expression, and immunohistochemical localization of 5 alpha-reductase in human skin

Human skin has been shown to contain a high level of 5 alpha-reductase activity, the enzyme that catalyses the conversion of the weak androgen testosterone into dihydrotestosterone, the most potent androgen. Because two types of 5 alpha-reductase genes have been characterized in humans, we have cloned 5 alpha-reductase cDNAs from adult human keratinocyte and skin fibroblast cDNA libraries to identify and gain better knowledge of the 5 alpha-reductase expressed in normal human skin. Nucleotide sequence analysis shows that the clones obtained correspond to the type I 5 alpha-reductase. RNase protection analysis using (poly A)+ RNA obtained from human skin and prostate also confirms that type I 5 alpha-reductase is the predominant type expressed in normal skin, whereas type II 5 alpha-reductase is the major form found in the prostate. Following polymerase chain reaction amplification of human keratinocyte and skin fibroblast cDNA, a low level of type II 5 alpha-reductase cDNA has been detected. Using antipeptide antibodies raised in rabbits against the peptide sequence covering amino acids 227 -240 to perform immunohistochemical localization of 5 alpha-reductase, we have found that 5 alpha-reductase is distributed in sweat and sebaceous glands, as well as in the epidermal cell layers, thus providing the basis for the important role of androgens in human skin and its appendages.