Common challenges and problems in clinical trials of boron neutron capture therapy of brain tumors.

Clinical trials for binary therapies, like boron neutron capture therapy (BNCT), pose a number of unique problems and challenges in design, performance, and interpretation of results. In neutron beam development, different groups use different optimization parameters, resulting in beams being considerably different from each other. The design, development, testing, execution of patient pharmacokinetics and the evaluation of results from these studies differ widely. Finally, the clinical trials involving patient treatments vary in many aspects such as their dose escalation strategies, treatment planning methodologies, and the reporting of data. The implications of these differences in the data accrued from these trials are discussed. The BNCT community needs to standardize each aspect of the design, implementation, and reporting of clinical trials so that the data can be used meaningfully.

An investigation on the use of removal-diffusion theory for BNCT treatment planning: a method for determining proper removal-diffusion parameters.

This paper outlines a method for determining proper removal-diffusion parameters to be used in removal-diffusion theory calculations for the purpose of BNCT treatment planning. Additionally, this paper demonstrates that, given the proper choice of removal-diffusion parameters, removal-diffusion theory may provide an accurate calculation technique for determining absorbed dose distributions for the purpose of BNCT treatment planning. For a four-group, one-dimensional calculation in water, this method was used to determine values for the neutron scattering cross sections, neutron removal cross sections, neutron diffusion coefficients, and extrapolation distances. These values were then used in a one-dimensional DIF3D calculation. The results of the DIF3D calculation showed a maximum deviation of 2.5% from a MCNP calculation performed for the same geometry.

A comparison of neutron beams for BNCT based on in-phantom neutron field assessment parameters.

In this paper our in-phantom neutron field assessment parameters, T and DTumor, were used to evaluate several neutron sources for use in BNCT. Specifically, neutron fields from The Ohio State University (OSU) Accelerator-Based Neutron Source (ABNS) design, two alternative ABNS designs from the literature (the Al/AIF3-Al2O3 ABNS and the 7LiF-AI2O3 ABNS), a fission-convertor plate concept based on the 500-kW OSU Research Reactor (OSURR), and the Brookhaven Medical Research Reactor (BMRR) facility were evaluated. In order to facilitate a comparison of the various neutron fields, values of T and DTumor were calculated in a 14 cm x 14 cm x 14 cm lucite cube phantom located in the treatment port of each neutron source. All of the other relevant factors, such as phantom materials, kerma factors, and treatment parameters, were kept the same. The treatment times for the OSURR, the 7LiF-Al2O3 ABNS operating at a beam current of 10 mA, and the BMRR were calculated to be comparable and acceptable, with a treatment time per fraction of approximately 25 min for a four fraction treatment scheme. The treatment time per fraction for the OSU ABNS and the Al/AlF3-Al2O3 ABNS can be reduced to below 30 min per fraction for four fractions, if the proton beam current is made greater than approximately 20 mA. DTumor was calculated along the bean centerline for tumor depths in the phantom ranging from 0 to 14 cm. For tumor depths ranging from 0 to approximately 1.5 cm, the value of DTumor for the OSURR is largest, while for tumor depths ranging from 1.5 to approximately 14 cm, the value of DTumor for the OSU-ABNS is the largest.

Boron neutron capture therapy of brain tumors: biodistribution, pharmacokinetics, and radiation dosimetry sodium borocaptate in patients with gliomas.

OBJECTIVE: The purpose of this study was to obtain tumor and normal brain tissue biodistribution data and pharmacokinetic profiles for sodium borocaptate (Na2B12H11SH) (BSH), a drug that has been used clinically in Europe and Japan for boron neutron capture therapy of brain tumors. The study was performed with a group of 25 patients who had preoperative diagnoses of either glioblastoma multiforme (GBM) or anaplastic astrocytoma (AA) and were candidates for debulking surgery. Nineteen of these patients were subsequently shown to have histopathologically confirmed diagnoses of GBM or AA, and they constituted the study population. METHODS: BSH (non-10B-enriched) was infused intravenously, in a 1-hour period, at doses of 15, 25, and 50 mg boron/kg body weight (corresponding to 26.5, 44.1, and 88.2 mg BSH/kg body weight, respectively) to groups of 3, 3, and 13 patients, respectively. Multiple samples of tumor tissue, brain tissue around the tumors, and normal brain tissue were obtained at either 3 to 7 or 13 to 15 hours after infusion. Blood samples for pharmacokinetic studies were obtained at times up to 120 hours after termination of the infusion. Sixteen of the patients underwent surgery at the Beijing Neurosurgical Institute and three at The Ohio State University, where all tissue samples were subsequently analyzed for boron content by direct current plasma-atomic emission spectroscopy. RESULTS: Blood boron values peaked at the end of the infusion and then decreased triexponentially during the 120-hour sampling period. At 6 hours after termination of the infusion, these values had decreased to 20.8, 29.1, and 62.6 microg/ml for boron doses of 15, 25, and 50 mg/kg body weight, respectively. For a boron dose of 50 mg/kg body weight, the maximum (mean +/- standard deviation) solid tumor boron values at 3 to 7 hours after infusion were 17.1+/-5.8 and 17.3+/-10.1 microg/g for GBMs and AAs, respectively, and the mean tumor value averaged across all samples was 11.9 microg/g for both GBMs and AAs. In contrast, the mean normal brain tissue values, averaged across all samples, were 4.6+/-5.1 and 5.5+/-3.9 microg/g and the tumor/normal brain tissue ratios were3.8 and 3.2 for patients with GBMs and AAs, respectively. The large standard deviations indicated significant heterogeneity in uptake in both tumor and normal brain tissue. Regions histopathologically classified either as a mixture of tumor and normal brain tissue or as infiltrating tumor exhibited slightly lower boron concentrations than those designated as solid tumor. After a dose of 50 mg/kg body weight, boron concentrations in blood decreased from 104 microg/ml at 2 hours to 63 microg/ml at 6 hours and concentrations in skin and muscle were 43.1 and 39.2 microg/g, respectively, during the 3- to 7-hour sampling period. CONCLUSION: When tumor, blood, and normal tissue boron concentrations were taken into account, the most favorable tumor uptake data were obtained with a boron dose of 25 mg/kg body weight, 3 to 7 hours after termination of the infusion. Although blood boron levels were high, normal brain tissue boron levels were almost always lower than tumor levels. However, tumor boron concentrations were less than those necessary for boron neutron capture therapy, and there was significant intratumoral and interpatient variability in the uptake of BSH, which would make estimation of the radiation dose delivered to the tumor very difficult. It is unlikely that intravenous administration of a single dose of BSH would result in therapeutically useful levels of boron. However, combining BSH with boronophenylalanine, the other compound that has been used clinically, and optimizing their delivery could increase tumor boron uptake and potentially improve the efficacy of boron neutron capture therapy.

Comparative rates of androgen production and metabolism in Caucasian and Chinese subjects.

Clinically apparent prostate cancer occurs more commonly among Caucasians living in Western countries than in Chinese in the Far East. Prior studies demonstrated diminished facial and body hair and lower levels of plasma 3 alpha-androstanediol glucuronide and androsterone glucuronide in Chinese than in Caucasian men. Based upon these findings, investigators postulated that Chinese men could have diminished 5 alpha-reductase activity with a resultant decrease in prostate tissue dihydrotestosterone levels and clinically apparent prostate cancer. An alternative hypothesis suggests that decreased 3 alpha-androstanediol glucuronide and androsterone glucuronide levels might reflect reduced production of androgenic ketosteroid precursors as a result of genetic or environmental factors. The present study examined 5 alpha-reductase activity, androgenic ketosteroid precursors, and the influence of genetic and environmental/dietary factors in groups of Chinese and Caucasian men. We found no significant differences in the ratios of 5 beta-:5 alpha-reduced urinary steroids (a marker of 5 alpha-reductase activity) between Chinese subjects living in Beijing, China, and Caucasians living in Pennsylvania. To enhance the sensitivity of detection, we used an isotopic kinetic method to directly measure 5 alpha-reductase activity and found no difference in testosterone to dihydrotestosterone conversion ratios between groups. Then, addressing the alternative hypothesis, we found that the Caucasian subjects excreted significantly higher levels of individual and total androgenic ketosteroids than did their Chinese counterparts. To distinguish genetic from environmental/dietary factors as a cause of these differences, we compared Chinese men living in Pennsylvania and a similar group living in Beijing, China. We detected a reduction in testosterone production rates and total plasma testosterone and sex hormone-binding levels, but not in testosterone MCRs in Beijing Chinese as a opposed to those living in Pennsylvania. Comparing Pennsylvania Chinese with their Caucasian counterparts, we detected no significant differences in total testosterone, free and weakly bound testosterone, sex hormone-binding globulin levels, and testosterone production rates. Taken together, these studies suggest that environmental/dietary, but not genetic, factors influence androgen production and explain the differences between Caucasian and Chinese men.

Practical considerations for TLD-400/700-based gamma ray dosimetry for BNCT applications in a high thermal neutron fluence.

Operating experience with thermoluminescent dosimeters used in a boron neutron capture therapy research project is reported. In particular, certain facets of the use of thermoluminescent dosimeters for gamma ray dose measurements in the presence of a high thermal neutron fluence are discussed, including a comparison of TLD-400 and TLD-700 for gamma ray dosimetry, annealing procedures, and the effects of neutrons (56Mn activation) on TLD-400. The TLD-400 were observed to have a thermal neutron sensitivity (due to 56Mn beta decay) of 1.5 x 10(-13) Gy per n cm-2. An algorithm was developed to correct for the 56Mn beta decay thermal neutron-induced effects on TLD-400 by using a two-stage thermoluminescent readout for the thermoluminescent dosimeter chips.

Effect of the antiglucocorticoid RU486 on adrenal steroidogenic enzyme activity and steroidogenesis.

RU486, a synthetic steroid receptor antagonist, has strong antiprogesterone and antiglucocorticoid properties. Chronic RU486 administration in two patients with ectopic secretion of adrenocorticotropin (ACTH) has been associated with decreasing plasma cortisol concentrations. One explanation of this finding is that RU486 may directly inhibit adrenal steroidogenesis. To test this hypothesis, we measured the effect of RU486 on specific steroidogenic enzymatic steps using an in vivo rat and an in vitro monkey model. Hypophysectomized-castrated-ACTH-replaced Sprague-Dawley rats were given RU486 i.p. at daily doses of 0, 0.0005, 0.005, 0.05, 0.5 and 5 mg/kg body weight per day for 7 days. The animals were sacrificed, and blood and adrenal glands collected. Adrenal cortical mitochondria and microsomes were purified from the rats and from two untreated Cynomolgus macaque monkeys. Specific steroidogenic enzyme activities were measured in the rat by the incorporation of 14C-labeled steroid substrates into products. A similar protocol was used to assay the steroidogenesis in the monkey adrenal fractions in the presence and absence of added RU486. Although rat adrenal weights decreased significantly at the highest RU486 dose, plasma levels of corticosterone were similar in control and treated rats. Rat adrenal 3 beta-hydroxysteroid dehydrogenase/isomerase (3-HSD), 21-hydroxylase (21-OH) and 11-hydroxylase (11-OH) activities decreased with increasing RU486 doses, with 21-OH and 11-OH being most severely affected. Monkey adrenal 3-HSD, 21-OH, 11-OH, 17-hydroxylase and 17,20-desmolase similarly decreased in the presence of increasing in vitro concentrations of RU486.(ABSTRACT TRUNCATED AT 250 WORDS)

Oestrogen modulation with parturition in the human placenta.

An initial group of term (36-41 6/7 weeks), preterm (less than 36 weeks), and post-term (42 or more weeks) placentae were collected from women at delivery to determine the placental levels of important steroids and steroidogenic enzymes involved in the oestrogen synthesis pathway as a function of gestational age. A second group of placentae were obtained from women delivering at term before and after the onset of labour. Placentae were evaluated individually for cytosolic steroid hormone levels and microsomal steroidogenic enzyme activities. Oestradiol (E2), oestrone (E1), progesterone (P), and delta-4-androstenedione (A) were measured by radioimmunoassay in placental cytosols. Aromatase (AR), sulphatase (S), and 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta HSD) activities were assayed in placental microsomes. Cytosolic concentrations of E1, E2, P, and A did not differ with respect to gestational age. Correspondingly, the microsomal enzyme activities of 3 beta HSD, S, and AR did not vary as a function of gestational age. However, when patients at term who were in labour prior to delivery were compared to those who were not, the placental cytosolic level of E1 was found to be threefold higher in the non-labouring group (4572 versus 1427 pg/mg cytosolic protein, P < 0.025). Additionally, microsomal aromatase activity was also significantly higher in the non-labouring patients (46 versus 19 pM/min/mg protein, P < 0.025), while the E2 to P ratio in the labouring patients was twice that of the non-labouring group, a difference which was significant at the P < 0.025 level (Wilcoxon rank sum test). These data suggest that at term, prior to labour, the placental production of E1 by AR is high, and that AR activity and E1 levels fall significantly after the onset of labour. Also, the placental cytosolic concentration of the more active oestrogen, E2, demonstrates stable to rising levels with a significant increase in E2/P after the onset of labour. We theorize that in the term pregnancy prior to labour, E1 may represent a large but relatively inactive intracellular oestrogen pool which is maintained by high AR activity, and may function to protect the pregnant local uterine environment from the more oxytocic effects of E2.

Enhanced follicle regulatory protein levels accompany reinitiation of ovulatory function after parturition.

OBJECTIVES: We examined the changes in follicle regulatory protein, estrone-3-glucuronide, pregnanediol-3-glucuronide, and luteinizing hormone levels in first-morning urine samples from postpartum, fully breast-feeding women to characterize the reemergence of these urinary hormones after pregnancy ovarian quiescence and early postpartum period and to determine whether follicle regulatory protein could be used prospectively to predict the return of fertility. STUDY DESIGN: Twenty-five hundred urine samples collected from six postpartum women were evaluated. Daily urine samples collected from normally cycling women were used to establish normal urinary hormone and hormone metabolite cyclicity. Luteinizing hormone, estrone-3-glucuronide, and pregnanediol-3-glucuronide levels were measured by radioimmunoassay. Follicle regulatory protein level was assayed with a double-antibody enzyme-linked immunosorbent assay. RESULTS: Although follicle regulatory protein levels were found to be very low or undetectable in early postpartum urine, they began to rise with episodes of estrone-3-glucuronide and pregnanediol-3-glucuronide secretion. A chi 2 analysis suggests that increasing urinary follicle regulatory protein levels are most closely associated with the luteal phase of the first menstrual cycles in postpartum women. CONCLUSIONS: These results suggest that follicle regulatory protein is of little value in predicting either the onset of renewed ovarian activity or the fertile period.

Acute prolactin and oxytocin responses and milk yield to infant suckling and artificial methods of expression in lactating women.

Breast-feeding is today the major form of infant nutrition in the immediate postpartum period. Despite this, recent trends in modern life-styles have raised obstacles to successful lactation. These include infant illness and maternal responsibilities outside the home, both requiring separation from the mother. While the hormonal dynamics of infant suckling are understood, little is known about the effects of artificial methods of milk expression. A variety of breast pumps exist in the current US market which vary considerably in price and effectiveness. To understand better the ability of these pumps to assist women in the maintenance of lactation, the current study was undertaken to evaluate their effects on milk yield and prolactin and oxytocin release when compared to natural infant suckling. Twenty-three women who were exclusively breast-feeding their infants were randomly assigned to serially use several pumping methods, as well as infant suckling, with blood being taken at 10-minute intervals to determine the hormonal responses. The results reveal variability in the prolactin responses to the artificial pumping methods, with the greatest responses found with an electric pulsatile pump; these responses compare favorably with those of natural infant suckling. Other methods were less successful in causing prolactin elevations. No differences were seen among the methods in the oxytocin response. The results of this study demonstrate striking differences in the ability of breast-pumping methods to produce an acute and sustained prolactin rise in breast-feeding mothers. The large discrepancies found suggest the need for further studies in to enable women and health care providers to choose the most appropriate method for milk expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of vehicle supplementation on total estradiol absorption from a transdermal estradiol delivery system.

OBJECTIVE: To evaluate the effects of vehicle supplementation on serum estradiol (E2) delivery pharmacokinetics from the Ciba-Geigy (Summit, NJ) 0.1-mg Estraderm Patch. DESIGN: Postmenopausal women were randomized to a 28-day crossover treatment protocol separated by a 14-day wash out period. SETTING: Normal human volunteers were studied in an academic research environment. PATIENTS, PARTICIPANTS: The subject pool included eight healthy postmenopausal women between 32 and 60 years of age. INTERVENTIONS: In treatment A, a 0.1-mg Estraderm Patch was worn for 7 days; in treatment B, and identical patch was worn into which 0.6 mL of ethanol was injected on day 3 of use. MAIN OUTCOME MEASURES: Serum E2 levels were measured in both groups. RESULTS: Although E2 absorption showed characteristic interpatient variability, addition of ethanol significantly extended the mean time for serum E2 levels to return to baseline, without increasing peak absorption. The mean extension was 50 hours. CONCLUSION: The addition of ethanol to the Estraderm Patch increased the duration of elevated serum E2 levels measured in menopausal women, thus potentially increasing the effective life span of the transdermal therapeutic system.

Genetic variation of the glucocorticoid receptor from a steroid-resistant primate.

The neotropical cotton-top marmoset (Saguinus oedipus) is a New World primate known to have markedly increased total and free plasma cortisol concentrations when compared with Old World primates including man. The relative end-organ 'resistance' to glucocorticoids found in various New World primates has been attributed to a glucocorticoid receptor (GR) with diminished affinity for glucocorticoids. It has been demonstrated that the marmoset GR has approximately tenfold lower binding affinity for dexamethasone when compared with the human GR. We have examined the primary structure of the marmoset GR by molecular cloning and sequencing of GR functional domains. A library of cDNA clones was constructed in the phage vector gamma gt10 using poly(A)+ RNA from a marmoset-derived lymphoid cell line, and screened using the human GR cDNA. DNA sequencing determined 76 individual nucleotide substitutions in the coding region of the marmoset GR. Comparison of the marmoset GR nucleotide sequence with the human GR cDNA coding region indicated an overall sequence homology of about 97%. Thirty of the nucleotide substitutions lead to alterations in the predicted amino acid sequence (28 amino acid substitutions) of the marmoset GR. The size of the marmoset GR predicted from the 778 amino acids is approximately 90,000 which is in agreement with previous size estimates of the human and marmoset GRs. Alterations of amino acid sequence in the marmoset GR were greatest towards the amino terminus, including the tau 1 domain putatively involved in transcriptional activation. The DNA-binding domain contained an additional codon (arginine).(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibitory effects of gossypol on adrenal function.

Gossypol, an antifertility agent, has inhibitory actions on many membrane-associated enzymes, suggesting that this agent might have a generalized effect on cell membranes. This hypothesis was examined in the present study using membranes and dispersed cells prepared from human and rat adrenal glands. Four parameters were determined: microviscosity as measured by fluorescence polarization of human adrenal microsomal- and mitochondrial-enriched membranes, adrenal steroidogenic enzymes; and cAMP and cortisol responses to ACTH. It was found that gossypol increased the polarization constants of microsomes and mitochondria in a dose-dependent manner. Of the three adrenal enzymes tested, both 3 beta-hydroxysteroid dehydrogenase delta 5-delta 4 isomerase and 11-hydroxylase were inhibited by gossypol, but not 21-hydroxylase. Using intact human adrenocortical cells, high doses of gossypol also inhibited the ACTH-stimulated cAMP and cortisol levels. The in vivo corticosterone response to ACTH in rats subjected to chronic gossypol treatment was also found to be reduced. These findings suggest that gossypol has multiple effects on adrenal function. Its effects on membrane microviscosity, adrenal steroidogenesis, cAMP and corticosterone responses to ACTH stimulation probably occur through a generalized membrane effect.

A novel testis-stimulating factor in familial male precocious puberty.

BACKGROUND: Familial male precocious puberty is a gonadotropin-independent form of precocious puberty that occurs only in males. The cause of the disorder is unknown. To examine the hypothesis that the plasma of boys with familial male precocious puberty contains a novel stimulator of testicular testosterone production, we developed a bioassay using adult male cynomolgus monkeys. METHODS: We collected plasma from 12 boys with familial male precocious puberty, 7 normal prepubertal boys of similar ages and with similar plasma gonadotropin levels, and 1 boy with hypogonadotropic hypogonadism and infused it into the testicular artery of adult male cynomolgus monkeys that had been pretreated with gonadotropin-releasing-hormone antagonist to inhibit the endogenous secretion of gonadotropins. Testicular venous effluent was collected at 15-minute intervals for 3 or 5 hours for the measurement of testosterone. RESULTS: The mean (+/- SE) peak testosterone response, as compared with base line, was significantly greater in the monkeys infused with plasma from the 12 boys with familial male precocious puberty than in the monkeys infused with plasma from the 7 normal prepubertal boys and the boy with hypogonadotropic hypogonadism (385 +/- 51 vs. 184 +/- 25 percent, P less than 0.005) in the three-hour studies. Plasma from 92 percent of the boys with familial male precocious puberty and 12.5 percent of the normal prepubertal boys stimulated a response greater than 195 percent of base-line values. In the animals studied for five hours after receiving a second dose of antagonist, the mean peak testosterone response, as compared with base line, was significantly greater in the monkeys infused with plasma from three boys with familial male precocious puberty than in the monkeys infused with plasma from three normal prepubertal boys (363 +/- 81 vs. 115 +/- 6 percent, P less than 0.01). The mean area under the testosterone-response curve was significantly larger in the monkeys infused with plasma from the boys with familial male precocious puberty in the five-hour studies (154 +/- 34 vs. -58 +/- 10 percent, P less than 0.005), but not in the three-hour studies. CONCLUSIONS: These findings support the presence of a circulating testis-stimulating factor in the plasma of boys with familial male precocious puberty. The production of such a factor would explain the biologic nature of the disorder.

Calcium metabolism in postpartum lactation: the effect of estrogen status.

Postpartum lactation represents a unique state of increased calcium demand in which women are also hyperprolactinemic and hypoestrogenic. This is associated with increased calcium mobilization from bone and bone loss. To better understand the effect of estrogen (E) status on calcium metabolism during lactation, we studied 10 long-term lactating women at 12 weeks postpartum when they were hypoestrogenic and again at 37.4 +/- 3.4 (+/- SD) weeks during the midfollicular phase of their second ovulatory cycle. Urinary and serum markers of calcium metabolism were measured at these intervals. The results revealed that when E was low, osteocalcin and hydroxyproline were increased with a lower circulating parathyroid hormone (PTH) level, whereas reciprocal changes were noted when E was increased. The findings suggest that E status can modulate PTH's ability to mobilize one's stores of calcium.

Steroidogenic enzyme activities, morphology, and receptor studies of a testicular adrenal rest in a patient with congenital adrenal hyperplasia.

Steroid-secreting tumors of the testis have generally been considered to be of Leydig cell origin. Testicular tumors in patients with congenital adrenal hyperplasia have been thought to be adrenal rests, but no conclusive evidence supporting the hypothesis has been presented. We report a morphological and biochemical analysis of a patient with 21-hydroxylase deficiency who developed bilateral nodular hyperplasia of steroid-secreting tissue within the testis, despite suppression therapy with both exogenous glucocorticoids and testosterone. The tissue was formed of confluent nodules of homogenous cells. Electron microscopy showed the cells to have abundant smooth endoplasmic reticulum, well developed Golgi apparatus, and mitochondria with predominantly tubular cristae, features characteristic of steroid-secreting cells of adrenocortical origin. Crystals of Reinke were not observed. Functional studies in vivo showed a marked response to ACTH infusion, with 17-hydroxyprogesterone rising from 56 to 13,500 ng/mL, cortisol from less than 2 to 19 micrograms/dL, and testosterone from 369 to 629 ng/dL, with an attendant increase in testicular size and pain over 48 h. Receptor studies in vitro revealed no gonadotropin receptors, but abundant angiotensin-II receptors. Enzyme activity analysis in vitro showed undetectable 21-hydroxylase activity and an enzyme profile consistent with adrenocortical cells rather than Leydig cells. Based on these morphological and biochemical findings, we conclude that the nodular steroidogenic tissue that replaced this patient's testes was of adrenal origin. The study documents for the first time the development of adrenocortical tumors from adrenal rest tissue within the testis.

RU-486 inhibits rat gonadal steroidogenesis.

RU-486 is a synthetic steroid analogue that can inhibit adrenal steroid synthesis in the rat and rhesus monkey. We measured the activities of five testicular and two ovarian microsomal steroidogenic enzymes to assess the potential effect of RU-486 on rat gonadal steroidogenesis. Hypophysectomized, gonadotropin-replaced rats received RU-486 or a vehicle solution twice daily for seven days. The animals were sacrificed and their gonads were resected, weighed, and microsomal enzyme activities were measured according to RU-486 treatment. Testicular 17-hydroxylase and aromatase activity decreased in RU-486 treated animals whereas 17,20-desmolase, 3 beta-hydroxysteroid dehydrogenase and 17-ketosteroid reductase activities were unaffected. Ovarian 17-hydroxylase but not 3 beta-hydroxysteroid dehydrogenase activity was decreased in the animals receiving the drug. We conclude that RU-486 inhibits both testicular and ovarian steroidogenesis in the rat.

The inhibition of human adrenal steroidogenic enzyme activities by suramin.

Suramin has recently been used to treat patients with acquired immune deficiency syndrome because of the action of this drug on reverse transcriptase. Patients so treated developed the symptoms and hormonal profiles of adrenal insufficiency. To evaluate the mechanism of action of suramin on adrenalcortical function, adrenal mitochondrial and microsomal preparations from five subjects were assayed for steroidogenic enzyme activity in the presence and absence of suramin. Specifically, 3 beta-hydroxysteroid dehydrogenase/isomerase, 17 alpha-hydroxylase, 21-hydroxylase, 11 beta-hydroxylase, and 17,20-desmolase activities were measured in the presence of 0-5000 mumol/L suramin concentrations. In all assays, enzyme activities decreased in a dose-dependent fashion as suramin concentrations increased. The drug doses (calculated) that caused 50% inhibition of enzyme activity were: 21-hydroxylase activity, 50 mumol/L; 17 alpha-hydroxylase activity, 25 mumol/L; 17,20-desmolase activity, 50 mumol/L; 11 beta-hydroxylase, 2 mumol/L, and 3 beta-hydroxysteroid dehydrogenase/isomerase, 1200 mumol/L. These results suggest that suramin has a concentration-dependent inhibitory effect on the key P-450-regulated enzymatic steps in adrenal glucocorticoid steroidogenesis, which may explain the development of adrenal insufficiency in acquired immune deficiency syndrome patients treated with suramin.