Role of steroid 5 alpha-reductase activity in sexual differentiation of the guinea pig.

The possible role of 5 alpha-reduction of steroids in the sexual differentiation of guinea pigs was determined by treating pregnant guinea pigs with a 5 alpha-reductase activity (5 alpha RA) inhibitor (17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstan-3-one, 4MA, 10 mg/day) from day 30 to 55 of gestation. 5 alpha RA in fetal diencephalon tissue obtained from 4MA-treated mothers on day 55 of gestation was suppressed compared to that of control tissue. Four litters receiving 4MA were carried to term along with an equal number of litters receiving the vehicle alone. Males that received 4MA in utero (n = 6) had altered external genitalia, i.e., hypospadias and reduced anogenital distances, but their adult copulatory behavior did not differ from that of controls (n = 7). In order to evaluate treatment effects on the hypothalamic-pituitary axis, all animals were challenged with estradiol benzoate (EB, 10 micrograms in oil, s.c.) 2 weeks after gonadectomy. Serial plasma samples were obtained and analyzed for luteinizing hormone (LH) using an heterologous radioimmunoassay. Control females (n = 13) and 4MA-treated females (n = 5) released LH in surge quantities about 42 h after EB treatment. Plasma from 4MA-treated females differed from controls in that it contained greater overall quantities of LH (p less than 0.05) and greater amounts at the time of the LH surge (p less than 0.05). Regardless of treatment males did not respond to EB.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of aging on kinetic parameters of 5 alpha-reductase in epithelium and stroma of normal and hyperplastic human prostate.

Altered 5 alpha-dihydrotestosterone (DHT) metabolism and stromal-epithelial cell interactions are two factors hypothesized to explain the development of benign prostatic hyperplasia (BPH). Furthermore, the development of BPH is clearly age dependent. Therefore, we studied the age-dependent alteration of 5 alpha-reductase, the enzyme that catalyzes the irreversible conversion of testosterone to DHT in epithelium and stroma of the human prostate. For this purpose kinetic parameters [Km Vmax] of 5 alpha-reductase were determined separately in epithelium and stroma of normal prostatic tissue (NPR) from 5 and BPH tissue from 20 men, and the results were correlated with the age of the donors (15-86 yr). The mean Km in epithelium [NPR, 14.3 +/- 1.8 (+/- SE); BPH, 29.5 +/- 2.7 nmol/L] was significantly (P less than 0.0001) lower than that in stroma (NPR, 78.4 +/- 8.5; BPH, 185.8 +/- 13.6 nmol/L). The mean Vmax in epithelium [NPR, 23.8 +/- 3.9 (+/- SE); BPH, 27.9 +/- 3.0 pmol/mg protein.h] was significantly (P less than 0.0001) lower than that in stroma (NPR, 68.3 +/- 4.4; BPH, 173.8 +/- 12.2 pmol/mg protein.h). The DHT-forming index (Vmax/Km) in NPR epithelium [1.6 +/- 0.2 (+/- SE)] was significantly (P less than 0.01) higher than that in NPR stroma (0.9 +/- 0.1), while in BPH the DHT-forming index was nearly identical in epithelium (1.1 +/- 0.1) and stroma (1.0 +/- 0.1). The Km values in epithelium and stroma both correlated positively (P less than 0.01) with age, but the Vmax values correlated positively with age (P less than 0.0001) only in stroma. The DHT-forming index decreased significantly with age in epithelium (P less than 0.01), but remained constant in stroma. These results indicate that there is a nonuniform age-dependent alteration of Km and Vmax in epithelium and stroma of the human prostate independent of the presence of BPH, which might have an impact on the conversion rate of testosterone to DHT with advancing age.

Reductive metabolism of 5 alpha-dihydrotestosterone by rat ventral and dorsolateral prostate: kinetic parameters of the enzymes.

In male sex accessory organs the active androgen 5 alpha-dihydrotestosterone (DHT) is metabolized to 5 alpha-androstane-3 alpha, 17 beta-diol (3 alpha-diol) and 5 alpha-androstane-3 beta, 17 beta-diol (3 beta-diol) by the reductase activities of 3 alpha-hydroxysteroid oxidoreductase (3 alpha-HSOR; EC 1.1.1.50) and 3 beta-hydroxysteroid oxidoreductase (3 beta-HSOR; EC 1.1.1.51). After separation of radiosubstrate and products by HPLC, these enzymes activities in subcellular preparations of rat ventral and dorsolateral prostate were determined from the conversion of [3H]DHT to the radiometabolites 3 alpha-diol and 3 beta-diol and 3 beta-triols (5 alpha-androstane-3 beta, 6 alpha, 17 beta-triol plus 5 alpha-androstane-3 beta, 7 alpha, 17 beta-triol). Whereas both enzymes were found in the dorsolateral prostate, 3 beta-HSOR reductase activity was near the limit of detection in ventral prostate. Unlike the equal distribution of 3 alpha-HSOR reductase between the microsomal and cytosol fractions of the ventral prostate, both 3 alpha- and 3 beta-HSOR reductase activities of the dorsolateral prostate are mainly confined to its cytosol fraction. Km and Vmax of the 3 alpha- and 3 beta-HSOR reductases in dorsolateral prostate cytosol were 1.8 microM, 24.6 pmol.mg-1 min-1 and 25.4 microM, 45.7 pmol.mg-1 min-1, respectively. We surmise from these and earlier studies that 3 beta-HSOR reductase is the rate-limiting prostatic enzyme in the catabolic disposition of intracellular DHT.

5 alpha-dihydrotestosterone formation is necessary for embryogenesis of the rat prostate.

To determine the role of 5 alpha-dihydrotestosterone (DHT; 17 beta-hydroxy-5 alpha-androstan-3-one) in formation of the embryonic prostate, we quantitated prostatic development in urogenital tracts of control male newborn and offspring of rats treated with a specific 5 alpha-reductase inhibitor (L652,931; Merck, Sharp, and Dohme) during prostate morphogenesis. Treatment with the 5 alpha-reductase inhibitor (50 mg/kg.day) from days 14-22 of gestation impaired development of the prostate and virilization of the external genitalia in male offspring compared to those in control animals. However, virilization of the internal genitalia (seminal vesicles, epididymis) was unaffected. Simultaneous administration of DHT (50 mg/kg.day) with the 5 alpha-reductase inhibitor restored prostate development and anogenital distances of males to normal and virilized the external genitalia of females. We conclude that DHT is the active androgen responsible for prostatic development in the rat.

Androgen metabolism in the male hamster--1. Metabolism of testosterone in the pituitary gland and in the brain of animals exposed to different photoperiods.

It is known that the metabolism of testosterone in the brain and in the anterior pituitary is different in mammalian and in photoperiodic avian species. In many mammalian species, testosterone is mainly metabolized to 5-alpha-reduced compounds (e.g. 17-beta-hydroxy-5-alpha-androstan- 3-one, 5 alpha-DHT and 3-alpha,17-beta-dihydroxy-5-alpha-androstane, 5-alpha,3-alpha-diol) and, to a smaller extent, to 4-androstene-3,17-dione (androstenedione), while in birds, androstenedione is the main testosterone metabolite and the conversion to the 5-alpha-reduced compounds is quantitatively negligible. In avian species, testosterone is also converted to 5-beta-reduced steroids (mainly 17-beta-hydroxy-5-beta-androstan-3-one, 5-beta-DHT and 3-alpha,17-beta-dihydroxy-5-beta-androstane, 5-beta,3-alpha-diol), and there is also evidence that in these species testosterone metabolism in the central structures may be influenced by the photoperiod. Since the hamster is a mammal whose reproductive cycle is controlled by day length, it has been analyzed whether: (a) the central structures of the hamster (cerebral cortex, hypothalamus and anterior pituitary) metabolize testosterone in vitro following a mammalian (5-alpha-reduced derivatives) or an avian (androstenedione and 5-beta-reduced compounds) pattern; and (b) the metabolism of testosterone in the same structures may be modified by the exposure to different photoperiods (LD 14:10 or LD 8:16). The present data indicate that no one of the hamster structures examined produces the 5-beta-reduced derivatives. Moreover, the formation of the 5 alpha-DHT is quantitatively low, and is not affected by the photoperiod. In contrast, androstenedione is formed in quite high yields and the exposure of the animals to 60 days of short photostimulation increases the formation of this steroid in the pituitary gland, but not in the brain structures. From these data, it appears that the central structures of the hamster metabolize testosterone with a pattern which is intermediate between that of birds and mammals.

Differential distribution of the 5-alpha-reductase in the central nervous system of the rat and the mouse: are the white matter structures of the brain target tissue for testosterone action?

In the brain of several animal species testosterone is converted into a series of 5-alpha-reduced metabolites, and especially into 17-beta-hydroxy-5-alpha-androstan-3-one (DHT), by the action of the enzyme 5-alpha-reductase. The formation of DHT has never been evaluated in the white matter structures of the brain, which are composed mainly of myelinated axons. The experiments here described were performed in order to study, in the rat and the mouse, the DHT forming activity of several white matter structures, in comparison with that of the cerebral cortex and of the hypothalamus. Two sampling techniques were used in the rat: microdissection under a stereo-microscope from frozen brain sections of fragments of corpus callosum, optic chiasm and cerebral cortex; fresh tissue macrodissection of subcortical white matter, cerebral cortex and hypothalamus. Only macrodissection was used in the mice. The data show that, independently from the sampling technique used, there are considerable quantitative differences in the distribution pattern of the 5-alpha-reductase activity within different brain structures. Both in the rat and in the mouse, the enzyme appears to be present in higher concentrations in the white matter structures, than in the cerebral cortex and in the hypothalamus. The present results clearly show that the subcortical white matter and the corpus callosum are at least three times as potent as the cerebral cortex in converting testosterone into DHT. An even higher 5-alpha-reductase activity has been found in the optic chiasm. Further work is needed in order to understand the possible physiological role of DHT formation in the white matter structures.

Effect of antiandrogen and/or antiestrogen blockade on human prostate epithelial and stromal cell protein synthesis.

To evaluate the role of small amounts of DHT in prostate tissue as a stimulus to epithelial cell growth (protein synthesis) we studied tissue from patients given various androgen-blocking drugs prior to transurethral resection of the prostate (TURP) and measured epithelial protein synthesis and DHT in the tissue specimens. We also studied the effects on stromal cell protein synthesis of an antiestrogen, tamoxifen. Test drugs prior to TURP included Megace 160 mg per day, Megace 160 mg per day plus Tamoxifen 40 mg per day, Megace 160 mg a day plus ketoconazole 1200 mg per day and tamoxifen 40 mg/day. The tissue was processed immediately and epithelial and stromal cells separated by digestion of tissue with 0.5% collagenase. After separation, epithelial cells were labeled with either [3H]leucine or L-[35S]methionine. Stromal cells were labelled with [3H]proline. DHT was measured in whole prostate tissue. Megace alone and Megace plus tamoxifen significantly decreased both [3H]leucine incorporation into protein and tissue concentration of DHT; Megace plus ketoconazole significantly decreased L-[35S]methionine incorporation into protein and DHT. Tamoxifen significantly decreased stromal protein synthesis. When the data correlating DHT with epithelial protein synthesis using both labeling techniques were combined, the curves were parallel and a strong correlation was noted between DHT and protein synthesis over a wide range of values (P less than 0.001). These results suggest that in hormone-dependent prostate cancer even small amounts of prostate DHT such as may occur from adrenal androgens following castration may significantly stimulate growth of the tumor epithelial cells. Since tamoxifen decreased stromal protein synthesis, estrogen is likely a significant growth stimulus to the increased stromal mass characteristic of benign prostatic hypertrophy.

Functional characteristics of nuclear 5 alpha-reductase from rat ventral prostate.

The subcellular distribution and functional characteristics of 5 alpha-reductase (3-oxo-5 alpha-steroid: NADP+ 4-ene-oxidoreductase, EC 1.3.1.22) from rat ventral prostate were studied and compared to the 5 alpha-reductase from female rat liver. Tissue fractionation retained main enzymic activity in the microsomal fraction of rat liver, while 5 alpha-reductase from rat prostate was localized in the nuclear membrane with a specific activity 160 times that of the initial homogenate. The purity of nuclear envelopes was checked by electron microscopy. Solubilization experiments indicated that the hepatic 5 alpha-reductase is attached to the endoplasmic reticulum as a peripheral protein, while the nuclear prostatic enzyme is an integral membrane protein. Incubation experiments with phospholipases suggested a decisive role of the surrounding phospholipids for the prostatic enzyme activity. To elucidate the characteristics of hydrogen transfer of the enzyme, the effect of flavins and different other cofactors on 5 alpha-reductase activity in isolated prostatic nuclei were studied. Our findings indicate that in rat ventral prostate the conversion of testosterone to 5 alpha-dihydrotestosterone proceeds by a direct hydrogen transfer from NADPH to testosterone. Concerning these parameters the behaviour of hepatic 5 alpha-reductase is absolutely different from the prostatic enzyme. The localization of 5 alpha-reductase within the nuclear envelope of rat ventral prostate as an integral membrane protein seems to be of physiological significance with regard to the action of androgens.

Epidermal keratinocytes: a source of 5 alpha-dihydrotestosterone production in human skin.

The major products of testosterone, androstenedione, and progesterone metabolism by human epidermal keratinocytes are 5 alpha-reduced steroids, viz. 5 alpha-dihydrotestosterone, 5 alpha-androstanedione, and 5 alpha-dihydroprogesterone, respectively. The rates of metabolite formation by these cells were linear with incubation time up to 3 h. The apparent Km of keratinocyte 5 alpha-reductase was 1.3 microM for androstenedione and 1.5 microM for progesterone. 5 alpha-Reductase activity was found only in particulate subcellular fractions of a homogenate of epidermal keratinocytes when assayed with tritium-labeled progesterone as the substrate and NADPH as the cofactor. In addition to 5 alpha-reductase activity, other enzymatic activities found in epidermal keratinocytes were 17 beta-hydroxysteroid oxidoreductase and 3 beta-hydroxysteroid oxidoreductase. These enzymes were expressed in the formation of androstenedione from testosterone, testosterone from androstenedione, isoandrosterone from androstenedione, and 3 beta-hydroxy-5 alpha-pregnan-20-one from progesterone. The apparent Km of 17 beta-hydroxysteroid oxidoreductase for androstenedione in epidermal keratinocytes was 10 microM. When measured at weekly intervals, the rates of product formation from testosterone, androstenedione, or progesterone by cultured epidermal keratinocytes increased several-fold with advancing time in culture up to 3 weeks. The results of these studies suggest that epidermal keratinocytes are a major site of synthesis of biologically potent androgens in human skin, viz. testosterone from androstenedione and 5 alpha-dihydrotestosterone from testosterone. Skin is a target organ for 5 alpha-dihydrotestosterone action, and thus, the local formation of 5 alpha-dihydrotestosterone may play an important role in the regulation of proliferation and differentiation of keratinocytes.

Preoptic formation of 17 beta-oestradiol is influenced by behavioural stimuli in the dove.

In vitro study of testosterone (T) metabolism shows that formation of 17 beta-oestradiol (E2) in the preoptic area is higher in male doves exposed to behavioural stimuli from interacting pairs than in visually isolated males or males that have interacted with females. Formation of 5 alpha-dihydrotestosterone, 5 beta-dihydrotestosterone and 5 beta-androstane-3 alpha, 17 beta-diol was similar in all groups, indicating that exposure to stimuli from interacting pairs influences aromatization of T and not other pathways of androgen metabolism. The results suggest that sexual stimuli, which do not involve tactile contact between male and female, affect local E2 formation in the brain.

Adrenal androgen blockade in relapsed prostate cancer.

The effectiveness of aminoglutethimide as an adrenal inhibitor has been well-documented by decreases in plasma testosterone and delta 4 levels, which fall significantly following the drug in previously orchiectomized patients. The use of cortisone or cortisol along with aminoglutethimide complicates the interpretation of the role of aminoglutethimide in effecting clinical responses. However, since physiologic replacement doses were used in most cases, a significant role for cortisone in effecting a clinical response is unlikely. Aminoglutethimide does have side-effects including rash and lethargy. It requires administration of replacement doses of cortisone and sometimes mineralocorticoid as well since it inhibits adrenal steroid synthesis in all pathways. Peripheral adrenal androgen inhibitors, such as flutamide, Megace, cyproterone acetate or 5 alpha-reductase inhibitors, in the future may be equally effective and simpler to administer than aminoglutethimide but objective and adequate numbers of studies using acceptable objective criteria must be done in order to adequately compare these drugs to aminoglutethimide. There appears to be approximately a 33% response rate (partial objective regression and objectively stable) following blockade of adrenal androgens in patients in relapse after castration. Blockade of adrenal androgen is certainly more tolerable and has many fewer side-effects than the alternative of chemotherapy which does not give response rates in most cases that are significantly different from those noted with aminoglutethimide. Murray's paper, combined with prior studies by Drago et al., goes a long way in establishing adrenal androgen blockade with that drug as the next step to be taken in patients following relapse from prior castration (medical or surgical). The most important question revolves around the timing of adrenal androgen blockade. As stated by Murray, will adrenal androgen blockade provide better survival if given earlier following relapse? The answer is not known yet. The answer may come from the work of Labrie [1], Geller and Albert [2] and others, who suggest that total survival in prostate cancer may be improved with blockade of adrenal androgens not after relapse following castration, but with panandrogen blockade at the time of initial therapy for prostate cancer.

Changes in ovarian steroidogenesis in prepuberal rats induced to ovulate by low doses of human chorionic gonadotrophin.

To determine whether the decrease in ovarian 5 alpha-reduced androgen production before first ovulation might be caused by an increase in serum LH, prepuberal female rats were injected at 28-31 days of age with low doses of human chorionic gonadotrophin (hCG) (0.05-0.075 i.u., four times daily). This treatment resulted in ovulation of six to ten ova per rat on day 32 in all animals. Treatment with hCG resulted in a gradual decrease in ovarian content and production (i.e. content in ovary and medium after 4h of incubation) of 5 alpha-dihydrotestosterone (DHT) and 5 alpha-androstane-3 alpha, 17 beta-diol. The ovarian content of DHT and the production of 5 alpha-androstane-3 alpha, 17 beta-diol decreased within 24 h after the first injection of hCG. Oestradiol content and production increased between 24 and 48 h after the start of treatment and was maximal on day 31 (day of pro-oestrus). Activities of 5 alpha-reductase and aromatase were measured in ovarian homogenates obtained on days 29-31. Activity of 5 alpha-reductase in hCG-treated rats was lower than that in control rats on all days studied. Aromatase activity in hCG-treated rats increased between days 29 and 31. It was concluded that multiple injections of low doses of hCG, which may induce ovulation, cause a decrease in 5 alpha-reduced androgen production, which is probably due to a decrease in 5 alpha-reductase activity. The subsequent increase in oestradiol production corresponds with an increase in aromatase activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Production and metabolism of dihydrotestosterone in peripheral tissues.

The production and metabolism of dihydrotestosterone (DHT) was studied in 10 normal men using constant infusions of [7-3H]-delta 4 -androstenedione (A)/[4-14C]DHT (6 men) or of [7-3H]testosterone (T)/[4-14C]DHT (4 men) with measurement of radioactivity as precursor and product in the brachial artery, and a superficial vein (draining primarily adipose tissue) and deep vein (draining primarily muscle) in the arm opposite to the infusion. The metabolic clearance rates (MCR) were (mean +/- SE) 560 +/- 55, 1620 +/- 80, and 790 +/- 65, 1/day for DHT, A and T respectively. The overall conversions (percent of A or T infused which was measured as DHT in arterial blood) were 2.3 +/- 0.8% and 2.7 +/- 0.5% for A to DHT and T to DHT. Of the DHT entering the adipose tissue 13.8 +/- 3.4% was metabolized and of that entering muscle 5.8 +/- 1.8% was metabolized. On the basis of assumed blood flows, adipose tissue and muscle metabolism each carry out approx. 7-8% of the overall metabolism of DHT. Of the A entering the forearm adipose tissue 1.9 +/- 0.5% was converted to DHT. Extrapolated to the body's adipose tissue, this represents 14% of the total A converted to DHT. Of the T entering the forearm adipose tissue 1.2 +/- 0.3% was converted to DHT. Extrapolated to the body's adipose tissue, this represents 6% of the total T converted to DHT. In three out of six subjects infused with A/DHT and in three out of four subjects infused with T/DHT small gradients indicating conversion of A and T to DHT by tissues drained by the deep vein were found. The mean value for the conversion of A to DHT across the deep vein tissues was 0.84 +/- 0.51% and for T to DHT was 0.28 +/- 0.12%. Both adipose tissue and muscle metabolize DHT but only adipose tissue appears to play a role in the conversion of A and T to DHT.

Correlated biochemical and stereological studies on testosterone metabolism in the stromal and epithelial compartment of human benign prostatic hyperplasia.

The growth and function of the human prostate is dependent upon a continuous supply of androgens, mainly 5 alpha-dihydrotestosterone, the 5 alpha-reduced metabolite of testosterone. Within the human prostate dihydrotestosterone is thought to be the intracellular mediator of androgen action. Although it is well documented that dihydrotestosterone is evenly distributed between the stromal and epithelial compartment of the prostate, the anatomical localization of dihydrotestosterone formation within the normal and hyperplastic prostate is still not established. To provide further insight into this problem we have measured, under conditions approximating the in vivo state, dihydrotestosterone formation in prostates obtained from 4 men with normal prostates and 36 men with benign prostatic hyperplasia. In addition to this we have performed histometric analysis of the cellular composition of the samples incubated, in order to correlate the morphological and the histochemical findings. Dihydrotestosterone is the major metabolite, and androstanediol and androstenedione were formed in smaller quantities. Under the given conditions metabolite formation from testosterone increased linearly for 60 minutes and the half maximum rate of dihydrotestosterone formation (Km) was observed at about 1.25 X 10(-6) M testosterone, a value similar to that reported for rat prostatic nuclei and human prostatic tissue. Dihydrotestosterone formation was higher in hyperplastic prostates than in the normal prostate. (Student's t test: p less than 0.05). The stroma in both the normal and hyperplastic tissue converts testosterone to dihydrotestosterone very actively. No significant relation was found between dihydrotestosterone formation and the per cent distribution of the stromal and epithelial compartment in any sample studied. In conclusion, our results are compatible first with the thesis that the rate of dihydrotestosterone formation is increased in the hyperplastic prostate and secondly with the concept that the rate of dihydrotestosterone formation is approximately the same in the epithelial and stromal compartments of the prostate.

The relationship between growth and androstenedione metabolism in four cell lines of human breast carcinoma cells in culture.

The conversion of androstenedione (A) to estrogens, testosterone (T) and 5 alpha-reduced metabolites was studied in different phases of cell growth in 4 lines of cultured human breast carcinoma cells. Aromatase activity was 10-fold greater in MD and DM than in MCF7 cells and was undetectable in ZR75 cells. Estrogen formation in MD and DM lines increased during the phase of exponential growth and decreased to 20% of maximum during confluence. 5 alpha-Reductase activity was determined by the formation of 5 alpha-androstane-3,17-dione (5 alpha-A-dione) and androsterone (AND), and was 5-fold greater in ZR75 cells than MD cells and 2-fold greater than in MCF7 cells. This activity was relatively constant during exponential growth and decreased during confluence. T accumulation was inversely related to 5 alpha-reductase activity. The MCF7 and ZR75 cells which contain estrogen receptors had the highest levels of 5 alpha-reductase activity while the MD line which lacks estrogen receptors had the lowest 5 alpha-reductase activity. The assessment of aromatase and 5 alpha-reductase activity in addition to estrogen and progesterone receptors may be helpful in predicting hormone sensitivity in human breast tumours.

Testosterone metabolism in the uropygial gland of the quail.

The metabolism of testosterone in the uropygial gland of the quail principally results in the production of 17 alpha, 5 beta derivatives. Moreover, an unusually small amount of testosterone is converted to 5 alpha-dihydrotestosterone. These results question the role played by intracellular 5 alpha-reduction in the response of the gland to testosterone stimulation.

Endocrine and biochemical studies in a 46,XY phenotypically male infant with 17-ketosteroid reductase deficiency.

A 46,XY phenotypically male patient with 17-ketosteroid reductase deficiency is described. The patient was a 6-month-old infant who presented with micropenis and bilateral cryptorchidism. Baseline plasma levels of testosterone (T), delta 4-androstenedione (delta 4A), and 5 alpha-dihydrotestosterone (5 alpha-DHT) were within the normal range [patient: 0.17 (T), 0.12 (delta 4A), and 0.032 (5 alpha-DHT) ng/ml; normal infants: 0.03-0.55 (T), 0.14-0.45 (delta 4A), and 0.01-0.23 (5 alpha-DHT) ng/ml]. hCG administration induced a significant rise in plasma delta 4A levels (up to 8.39 ng/ml) and a slight increase in T and 5 alpha-DHT levels. The delta 4A/T ratios before and during the hCG challenge were 0.86 and 55.61, respectively (controls: 0.83 and 0.13). Incubation of genital skin-derived fibroblasts from the patient with either [3H]T or [3H] delta 4A revealed normal formation of delta 4A from T and diminished conversion of delta 4A to T. The development of a male phenotype despite both a testicular and peripheral 17-ketosteroid reductase deficiency is difficult to explain. It is possible that the fetal testes were the source of sufficient amounts of T during the early periods of embryonic life, and that late onset of the enzyme deficiency prevented the development of completely normal male genitalia. The in vitro finding of normal T to delta 4A conversion by the mutant fibroblasts suggests that in this particular tissue 17 beta-reduction and dehydrogenation of androgens are mediated by two isoenzymes with distinct substrate and/or cofactor specificities.

A new dihydrotestosterone-forming index (DHTi).

A new index (DHTi) for the net formation of dihydrotestosterone (DHT) in a specific tissue is presented. This index is based on the main metabolic pathways forming DHT as well as on the main enzymatic activities removing DHT from the tissue. In the rat prostate, the DHTi is different in the various prostatic lobes. The index is highest in the ventral prostatic lobe, intermediate in the dorsal prostate and coagulating gland, and very low or undetectable in the seminal vesicles and the lateral prostatic lobe. With increasing age of the rats, the DHTi decreased. Testosterone treatment to old rats leads to an increased index.