Finasteride for benign prostatic hyperplasia.
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5-alpha Reductase Inhibitors↗
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A prospective randomized trial of FK506 versus cyclosporine after human pulmonary transplantation.
We have conducted a unique prospective randomized study to compare the effect of FK506 and cyclosporine (CsA) as the principal immunosuppressive agents after pulmonary transplantation. Between October 1991 and March 1993, 74 lung transplants (35 single lung transplants [SLT], 39 bilateral lung transplant [BLT]) were performed on 74 recipients who were randomly assigned to receive either FK or CsA. Thirty-eight recipients (19 SLT, 19 BLT) received FK and 36 recipients (16 SLT, 20 BLT) received CsA. Recipients receiving FK or CsA were similar in age, gender, preoperative New York Heart Association functional class, and underlying disease. Acute rejection (ACR) was assessed by clinical, radiographic, and histologic criteria. ACR was treated with methylprednisolone, 1 g i.v./day, for three days or rabbit antithymocyte globulin if steroid-resistant. During the first 30 days after transplant, one patient in the FK group died of cerebral edema, while two recipients treated with CsA died of bacterial pneumonia (1) and cardiac arrest (1) (P = NS). Although one-year survival was similar between the groups, the number of recipients free from ACR in the FK group was significantly higher as compared with the CsA group (P < 0.05). Bacterial and viral pneumonias were the major causes of late graft failure in both groups. The mean number of episodes of ACR/100 patient days was significantly fewer in the FK group (1.2) as compared with the CsA group (2.0) (P < 0.05). While only one recipient (1/36 = 3%) in the group treated with CsA remained free from ACR within 120 days of transplantation, 13% (5/38) of the group treated with FK remained free from ACR during this interval (P < 0.05). The prevalence of bacterial infection in the CsA group was 1.5 episodes/100 patient days and 0.6 episodes/100 patient days in the FK group. The prevalence of cytomegaloviral and fungal infection was similar in both groups. Although the presence of bacterial, fungal, and viral infections was similar in the two groups, ACR occurred less frequently in the FK-treated group as compared with the CsA-treated group in the early postoperative period (< 90 days). Early graft survival at 30 days was similar in the two groups, but intermediate graft survival at 6 months was better in the FK group as compared with the CsA group.
Adult↗
Research on the anti-tumour effect of steroid lactam alkylator (NSC-294859) in comparison with conventional chemotherapeutics in malignant melanoma.
Evidence indicating that hybrid steroid compounds of anti-cancer agents produce reduced toxicity, significantly lower than the cytotoxic components alone, and increased anti-cancer activity has prompted the design and development of such steroids, mostly alkylating esters. We investigated the in-vitro and in-vivo activity of a homo-aza-steroidal alkylating ester (HASE), in comparison with dacarbazine (DTIC), cisplatin (CPDD), carmustine (BCNU) and semustine (MeCCNU), in the treatment of malignant melanoma. Cytotoxicity was assessed in vitro by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay using a panel of six human malignant melanoma cell lines, with or without the presence of rat liver microsome assay. B16 melanoma-bearing mice were used to evaluate in vivo the anti-tumour activity of the tested compounds. In all cases of in-vitro screening, HASE displayed a significantly higher (P<0.0001) cytostatic and cytotoxic effect than DTIC, BCNU and MeCCNU, but produced significantly lower (P<0.0001) activity than CPDD. HASE exhibited a significantly smaller range than CPDD between concentration levels that produced growth arrest and those that induced a cytotoxic effect against melanoma cells in vitro. The anti-tumour activity of HASE in B16 melanoma-bearing mice, as determined by tumour growth rate inhibition (<42%) and percentage survival prolongation (treated versus control, 167%), was significantly superior (P<0.001) to that achieved by DTIC, BCNU and MeCCNU and was equal to that of CPDD. HASE exhibited a toxicity similar to that of DTIC, BCNU and MeCCNU, but significantly lower than that of CPDD. It can be concluded that HASE displays significant in-vitro and in-vivo activity in the treatment of melanoma.
Animals↗
5 alpha-reductase inhibitors: what's new?
PURPOSE OF REVIEW: Medical therapy is now the first-line treatment for most men with symptomatic benign prostatic hyperplasia. This review aims to highlight the recent contributions to our understanding of 5 alpha-reductase inhibitor usage. RECENT FINDINGS: For the last decade, finasteride has been the only available 5 alpha-reductase inhibitor, acting upon the type 2 isoenzyme of 5-alpha reductase. Dutasteride is the first drug that can inhibit both isoenzymes and is soon to be available. Biochemically it achieves greater and more rapid dihydrotestosterone suppression compared with finasteride. Clinically, it appears to be at least as good in terms of improving symptoms and flow rates, and reducing the risk of acute urinary retention or the requirement for benign prostatic hyperplasia-related surgery. However, until these two drugs are formally compared, the true benefits of additional type 1 isoenzyme inhibition are unknown. The recently reported Medical Therapy of Prostatic Symptoms trial has convincingly demonstrated superior outcomes with combination therapy compared with monotherapy, unlike previous trials of shorter duration. The ability of 5 alpha-reductase inhibitors to prevent disease progression was also confirmed. Newer roles for 5 alpha-reductase inhibitors are also being defined. Finasteride has been shown to reduce and control benign prostatic hyperplasia-related haematuria, although its value in controlling perioperative bleeding is less clear. Their role as chemopreventive agents for prostate cancer is also under investigation. SUMMARY: Recent studies have both clarified and extended the roles of 5 alpha-reductase inhibitors in benign prostatic hyperplasia, and these may expand further if chemopreventive abilities are proved. In addition, dual isoenzyme inhibition will soon be available.
5-alpha Reductase Inhibitors↗
Chemoprevention using dutasteride: the REDUCE trial.
PURPOSE OF REVIEW: This article will review the design and rationale of the dutasteride prostate cancer chemoprevention trial known as the REDUCE trial (Reduction by Dutasteride of Prostate Cancer Events) in the context of the recently completed Prostate Cancer Prevention Trial. RECENT FINDINGS: The Prostate Cancer Prevention Trial used the 5alpha-reductase inhibitor finasteride to prevent prostate cancer in a prospective randomized trial. The trial demonstrated a nearly 25% reduction in the prevalence of prostate cancer compared with placebo. Finasteride is a type 2-specific 5alpha-reductase inhibitor, whereas dutasteride is an inhibitor of both type 1 and type 2 5alpha-reductase. Recent evidence suggests that there may be increased expression of the type 1 5alpha-reductase in prostate cancer versus benign prostate tissue making dutasteride an attractive agent to study. SUMMARY: Proof of principle has been demonstrated by the Prostate Cancer Prevention Trial that a chemoprevention strategy using a hormonal agent such as a 5alpha-reductase inhibitor can be effective. The REDUCE trial will use the dual 5alpha-reductase inhibitor dutasteride in a group of men identified at increased risk of developing prostate cancer to determine if this will be an effective chemoprevention strategy.
5-alpha Reductase Inhibitors↗
Chemotherapeutic prevention studies of prostate cancer.
PURPOSE: Despite advances in the detection and management of prostate cancer, this disease remains a major cause of morbidity and mortality in men. Increasing attention has focused on the role of chemoprevention for prostate cancer, ie the administration of agents that inhibit 1 or more steps in the natural history of prostate carcinogenesis. We review prostate cancer chemoprevention studies in Europe. MATERIALS AND METHODS: Published studies were identified in a search of MEDLINE. Information about ongoing studies was provided by author access to protocols. RESULTS: A variety of chemoprevention studies have focused on the role of dietary factors, vitamins and trace elements in prostate cancer. Some of these studies have been prospective, randomized and double-blinded, while others have used retrospective or epidemiological approaches. Large scale randomized studies are also evaluating the role of 5alpha-reductase inhibitors, which inhibit the conversion of testosterone to the more potent androgen dihydrotestosterone. CONCLUSIONS: Robust evidence is lacking for the value of chemopreventive agents in prostate cancer. Current evidence does suggest that vitamin E and selenium may have a role in prostate cancer chemoprevention. Data from 2 studies, 1 examining the type 1 5alpha-reductase selective inhibitor finasteride and the other using the dual 5alpha-reductase inhibitor dutasteride, will determine the benefits of androgen inhibition strategies for prostate cancer chemoprevention.
Anticarcinogenic Agents↗
Effect of the dual 5alpha-reductase inhibitor dutasteride on markers of tumor regression in prostate cancer.
PURPOSE: In the prostate testosterone is converted to dihydrotestosterone (DHT) by the enzymes 5alpha-reductase (5alphaR) types 1 and 2 (5alphaR1 and 5alphaR2). Suppression of DHT formation by 5alphaR inhibition may be beneficial in early treatment or prevention of prostate cancer. Although 5alphaR2 is the dominant enzyme in the prostate, evidence indicates that 5alphaR1 may be up-regulated in some prostate cancers. This suggests that dual inhibition of both isoenzymes may be more effective than suppression of 5alphaR2 alone in prostate cancer treatment or prevention. In this short-term pilot study we examined the effect of the dual 5alphaR inhibitor dutasteride on markers of tumor regression. MATERIALS AND METHODS: A total of 46 men with clinically staged T1 or T2 prostate cancer were randomized to receive 5 mg per day of placebo or dutasteride for 6 to 10 weeks before radical prostatectomy. Resected tissues were analyzed to determine the effect of dutasteride on intraprostatic androgen levels, and indices of apoptosis and microvessel density (MVD) in malignant tissue, as well as degree of atrophy in benign tissue. RESULTS: Treatment with dutasteride caused a 97% decrease in intraprostatic DHT and was associated with a trend toward increased apoptosis. In patients receiving dutasteride for 45 days or more, a significant increase in apoptosis and a trend toward decreased MVD in prostate cancer tissue was observed. Dutasteride treatment was also associated with an 18% decrease in mean benign epithelial cell width compared with placebo (p < 0.0001). CONCLUSIONS: In this pilot study dutasteride treatment resulted in almost complete suppression of intraprostatic DHT, increased apoptosis and a trend toward decreased MVD. These findings suggest that short-term treatment with dutasteride can cause regression in some prostate cancers.
5-alpha Reductase Inhibitors↗
Chemoprevention of prostate cancer in men at high risk: rationale and design of the reduction by dutasteride of prostate cancer events (REDUCE) trial.
PURPOSE: Chemoprevention may significantly impact the natural history of prostate cancer. The most potent intraprostatic androgen, dihydrotestosterone, has a significant role in the pathophysiology of prostate cancer. It represents a biologically plausible target for chemoprevention through the inhibition of 5alpha-reductase isoenzymes. MATERIALS AND METHODS: The Reduction by Dutasteride of Prostate Cancer Events clinical trial is an international, multicenter, double-blind, placebo controlled chemoprevention study designed to determine if dutasteride 0.5 mg daily decreases the risk of biopsy detectable prostate cancer. A total of 8,000 men will be randomized to receive dutasteride or placebo for 4 years. Eligible men must be 50 to 75 years old, have a serum prostate specific antigen of 2.5 to 10 ng/ml (ages 50 to 60 years) or 3.0 to 10 ng/ml (older than 60 years). Men must have a negative 6 to 12 core biopsy within 6 months prior to enrollment. Repeat biopsies will be taken at 2 and 4 years. The rates of prostate cancer for each treatment group will be compared. Genetic and protein biomarkers of prostate cancer, and the effect of dutasteride on benign prostatic hyperplasia and prostatitis symptomatology and histopathology will also be assessed. RESULTS: Results remain to be determined. CONCLUSIONS: The study will examine the effects of the dual 5alpha-reductase inhibitor dutasteride on the natural history of prostate cancer in men at increased risk for this malignancy. It affords a unique opportunity to examine biomarkers and genetic linkage for prostate cancer, and assess a range of prostate health outcome measures.
5-alpha Reductase Inhibitors↗
Dihydrotestosterone and the prostate: the scientific rationale for 5alpha-reductase inhibitors in the treatment of benign prostatic hyperplasia.
PURPOSE: We reviewed the physiological and pathogenic role of dihydrotestosterone (DHT), evidence for the beneficial effects of decreasing DHT through 5alpha-reductase inhibition and the effects of altering the androgen balance with these agents. MATERIALS AND METHODS: A review of the relevant literature was done using published studies identified from the MEDLINE database. RESULTS: The androgens DHT and testosterone have complementary roles in male physiology. Each is mediated through the intracellular androgen receptor. It has been hypothesized that DHT may provide an amplification mechanism for testosterone, which could be a beneficial adaptation in men with low circulating testosterone. The recognition of the central role of DHT in benign prostatic hyperplasia (BPH) has changed the way the disease is viewed and has led to the introduction of 5alpha-reductase inhibitors, which can prevent and retard the progression of BPH by suppressing DHT synthesis. The 5alpha-reductase inhibitors decrease prostate volume. In doing so they improve symptoms and urinary flow, and decrease the risks of acute urinary retention and the need for BPH related surgery. The predominant drug related adverse events with 5alpha-reductase inhibitors are reproductive events, that is typically decreased libido, impotence and ejaculatory dysfunction. These events occur in a minority of men and tend to decrease with a longer treatment duration. CONCLUSIONS: DHT appears to have an obligatory role in the development of BPH. The role of 5alpha-reductase inhibitors in the treatment of BPH has been firmly established with an adverse events profile that is suitable for long-term use.
5-alpha Reductase Inhibitors↗
Eliciting preferences for drug treatment of lower urinary tract symptoms associated with benign prostatic hyperplasia.
PURPOSE: There are 2 main medical preparations available for lower urinary tract symptoms resulting from benign prostatic hyperplasia (BPH). Choosing between an alpha-blocker and a 5alpha-reductase inhibitor requires trade-offs between their attributes or characteristics. We investigated the relative importance of and trade-offs between the attributes of the 5alpha-reductase inhibitor dutasteride and alpha-blockers in community dwelling men using a validated technique. MATERIALS AND METHODS: A discrete choice experiment was administered to 211 men older than 40 years who were randomly selected from the general United Kingdom population. Attributes investigated in the discrete choice experiment were time to symptom improvement, sexual and nonsexual side effects, the risks of acute urinary retention (AUR) and surgery, cost and prostate size decrease. Using regression analysis the relative importance of these attributes, the trade-offs that men are willing to make between these attributes and the willingness to pay for each attribute were estimated. RESULTS: All attributes were important to respondents. The most important attribute was side effects. The least preferred side effects was impotence, followed by decreased libido and dizziness. Respondents were willing to wait 13, 2 and 8 months longer for symptom improvement in exchange for decreased prostate size, and the risks of AUR and surgery, respectively. Men reporting moderate symptoms were less concerned about sexual side effects, time to symptom improvement and the risk of AUR compared with men reporting mild symptoms. CONCLUSIONS: Given the attribute levels of BPH medical treatment, overall community dwelling men preferred the 5alpha-reductase inhibitor over alpha-blockers. In the interests of shared decision making it is important to consider the importance of eliciting the preferences of patients with BPH.
Adrenergic alpha-Antagonists↗
GABA receptors on the cell-body membrane of an identified insect motor neuron.
The pharmacology of a gamma-aminobutyric acid (GABA) receptor on the cell body of an identified motor neuron of the cockroach (Periplaneta americana) was investigated by current-clamp and voltage-clamp methods. Iontophoretic application of GABA increased membrane conductance to chloride ions, and prolonged application resulted in desensitization. Hill coefficients, determined from dose-response data, indicated that binding of at least two GABA molecules was required to activate the chloride channel. Differences between vertebrate GABAA receptors and insect neuronal GABA receptors were detected. For the GABA receptor of motor neuron Df, the following rank order of potency was observed: isoguvacine greater than muscimol greater than or equal to GABA greater than 3-aminopropanesulphonic acid. The GABAB receptor agonist baclofen was inactive. Of the potent vertebrate GABA receptor antagonists (bicuculline, pitrazepin, RU5135 and picrotoxin), only picrotoxin (10(-7) M) produced a potent, reversible block of the response to GABA of motor neuron Df. Both picrotoxinin and picrotin also blocked GABA-induced currents. Bicuculline hydrochloride (10(-4) M) and bicuculline methiodide (10(-4) M) were both ineffective when applied at resting membrane potential (-65 mV), although at hyperpolarized levels partial block of GABA-induced current was sometimes observed. Pitrazepin (10(-4) M) caused a partial, voltage-independent block of GABA-induced current. The steroid derivative RU5135 was inactive at 10(-5) M. In contrast to the potent competitive blockade of vertebrate GABAA receptors by bicuculline, pitrazepin and RU5135, none of the weak antagonism caused by these drugs on the insect GABA receptor was competitive. Flunitrazepam (10(-6) M) potentiated GABA responses, providing evidence for a benzodiazepine site on an insect GABA-receptor-chloride-channel complex.
Androstanes↗
Structural studies of thiophilic N-chloroazasteroids.
N-Chloroazasteroids form covalent S-N bonds with thiol groups and so are of interest as chemoselective irreversible binding agents for the active sites of steroid receptors and enzymes. The solid-state structures of N-chloro-3-methoxy-17-aza-D-homo-1,3,5(10)-estratrien-16-one (1), N-chloro-3-methoxy-17-aza-D-homo-1,3,5(10)-estratrien-17a-on e (2) and N-chloro-3-methoxy-16-aza-1,3,5(10)-estratrien-17-one (3) were determined to obtain information about the spatial arrangement of the N-Cl groups. Crystal data: (1) C19H24ClNO2, Mr = 333.84, orthorhombic, P2l2l2l, a = 8.0190 (3), b = 12.7175 (5), c = 16.5047 (9) A, V = 1683.2 (1) A3, Z = 4, Dx = 1.317 g cm-3, lambda(Cu K alpha) = 1.54178 A, mu = 20.9 cm-1, F(000) = 712, T = 295 K, R = 0.045 for 1786 observed reflections; (2) C19H24ClNO2, Mr = 333.84, orthorhombic, P2l2l2l, a = 10.9853 (7), b = 11.8216 (5), c = 12.9851 (9) A, V = 1686.3 (2) A3, Z = 4, Dx = 1.315 g cm-3, lambda(Cu K alpha) = 1.54178 A, mu = 20.9 cm-1, F(000) = 712, T = 295 K, R = 0.035 for 1891 observed reflections; (3) C18H22ClNO2, Mr = 319.81, monoclinic, P2l, a = 13.246 (2), b = 7.972 (2), c = 7.696 (3) A, beta = 90.24 (2) degrees, V = 812.7 (4) A3, Z = 2, Dx = 1.307 g cm-3, lambda(Cu K alpha) = 1.54178 A, mu = 21.4 cm-1, F(000) = 340, T = 295 K, R = 0.045 for 1636 observed reflections.(ABSTRACT TRUNCATED AT 250 WORDS)
Azasteroids↗
Effects of homo-aza-steroids on acute non-lymphocytic leukaemia cell proliferation in vitro.
Homo-aza-steroids (modified steroid molecules) in their esterified forms have been used extensively as carrier molecules of alkylating agents against several neoplastic malignancies in vivo and in vitro. We studied the effects of two homo-aza-steroid carrier molecules alone, namely 3 beta-hydroxy-13 alpha-amino-13,17-seco-5 alpha-androstan-17-oic-13, 17-lactam (compound 1) and 13 alpha-amino-13,17-seco-1,3,5-estratrien-17-oic- 13,17-lactam (compound 2), on human acute non-lymphocytic leukaemia cell proliferation in vitro. We used peripheral blood samples from 27 untreated ANLL patients (eight M1, four M2, two M3, six M4, three M5a, two M5b and two M6, according to FAB criteria). Proliferative activity was estimated by using thymidine uptake and the percentage of cells in metaphase in 24, 48 and 72 h of culture. Exposure of human leukaemic blasts with either of the two compounds resulted in enhanced cell proliferation in M1, M2, M4, M6 and M5a (only by compound 2) cases, whereas there was no significant effect in the M3 and M5b cases. Our results indicate that the two compounds tested exhibit stimulatory effect on cell proliferation, particularly in blast cells possessing a relatively smaller degree of differentiation (M1 and M6 cases exhibiting CD34 and CD7). Further research is needed to study the cell growth effect and the therapeutic potential of these steroid molecules in human blood malignancies in vitro and in vivo.
Azasteroids↗
Preclinical studies on NSC290205 aza-steroid alkylator activity in combination with adriamycin against lymphoid leukaemia.
Summary NSC290205 (A) is an hybrid synthetic antineoplastic ester that is a combination of a d-lactam derivative of androsterone and an alkylating derivative of N,N-bis(2-chloroethyl)aniline. We tested NSC290205 for synergistic antileukaemic activity with adriamycin (ADR), (i) in vitro against the human lymphoid leukaemia cell lines: CCRF-CEM, MOLT-4, and RPMI-8226, (ii) in vivo against P388 lymphocytic and L1210 lymphoid murine leukaemias (at incipient and advanced phase). Our results indicated significant cytostatic and cytotoxic synergy of NSC290205 and ADR in vitro. We further examined these results in vivo by replacing cyclophosphamide in the standard CHOP (cyclophosphamide, hydroxydaunomycin, Oncovin, prednisone) regimen with NSC290205 (AHOP) and comparing the efficiency of these two regimens in vivo. Although treatment of P388 and L1210 with cyclophosphamide or NSC290205 alone yielded equivalent results, AHOP produced a clear benefit for survival compared with CHOP against advanced leukaemias, confirming the in vitro observations [higher percentage increase in median lifespan of treated animals over the untreated (control): 188% and 239% in L1210, 308% and 353% in P388, P < 0.01, for CHOP and AHOP respectively]. AHOP also proved to be more genotoxic and cytostatic than CHOP, inducing higher sister chromatid exchange levels and cell division delays on P388 cells in vivo. NSC290205 showed superior antineoplastic potential against lymphoid leukaemia and significant synergy with ADR, producing an excellent therapeutic outcome.
Animals↗
Prolonged treatment with finasteride (a 5 alpha-reductase inhibitor) does not affect bone density and metabolism.
OBJECTIVE: Since it is not clear whether testosterone or dihydrotestosterone is the active hormone in bone metabolism, we wished to assess the effect of finasteride, a 5 alpha-reductase inhibitor, or vertebral bone mineral density and parameters of bone and mineral metabolism. DESIGN: Patients were treated in a randomized, double-blind controlled study with either placebo, 1 or 5 mg/day finasteride. PATIENTS: Twenty-three men with benign prostatic hyperplasia (BPH) were included in this study; eight received placebo, seven were allocated to treatment with 1 mg/day, and eight to 5 mg/day finasteride for 12 months. MEASUREMENTS: Vertebral bone mineral density was measured at the lumbar spine by dual energy X-ray bone densitometry. Serum calcium, phosphorus, parathyroid hormone, osteocalcin and vitamin D metabolites were measured regularly. Urinary calcium and creatinine excretion were monitored as well. RESULTS: Finasteride caused a significant decrease in serum dihydrotestosterone after 6 and 12 months, but no effect on serum testosterone. Vertebral bone mineral density remained unaltered. None of the other parameters monitored were affected except for a small unexplained increase in 1.25-dihydroxyvitamin D in the group receiving 5 mg finasteride/day. CONCLUSIONS: Testosterone is probably the active hormone in bone metabolism. However, oestradiol, the product of testosterone aromatization (which remains unaltered under finasteride) may yet be another possible responsible steroid in the maintenance of bone density. We can also not rule out that the small amount of dihydrotestosterone remaining under finasteride administration is sufficient for maintaining normal bone metabolism.
5-alpha Reductase Inhibitors↗
Inhibition of 5 alpha-reductase does not simulate the effects of androgen deprivation on porphyrin metabolism by harderian glands from the male Syrian hamster.
As 5 alpha-reductase is involved in the metabolism of indolamines in the Harderian glands of Syrian hamsters, we have compared the effects of androgen deprivation and the administration of the potent 5 alpha-reductase inhibitor N,N-diethyl-4-methoxy-3-oxo-4-aza-5-androstene-17-carboxamida on Harderian porphyrin metabolism. Ten days after castration, porphyrin levels had increased to 40 times the values of intact hamsters. However, the inhibition of 5 alpha-reductase, which resulted in a significant decrease in the weight of accessory sex glands, did not modify porphyrin concentrations within the Harderian glands. It is concluded that, contrary to the situation for indolamine metabolism, testosterone per se is the main androgen involved in the sexual differences observed in Harderian porphyrin metabolism.
Androgens↗
Anxiolytic effect of progesterone is mediated by the neurosteroid allopregnanolone at brain GABAA receptors.
Previous studies from this laboratory have shown that progesterone (PROG) treatment in ovariectomized rats produces an anti-anxiety response similar to that observed after the administration of prototypical anxiolytic benzodiazepine (BDZ) compounds. The PROG-induced anxiolytic response was highly correlated with an increased level of 3 alpha-hydroxy-5 alpha-pregnan-20-one (allopregnanolone) in the blood and brain, and was also associated with a facilitation of GABA-stimulated chloride ion (Cl-) influx in cortical synaptoneurosomes. This correlative evidence suggested that the anxiolytic effect of PROG was a result of its in vivo reduction to the neuroactive steroid, allopregnanolone. In this report, a series of studies was conducted to determine the mechanism(s) by which PROG alters behavior in animal models of anxiety. In the first experiment, ovariectomized rats were injected with PROG (1 mg/0.2 ml, SC) 4 h prior to a test in the elevated plus-maze. Some animals also received an injection of picrotoxin (0.75 mg/kg, IP), a GABAA receptor-gated Cl- channel antagonist, whereas other animals were pretreated with RU 38486 (5 mg/0.2 ml, SC), a progestin receptor antagonist. PROG elicited anxiolytic behavior in the plus-maze, an effect that was blocked by picrotoxin administration. Pretreatment with RU 38486 was not effective in altering PROG-induced anxiolytic behavior in the plus-maze. In a second experiment, the effect of PROG on behavior in the plus-maze was determined in the presence of N,N-diethyl-4-methyl-3-oxo-4-aza-5 alpha-androstane-17 beta-carboxamide (4-MA; 10 mg/0.2 ml, SC), a 5 alpha-reductase inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)
Analysis of Variance↗
Structural requirements for maximal inhibitory allosteric effect of estrogens and estrogen analogues on glutamate dehydrogenase.
The inhibition of glutamate dehydrogenase by estrogens, estrogen analogues or polyphenylethylene derivatives (about one hundred molecules, most of them having estrogenic or antiestrogenic activities) was measured. The efficiency of these compounds in inducing allosteric inhibition of the enzyme was compared and correlated to their chemical structure: an aromatic ring A, a free phenolic group in the region of carbon 3 of the steroid nucleus and a lipophilic substitution in the region of C-12, C-13 or C-17 were found to be the main structural features required for maximal efficiency on glutamate dehydrogenase. A tentative model for the relative orientation of the main inhibitor families is proposed. It accounts for most of the kinetic results and can be used as a tool for the selection of affinity labels directed towards the estrogen binding site of glutamate dehydrogenase.
Allosteric Site↗