A case of 16-ene-synthetase deficiency in male pseudohermaphroditism due to combined 17 alpha-hydroxylase/17,20-lyase deficiency.

A 17-year-old phenotypic female with primary hypergonadotropic amenorrhea, absence of secondary sexual development, hypertension and 46 XY karyotype is presented. Hormonal analysis revealed very low levels of testosterone, dehydroepiandrosterone, androstenedione, estrogens, cortisol and high levels of ACTH, progesterone, deoxycorticosterone and corticosterone. Enzyme studies of the testicular tissue after bilateral gonadectomy showed absence of 17 alpha-hydroxylase and 17,20-lyase activity as well as 16-ene-synthetase activity. This enzyme catalyzes the reaction from pregnenolone to 5,16-androstadien-3 beta-ol, a sex pheromone precursor. The other enzyme systems leading from pregnenolone to testosterone were intact. This is the first report of male pseudohermaphroiditism in which the combination of 17 alpha-hydroxylase, 17,20-lyase and 16-ene-synthetase deficiency is described, indicating that all these activities might be associated with the same protein.

The HMG-CoA reductase inhibitor simvastatin suppresses human testicular testosterone synthesis in vitro by a selective inhibitory effect on 17-ketosteroid-oxidoreductase enzyme activity.

In concentrations probably exceeding those achieved in vivo, the cholesterol lowering compound simvastatin was found to suppress the synthesis of the androgens androstenediol and testosterone in vitro by human testicular homogenates. It was demonstrated that simvastatin in addition to its known inhibitory effect on HMG-CoA reductase activity, also affects the later steps of testicular steroidogenesis by selectively inhibiting the 17-ketosteroid-oxidoreductase catalyzed conversion of dehydroepiandrosterone and androstenedione to androstenediol and testosterone respectively. There was no effect of simvastatin on the Cytochrome P-450-dependent microsomal enzymes. Although in doses conventionally used in the treatment of hypercholesterolemia, simvastatin does not affect testicular steroidogenesis, at higher doses--especially when inadvertently administered during early pregnancy--adverse effects on normal testosterone biosynthesis and thereby fetal development should be considered.

16-Ene-steroids in the human testis.

Incubation of human testicular homogenates with [4-14C]pregnenolone gave substantial amounts of an unknown metabolite within 1 min, reaching plateau values of 17-23% of total radioactivity added within 5 min. Mass spectrometry of the metabolite showed it to be identical to the boar sex pheromone precursor androsta-5, 16-diene-3 beta-ol (ADL). In cell cultures the major source of ADL and its dehydrogenated metabolite androsta-4, 16-diene-3-one (ADN) was the Leydig cell. In rat and monkey testicular homogenates 16-ene-synthetase activity, a prerequisite for the synthesis of ADL and ADN, was completely lacking, limiting the presence of 16-androstenes to boars and men. In contrast to boars, however, in the human testis no 5 alpha-reductase activity was found and consequently no 5 alpha-reduced-16-androstenes, e.g. androstenol (AL, musk like) and androstenone (AN, urine like), known sex pheromones in pigs. As both sex pheromones have been identified in urine, plasma, sweat and saliva of men and (especially hirsute) women we hypothesize that AL and AN are synthesized from ADL via ADN peripherically in tissues rich in 5 alpha-reductase, i.e. skin, axillary sweat glands and probably also the salivary glands. So far, there is some evidence that both sex pheromones may have similar functions in humans as in boars.

Differential metabolism of pregnenolone by testicular homogenates of humans and two species of macaques. Lack of synthesis of the human sex pheromone precursor 5,16-androstadien-3 beta-ol in nonhuman primates.

In previous reports we described the early time sequence in in vitro [4-14C] pregnenolone metabolism in human and rat testicular homogenates and, apart from a difference in the preferred route of the conversion of pregnenolone to testosterone, we demonstrated the presence of delta 16-synthetase activity in human but not in rat testes. In the study of testicular function higher monkeys are increasingly used as a model for human reproduction. The availability of testes from 2 different species of macaques (rhesus and crab eating monkeys) enabled us to compare the in vitro metabolism of pregnenolone in these testes with human testes. The pattern obtained in both monkey species were very similar, but completely different from those found in man. The delta 4 pathway was the preferred route for the conversion of pregnenolone to testosterone in the monkeys tested, the delta 5 pathway in the humans. delta 16-Synthetase activity, a prerequisite for the synthesis of the sex pheromone precursors 5,16-androstadien-3 beta-ol and 4,16-androstadien-3-one, was clearly measurable in the human but not in the monkey testicular homogenates. So far, man and boar are the only species harbouring delta 16-synthetase activity in their testes. These in vitro data indicate that the nonhuman primates studied are not suitable models for the study of human testicular function.

The mechanism of the synthesis of 16-androstenes in human testicular homogenates.

The biochemical pathway leading to the 16-unsaturated C19 steroids--known as sex pheromone (precursors) in pig and man--is still a matter of dispute. In the 16-ene-synthetase process, via which 5,16-androstadien-3 beta-ol (ADL) or 4,16-androstadien-3-one (ADN) are biosynthesized from pregnenolone (P5) or progesterone (P4), a number of 2 or even 3 step conversions have been suggested in porcine tests, including 20 beta-reduction, 21-hydroxylation and 16,17-dehydrogenation. Studying the 16-ene-synthetase reaction in human testicular homogenates, we adduced evidence for the hypothesis that ADL is synthesized from P5 in a single step, not requiring separate intermediates. Our proposal for the 16-ene-synthetase mechanism also explains why, at least in our hands, synthesis of ADL is always accompanied by co-synthesis of its satellite 5-androstene-3 beta,17 alpha-diol (epiA5): both steroids are synthesized as a mere consequence of the fact that the proposed elimination and substitution reactions for the synthesis of ADL and epiA5, respectively, are competitive processes.

Partial purification of a polypeptide extract derived from ovine pineal that suppresses the growth of human melanoma cells in vitro.

A combination of gelfiltration and reverse-phase high performance liquid chromatography with postcolumn antitumour assay has been developed. A melatonin insensitive human melanoma cell strain was used to guide the purification of the antitumour effect of an ovine pineal aqueous extract (MW 1,000 to 10,000) that possessed the ability to decrease the hypophysiotropic activity of rat and mice hypothalami in vitro. This allows a specific identification of a pineal factor (MW 2,000 to 6,000) that inhibits the growth of human melanoma cells at a dose of 0.47 mg/ml medium. It was shown that the activity of this pineal compound differs from structures known to be present in the pineal, such as melatonin, pteridines, and beta-carbolines. There appears to be evidence for a peptidic nature of this pineal antitumour factor.

Partial purification of (a) low molecular weight ovine pineal compound(s) with an inhibiting effect on the growth of human melanoma cells in vitro.

An in vitro human melanoma cell assay was used to work up the partial purification of (a) low molecular weight (MW) substance(s) from aqueous extracts of ovine pineal tissue shown to contain a growth-inhibiting activity. A combination of paper chromatography, ion-exchange and reverse-phase high performance liquid chromatography with post-column antitumor assay has been developed. This allows a specific identification of an ovine pineal factor (MW less than 500) which inhibits the growth of human melanoma cells in vitro. The substance was partially purified to about 1,000 times as compared to the IC100-value of the starting material (retentate 5). The growth inhibition of human melanoma cells in culture was complete at a dose of 0.1 microgram/ml of purified pineal factor(s). It was demonstrated that the activity of this pineal compound differs from some substances known to be present in the pineal, such as melatonin, serotonin, peridines and beta-carbolines. The activity was not destroyed by treatment with proteolytic enzymes.

The sex pheromone precursor androsta-5,16-dien-3 beta-ol is a major early metabolite in in vitro pregnenolone metabolism in human testicular homogenates.

In an earlier report we described the early time sequence of the in vitro metabolism of [4-14C]pregnenolone ([4-14C]P5) to testosterone in homogenates of human and rat testes and demonstrated the appearance of mainly delta 5 (humans)- and delta 4 (rats)-steroids within minutes after starting the incubation. In this study strong evidence is presented for the substantial synthesis from P5 of the sex pheromone precursor androsta-5,16-dien-3 beta-ol (ADL) in human, but not rat, testicular homogenates. The 16-unsaturated C19 steroid ADL appeared after 1 min of incubation, and within 5 min reached values (17-23% of total radioactivity added as [4-14C]P5) comparable to those of the major delta 5-steroids 17 alpha-hydroxypregnenolone and dehydroepiandrosterone. Thus, in humans, as in boars, the sex attractant precursor ADL is a major early testicular metabolite of P5.

Early time sequence in pregnenolone metabolism to testosterone in homogenates of human and rat testis.

The time sequence of the metabolism of [4-14C] pregnenolone to testosterone in homogenates of human and rat testis was studied with special emphasis on the chain of events in the early 15 min of incubation. The incubations were performed at 32 C in the presence of NAD and a NADPH-generating system. The various intermediate steroids were separated by means of HPLC using a silica aliphatic diol column. Correction for procedural losses was performed by dual labeling. The present study confirms earlier reported results which showed that in the rat metabolism of pregnenolone to testosterone proceeds via the delta 4 pathway. However, this discloses for the first time that the conversion of pregnenolone proceeds very fast: progesterone, 17 alpha-hydroxyprogesterone, and 17 alpha-hydroxypregnenolone as the only important delta 5 intermediate, peak and decline again to almost undetectable levels within the first 15 min of incubation. Androstenedione and testosterone start to accumulate from 1 min on under the conditions used. In contrast, in the human testis, homogenates metabolism of pregnenolone to testosterone proceeds comparatively slowly and almost exclusively via the delta 5 intermediates dehydroepiandrosterone and androstenediol. Testosterone makes its appearance only after about 8 min of incubation. The data illustrate the importance of short-term incubations in evaluating the metabolism of steroids.

Presence of oestrogen receptors in human blood mononuclear cells and thymocytes.

We studied oestrogen binding sites in blood mononuclear cells from healthy blood donors, patients with leukaemia or systemic lupus erythematosus, and in thymocytes, using the dextran-coated charcoal assay and Scatchard analysis of binding data. Using 3H-labelled oestradiol as ligand, inaccurate results were obtained which could be related to the low amounts of binding sites. Using 125I-labelled ligand, saturable oestradiol binding sites could be demonstrated in low amount (mean value 2.1 fmol/mg of cytosolic protein) and high affinity (mean Kd value 0.26 nM; mean Ka value 3.85 X 10(9) M-1). The binding could be inhibited by unlabelled oestradiol but not with oestrone, dihydrotestosterone, cortisol and the progestin-receptor ligand Org 2058. We conclude that blood mononuclear cells and thymocytes contain true oestrogen receptors. This conclusion supports current hypotheses on the involvement of such receptors in oestrogen-mediated modulation of the immune system.