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

Comparison of Serenoa repens With Tamsulosin in the Treatment of Benign Prostatic Hyperplasia: A Systematic Review and Meta-Analysis

Studies reported that Serenoa repens was effective in relieving lower urinary tract symptoms (LUTS). This article carried out a systematic review and meta-analysis to compare Serenoa repens with tamsulosin in the treatment of benign prostatic hyperplasia (BPH) after at least 6-month treatment cycle. Four studies involving 1,080 patients (543 in the Serenoa repens group and 537 in the tamsulosin group) were included in the meta-analysis. The results were as follows: compared with tamsulosin, Serenoa repens had a same effect in treating BPH in terms of International Prostate Symptom Score (IPSS) (mean difference [MD] 0.63, 95% confidence interval [CI] [−0.33, 1.59], p = 0.20), quality of life (QoL) (MD 1.51, 95% CI [−1.51, 4.52], p = 0.33), maximum flow rate (Qmax) (MD 0.27, 95% CI [−0.15, 0.68], p = 0.21), postvoid residual volume (PVR) (MD −4.23, 95% CI [−22.97, 14.44], p = 0.65), prostate-specific antigen (PSA) (MD 0.46, 95% CI [−0.06, 0.97], p = 0.08) with the exception of prostate volume (PV) (MD −0.29, 95% CI [−0.41, −0.17], p < 0.00001). For side effects, Serenoa repens was well tolerated compared with tamsulosin especially in ejaculation disorders (odds ratio [OR] = 12.56, 95% CI [3.83, 41.18], p < 0.0001) and decreased libido (OR = 5.40; 95% CI [1.17, 24.87]; p = 0.03). This study indicated that Serenoa repens had the same effect in treating BPH compared with tamsulosin in terms of IPSS, QoL, and PVR after at least 6-month treatment cycle, however, the latter had a greater improvement in PV compared with the former. And Serenoa repens did not increase the risk of adverse events especially with respect to ejaculation disorders and libido decrease.

Recent Advances in Drug Design and Drug Discovery for Androgen- Dependent Diseases

This article summarizes the importance of different targets such as 5α-reductase, 17β-HSD, CYP17A, androgen receptor and protein kinase A for the treatment of prostate cancer and benign prostatic hyperplasia. It is a well known fact that dihydrotestosterone (DHT) is associated with the development of androgen-dependent afflictions. At the present time, several research groups are attempting to develop new steroidal and non-steroidal molecules with the purpose of inhibiting the synthesis and biological response of DHT. This review also discusses the most recent studies reported in the literature that describe the therapeutic potential of novel compounds, as well as the new drugs, principally inhibitors of 5α-reductase.

A prospective study of the efficacy of Serenoa repens, Tamsulosin, and Serenoa repens plus Tamsulosin treatment for patients with benign prostate hyperplasia

INTRODUCTION

Increasing attention has been focused on the use of phytotherapeutic agents to alleviate the symptoms of benign prostatic hyperplasia (BPH) in recent times. The best described and studied phytotherapeutic agent is Serenoa repens (SR).

MATERIALS AND METHODS

This prospective study was designed to have 3 arms including SR 320 mg per day (N = 20), Tamsulosin (TAM) 0.4 mg per day (N = 20) and SR + TAM (N = 20) to reveal the superiority or equivalence between these treatment regimens in BPH.

RESULTS

The groups were not statistically different with regard to increase in maximal urinary flow rate (Q (max)) and decrease in International Prostate Symptom Score (I-PSS) (P > 0.05). No adverse effect was detected in SR therapy group.

CONCLUSION

Treatment of BPH by both SR and TAM seems to be effective alone. None of them had superiority to another and additionally, combined therapy (SR + TAM) does not provide extra benefits. Furthermore SR is a well-tolerated agent that can be used alternatively in the treatment of LUTS due to BPH.

Estrogens and Antiestrogens as Etiological Factors and Therapeutics for Prostate Cancer

Mounting evidence supports a key role played by estrogen or estrogen in synergy with an androgen, in the pathogenesis of prostate cancer (PCa). New experimental data suggest that this process could begin as early as prenatal life. During adulthood, estrogen carcinogenicity is believed to be mediated by the combined effects of hormone-induced, unscheduled cell proliferation and bioactivation of estrogens to genotoxic carcinogens. Increased bioavailability of estrogen through age-dependent increases in conversion from androgen could also be a contributing factor. Individual variations and race-/ethnic-based differences in circulating or locally formed estrogens or in tissue estrogen responsiveness may explain differential PCa risk among individuals or different populations. Estrogen receptor (ER)-alpha and ER-beta are the main mediators of estrogen action in the prostate. However, ER-beta is the first ER subtype expressed in the fetal prostate. During cancer development, ER-beta expression is first lost as tumors progress into high grade in the primary site. Yet, its reexpression occurs in all metastatic cases of PCa. A change in cytosine methylation in a regulatory CpG island located in the proximal promoter of ER-beta may constitute an "on/off" switch for reversible regulation of ER-beta expression. A variety of estrogenic/antiestrogenic/selective estrogen receptor modulator (SERM)-like compounds have been shown to use non-ERE pathways, such as tethering of ER-beta to NF-kappaB binding proteins, Sp2, or Ap1 for gene transactivation. These findings open new avenues for drug design that now focuses on developing a new generation of estrogen-based PCa therapies with maximal proapoptotic action but few or no side effects.

OECD validation of the Hershberger assay in Japan: Phase 3. Blind study using coded chemicals

The Organization for Economic Co-operation and Development (OECD) has initiated the development of new guidelines for the screening and testing of potential endocrine disrupters. The Hershberger assay is one of the assays selected for validation based on the need for in vivo screening to detect androgen agonists or antagonists by measuring the response of five sex accessory organs and tissues of castrated juvenile male rats: the ventral prostate, the seminal vesicles with coagulating glands, the levator ani and bulbocavernosus muscle complex (LABC), Cowper's glands, and the glans penis. The Phase 1 feasibility demonstration stage of the Hershberger validation program has been successfully completed with a single androgen agonist and a single antagonist as reference substances. The Phase 2 validation study was performed, employing a range of additional androgen agonists and antagonists. Recently, the Phase 3 validation study was conducted and performed in several International laboratories. Three Japanese laboratories have contributed to the blind study using coded materials of Phase 3 validation. Four coded test substances in the agonistic version and seven substances in the antagonistic version were orally administered by gavage for 10 consecutive days, respectively. In the antagonist version of the assay, 0.2mg/kg/day of testosterone propionate (TP) was coadministered by subcutaneous injection. All five accessory sex reproductive organs and tissues consistently responded with statistically significant changes in weight within a narrow window in both versions. Therefore, the Japanese studies support the Hershberger assay as a reliable and reproducible screening assay for the detection of androgen agonistic and antagonistic effects.

Updated meta-analysis of clinical trials of Serenoa repens extract in the treatment of symptomatic benign prostatic hyperplasia

OBJECTIVES

To determine, by analysing all available clinical trial data, the clinical efficacy against placebo of an extract from the fruit of the American dwarf palm tree, Serenoa repens (Permixon, Pierre Fabre Médicament, Castres, France), as there is controversy about the use of phytotherapeutic agents in men with lower urinary tract symptoms (LUTS) suggestive of benign prostatic hyperplasia (BPH).

METHODS

All clinical trial data published on Permixon, comprising 14 randomized clinical trials and three open-label trials, involving 4280 patients, were analysed. These trials were of different size (22-1100 patients) and duration (21-720 days). The peak urinary flow rate and nocturia were the two common endpoints. The statistical analysis was based on a random-effects meta-analysis.

RESULTS

Permixon was associated with a mean (sem) reduction in the International Prostate Symptom Score (IPSS) of 4.78 (0.41). The mean placebo effect on peak urinary flow rate was an increase of 1.20 (0.49) mL/s. The estimated effect of Permixon was a further increase of 1.02 (0.50) mL/s (P = 0.042). Placebo was associated with a reduction in the mean number of nocturnal voids of 0.63 (0.14); there was a further reduction attributable to Permixon of 0.38 (0.07) (P < 0.001). There was some heterogeneity among the studies for nocturia; one over 2 years involving 396 patients and showing no difference between placebo and Permixon had a large effect on the results.

CONCLUSIONS

This meta-analysis of all available published trials of Permixon for treating men with BPH showed a significant improvement in peak flow rate and reduction in nocturia above placebo, and a 5-point reduction in the IPSS.

Comparison of the Hershberger assay and androgen receptor binding assay of twelve chemicals

We performed the Hershberger assay of 12 chemicals based on the OECD draft protocol. The chemicals tested by the Hershberger assay were phthalic acid di-n-hexyl ester, phthalic acid di-n-amyl ester, phthalic acid di-n-propyl ester, diethylstilbestrol, 17beta-estradiol, tamoxifen, 5alpha-dihydrotestosterone, dichlorodiphenyldichloroethane, cyproterone acetate, 6alpha-methyl-17alpha-hydroxy-progesterone, atrazine, and spironolactone. Phthalic acid di-n-hexyl ester, phthalic acid di-n-amyl ester, and phthalic acid di-n-propyl ester are phthalates; diethylstilbestrol and 17beta-estradiol are estrogenic chemicals; tamoxifen is partial estrogen receptor antagonist with mainly estrogenic properties; 5alpha-dihydrotestosterone is an androgen derivatives; dichlorodiphenyldichloroethane is a reference androgen antagonistic chemical; cyproterone acetate, 6alpha-methyl-17alpha-hydroxy-progesterone, and spironolactone have an androgenic steroid structure and are known as androgen antagonistic chemicals; and atrazine is a reference endocrine disruptor. We also subjected these chemicals to the receptor binding assay for androgen. A clear androgen agonistic effect was detected in 5alpha-dihydrotestosterone, and an androgen antagonistic effect was observed in five chemicals: cyproterone acetate, spironolactone, 6alpha-methyl-17alpha-hydroxy-progesterone, phthalic acid di-n-amyl ester, and dichlorodiphenyldichloroethane. By contrast, diethylstilbestrol, 17beta-estradiol, tamoxifen, 5alpha-dihydrotestosterone, dichlorodiphenyldichloroethane, cyproterone acetate, 6alpha-methyl-17alpha-hydroxy-progesterone, and spironolactone were positive in the receptor binding assay for androgen. Three estrogenic chemicals, diethylstilbestrol, 17beta-estradiol, and tamoxifen, were negative in the Hershberger assay with receptor binding affinity. On the other hand, the Hershberger assays of three phthalates were performed at the same dosages, and the results showed androgen antagonistic affinity only in the assay of phthalic acid di-n-amyl ester without receptor binding affinity.

Estrogens and anti-estrogens: Key mediators of prostate carcinogenesis and new therapeutic candidates

Despite the historical use of estrogens in the treatment of prostate cancer (PCa) little is known about their direct biological effects on the prostate, their role in carcinogenesis, and what mechanisms mediate their therapeutic effects on PCa. It is now known that estrogens alone, or in synergism with an androgen, are potent inducers of aberrant growth and neoplastic transformation in the prostate. The mechanisms of estrogen carcinogenicity could be mediated via induction of unscheduled cell proliferation or through metabolic activation of estrogens to genotoxic metabolites. Age-related changes and race-/ethnic-based differences in circulating or locally formed estrogens may explain differential PCa risk among different populations. Loss of expression of estrogen receptor (ER)-beta expression during prostate carcinogenesis and prevention of estrogen-mediated oxidative damage could be exploited in future PCa prevention strategies. Re-expression of ER-beta in metastatic PCa cells raises the possibility of using ER-beta-specific ligands in triggering cell death in these malignant cells. A variety of new estrogenic/anti-estrogenic/selective estrogen receptor modulator (SERM)-like compounds, including 2-methoxyestradiol, genistein, resveratrol, licochalcone, Raloxifene, ICI 182,780, and estramustine are being evaluated for their potential in the next generation of PCa therapies. Increasing numbers of patients self-medicate with herbal formulations such as PC-SPES. Some of these compounds are selective ER-beta ligands, while most of them have minimal interaction with ER-alpha. Although many may inhibit testosterone production by blockade of the hypothalamal-pituitary-testis axis, the most effective agents also exhibit direct cytostatic, cytotoxic, or apoptotic action on PCa cells. Some of them are potent in interfering with tubulin polymerization, blocking angiogenesis and cell motility, suppressing DNA synthesis, and inhibiting specific kinase activities. Further discovery of other compounds with potent apoptotic activities but minimal estrogen action should promote development of a new generation of effective PCa preventive or treatment regimens with few or no side-effects due to estrogenicity. Further advancement of our knowledge of the role of estrogens in prostate carcinogenesis through metabolic activation of estrogens and/or ER-mediated pathways will certainly result in better preventive or therapeutic modalities for PCa.

Partial sequencing and tissue distribution of the canine isoforms of steroid 5alpha-reductase type I and type II

BACKGROUND

The dog is regarded to be a valid model to test the effects of 5alpha-reductase inhibitors on prostatic growth. However, limited information is available on the characteristics or even existence of 5alpha-reductase isozymes in this species.

METHODS

Here, we set out to clone the cDNA of the dog isoforms of 5alpha-reductase type I and type II by a degenerate cloning strategy and to assess the tissue distribution of both transcripts and the enzymatic activity of the isozymes.

RESULTS

We identified two clones with homology to the human 5alpha-reductase isoforms type I and type II to be expressed in dog prostate. At the amino-acid level, these partial clones were found to exhibit a homology with their human counterparts of 83% and 88%, respectively. The expression levels of 5alpha-reductase mRNA were screened by RT-PCR in a number of dog tissues. No correlation was found between tissue mRNA expression and enzymatic 5alpha-reductase activities.

CONCLUSIONS

The present study describes the partial cloning of the dog 5alpha-reductase isozymes and their tissue distribution. These results provide additional data for the use of the dog as an animal model to investigate the role of 5alpha-reductase isozymes in steroid metabolism.

Meta-analysis of clinical trials of permixon in the treatment of symptomatic benign prostatic hyperplasia

OBJECTIVES

Permixon is a compound extracted from the fruit of the American dwarf palm tree, Serenoa repens. Controversy regarding the use of phytotherapeutic agents in men with lower urinary tract symptoms suggestive of benign prostatic hyperplasia is significant. We analyzed all available clinical trial data of the Permixon preparation to determine its clinical efficacy compared with placebo.

METHODS

All published clinical trial data on Permixon (11 randomized clinical trials and 2 open label trials), involving 2859 patients, were used. These trials were disparate in size (from 22 to 592 patients) and duration (from 21 to 180 days). Peak urinary flow rate and nocturia were the two common end points. The statistical analysis was based on a random effects meta-analysis.

RESULTS

The average +/- SE placebo effect on the peak urinary flow rate was an increase of 0.51 +/- 0.51 mL/s. The estimated effect of Permixon was a further increase of 2.20 +/- 0.51 mL/s (P <0.001). Placebo was associated with a reduction in the mean number +/- SE of nocturnal urinations of 0.69 +/- 0.15. A further reduction of 0.50 +/- 0.01 episodes of urination (P <0.001) occurred that was attributable to Permixon. Some heterogeneity was found among the studies. Treatment duration did not appear to impact either of these effects.

CONCLUSIONS

This meta-analysis of all available published trials of Permixon in the treatment of men with benign prostatic hyperplasia revealed a significant improvement in peak flow rate and reduction in nocturia greater than with placebo.

Effect of early treatment of prostate cancer with the 5alpha-reductase inhibitor turosteride in Dunning R3327 prostatic carcinoma in rats

BACKGROUND

Turosteride, a selective 5alpha-reductase inhibitor, was reported to be effective in inhibiting the growth of established tumors in the Dunning R3327 rat prostatic carcinoma model. We evaluated the preventive effect of turosteride when administered during the latency period in this prostatic tumor model.

METHODS

Turosteride was given orally, 6 days a week for 10-15 weeks, starting at different times: 1) 5 weeks after tumor implantation, when tumors were not yet palpable, or 2) 1 day after tumor implantation. In each experiment, one group of animals was castrated on the first treatment day.

RESULTS

When treatment started 5 weeks after tumor implantation, neither turosteride (at 50 and 200 mg/kg/day) nor castration reduced tumor incidence (91-100%). Tumor growth was reduced in groups treated with the highest dose of turosteride and in castrated rats. When treatment started 1 day after tumor implantation, castration resulted in a 62% tumor incidence compared to 100% in controls, while turosteride at 200 mg/kg/day was not effective in reducing tumor incidence. However, as in the previous experiment, the compound was highly effective in reducing tumor growth.

CONCLUSIONS

The antitumor activity profile of turosteride seems not to be related to the timing of treatment. Given either 5 weeks or 1 day after tumor implantation, the compound did not reduce tumor take, while it maintained effective tumor growth-inhibiting activity in both cases.

Identification and partial characterization of two steroid 5 alpha-reductase isozymes in the canine prostate

BACKGROUND

The dog has been extensively used as an in vivo model to test the pharmacokinetics and effects on pathological prostatic growth of 5 alpha-reductase inhibitors. However, no information is available on the existence or characteristics of canine 5 alpha-reductase isozymes.

METHODS

The 5 alpha-reduction of testosterone is analyzed in dog prostatic homogenates. Three human-specific inhibitors are tested for their activity against dog 5 alpha-reductase.

RESULTS

Two pH optima of 5 alpha-reductase activity in dog prostatic homogenates are described, comparable to the pH optima of rat and human 5 alpha-reductase isozymes. Kinetic analysis of 5 alpha-reductase enzymatic activity at pH 7.0 revealed isozymes with a low apparent affinity constant (Km = 2.67 nM) and a high apparent affinity constant (Km = 1.23 microM). These apparent affinity constants compare favorably to the human and rat isozymes types II and I, respectively. The human type II inhibitor finasteride selectively inhibited the low Km isozyme, whereas the human type I inhibitor MK386 preferentially inhibited the high Km isozyme. The human type I inhibitor LY306089 was nonspecific for the dog isozymes.

CONCLUSIONS

We postulate that the high and low Km isozymes described here represent the dog type I and type II 5 alpha-reductase isozymes, respectively.

Treatment of androgen excess in females: yesterday, today and tomorrow

Hirsutism, acne and androgenic alopecia represent, in females, some of the manifestations of the clinical spectrum of hyperandrogenism. These pictures represent not only cosmetic damage, but also a source of remarkable psychological distress. Often hirsutism is regarded as presumptive evidence of a lack of femininity. The major diagnostic concern is to exclude an ovarian or adrenal androgen-secreting tumor, a congenital hyperplasia or polycystic ovary disease. Ethnic background should be taken into account together with the progression of the symptoms. Following the etiology, surgery and exogenous glucocorticoids or inhibition of gonadotropin secretion have to be carefully chosen in the management of different kinds of hyperandrogenism. Several pharmacologic agents have recently shown the ability to block the androgen receptors at target organ sites, thus allowing a specific antiandrogenic treatment. In some cases cosmetic measures could be of great value. Obesity accompanied by hyperinsulinemia can represent the main cause of ovary androgen hypersecretion; therefore a reduced body weight and muscle activity represent the basis of any treatment. Some other drugs, such as long-acting analogs of somatostatin, could be considered among possible drugs for the future. The aim of this article is to provide an appraisal of what is presently known about the regulation of hair growth, the various causes of excessive androgen secretion and the current methods to solve, safely, this important feminine clinical problem.

Effect of turosteride, a 5 alpha-reductase inhibitor, on the Dunning R3327 rat prostatic carcinoma

BACKGROUND

Turosteride (FCE 26073) is a new, potent, and selective 5 alpha-reductase inhibitor. We have investigated its effect on tumor growth, organ weight, and serum hormone levels in rats bearing the androgen sensitive Dunning R3327 prostatic carcinoma.

METHODS

Animals with tumor diameters of 0.5-1.5 cm were treated for 9 weeks with turosteride (50 and 200 mg/kg/day, 6 days a week, orally), flutamide (25 mg/kg/day, 6 days a week, orally), and leuprolide (300 micrograms/rat, every 3 weeks, subcutaneously) or they were castrated.

RESULTS

Turosteride was ineffective at the dose of 50 mg/kg/day, whereas at 200 mg/kg/ day it significantly decreased tumor growth by 45%. Flutamide and leuprolide were highly effective in reducing tumor growth (70 and 77%), although their effect was slightly lower than that of castration (85%). A significant reduction of ventral prostate weight occurred in rats treated with turosteride at 50 and 200 mg/kg/day (53% and 60%). In contrast to leuprolide and castration, the inhibitory effect of turosteride on tumor growth and prostate weight was not associated to any decrease in serum testosterone.

CONCLUSIONS

Turosteride has antitumor activity on Dunning prostatic tumor growth and its role in prostatic cancer treatment is worthy of further investigation.

Determination of turosteride, a new inhibitor of 5 alpha-reductase, in human plasma by high-performance liquid chromatography with ultraviolet detection

A sensitive and specific HPLC method for the determination of turosteride in human plasma was developed and validated. Turosteride was extracted from plasma with diethyl ether. Further purifications of the fraction extracted were performed sequentially by solid-phase extraction using a CN cartridge and by liquid-liquid partition between n-hexane and acetonitrile. Finally the acetonitrile solution containing the test compound was evaporated to dryness and the residue dissolved in the mobile phase, then injected onto the HPLC system. The chromatographic separation was performed isocratically by a reversed-phase column filled with ODS using a water-acetonitrile-methanol mixture. The eluate was monitored at 210 nm. No peak interfering with that of turosteride was observed when blank human plasma was assayed. Linearity was obtained in the turosteride concentration range of 5-1000 ng/ml plasma. Six calibration curves in plasma prepared and run on six different days showed correlation coefficients higher than 0.99 and good reproducibility of the slope (C.V. = 4.3%). The intra-day precision, evaluated at three concentrations (in the low, mid and high range of the standard curve) and expressed as C.V., ranged from 0.81 to 13.25%. The inter-day precision evaluated at the same concentrations was better than 10.7%. The inter-day accuracy evaluated in the same samples and expressed as the ratio of found/added amount of turosteride ranged from 97.66 to 98.38%. The limit of quantitation was 5 ng/ml plasma. The HPLC method described was successfully employed for the determination of turosteride in plasma samples obtained during a phase I clinical trial with the test compound.

Comparison of phytotherapy (Permixon) with finasteride in the treatment of benign prostate hyperplasia: a randomized international study of 1,098 patients

BACKGROUND

Controversy regarding the relative efficacy of treatments for the relief of the symptoms of benign prostatic hyperplasia (BPH).

METHODS

This was a 6-month double-blind randomized equivalence study that compared the effects of a plant extract (320 mg Permixon) with those of a 5 alpha-reductase inhibitor (5 mg finasteride) in 1,098 men with moderate BPH using the International Prostate Symptom Score (IPSS) as the primary end-point.

RESULTS

Both Permixon and finasteride decreased the IPSS (-37% and -39%, respectively), improved quality of life (by 38 and 41%), and increased peak urinary flow rate (+25% and +30%, P = 0.035), with no statistical difference in the percent of responders with a 3 ml/sec improvement. Finasteride markedly decreased prostate volume (-18%) and serum PSA levels (-41%); Permixon improved symptoms with little effect on volume (-6%) and no change in PSA levels. Permixon fared better than finasteride in a sexual function questionnaire and gave rise to less complaints of decreased libido and impotence.

CONCLUSIONS

Both treatments relieve the symptoms of BPH in about two-thirds of patients but, unlike finasteride, Permixon has little effect on so-called androgen-dependent parameters. This suggests that other pathways might also be involved in the symptomatology of BPH.

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.