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Diese Arbeit demonstriert die kombinierte Anwendung unterschiedlicher bioinformatischer Verfahren auf die Familie der 17beta-Hydroxysteroid-Dehydrogenasen. Diese Protein-Familie ist an der Aktivierung und Inaktivierung von Steroid-Hormonen beteiligt, die sie an der Position 17 des Steroid-Grundgerüstes reduzieren bzw. oxidieren. Verschiedene 17beta-HSDs sind an humanen Erkrankungen beteiligt, z.B. an Pseudohermaphroditismus (17beta-HSD3) oder Zellweger-artigem Syndrom (17beta-HSD4). Außerdem wird den 17beta-HSDs eine Rolle bei der Entstehung und Proliferation von verschiedenen Tumoren zugeschrieben. In dieser Arbeit wird ein neues Evolutionsszenario für die 17beta-HSDs und ihre Verwandten beschrieben. Durch Vereinigung von Proteinstrukturvergleichen und Sequenzvergleichen zu einem einheitlichen Modell war es möglich, einen zuverlässigen Stammbaum der Proteinfamilie zu erstellen. In diesem Stammbaum zeigte sich eine frühe, grundlegende Teilung der 17beta-HSDs in zwei Hauptklassen. Durch Feststellung der Stammbaumwurzel war es möglich den zeitlichen Verlauf der Evolutionsereignisse festzustellen, die zur Entwicklung der Proteinvielfalt in der HSD-Familie geführt haben. Eine umfassende bioinformatische Studie wurde durchgeführt, um die physiologische Funktion der 17beta-HSD Typ 7 festzustellen. Durch Kombination von Expressionsdaten, phylogenetischer Rekonstruktion und Strukturanalysen war es möglich, zu zeigen, dass dieses Östrogen-synthetisierende Enzym wahrscheinlich zuerst an der Cholesterin-Biosynthese beteiligt war, und zwar bei der Reduktion von 3-Ketosteroiden. 17beta-HSD7 ist beim Menschen fast ubiquitär exprimiert und zeigt signifikante Ähnlichkeit mit der 3-Ketosteroid-Reduktase Erg27p aus Hefen. Das Protein fehlt dagegen in Cholesterin-auxotrophen Organismen. Zusätzliches Gewicht erhält diese Vermutung durch die Entdeckung eines spezifischen Promotormoduls, das 17beta-HSD7 mit Proteinen des Cholesterinmetabolismus (IDI1 und MLN64) gemeinsam hat. Anschließende Reaktionen des Cholesterin-Synthesewegs werden von Proteinen katalysiert, deren Mutation zu den Entwicklungsdefekten CHILD-Syndrom und CDPX2-Syndrom führt. Damit ist auch 17beta-HSD7 ein Kandidat für ähnliche Erkrankungen. Durch die Integration von Strukturdaten mit der statistischen Auswertung von Proteinalignments wurden unerwartete konservierte Elemente in der dreidimensionalen Struktur von 17beta-HSD Typ 5 und ihren Verwandten entdeckt. Ein 3D-Modell des Enzyms erm"oglichte es, Struktur-Funktions-Beziehungen von Phytoöstrogenen aufzuklären, die als Inhibitoren der 17beta-HSD5 wirken. Außerdem war es möglich die pH-Abhängigkeit der Inhibition durch Glycyrrhetin-Säure zu erklären. Die notwendigen Methoden zur Evolutionsanalyse großer Datensätze wurden in einer Pilotstudie entwickelt und getestet. Dazu wurde die Evolution der Paired-Box (Pax)-Familie untersucht. Es konnte gezeigt werden, dass der nächste Verwandte dieser Proteine eine Tc1-Transposase ist. Das erste Pax-Protein entstand am Anfang der Metazoen-Evolution durch ein einmaliges Fusionsereignis, bei dem sich die DNA-Bindungsdomäne einer Transposase mit einer Homöodomäne zu einem neuen Transkriptionsfaktor verband. Diesem Fusionsereignis folgte dann eine schnelle Aufspaltung der Familie in mehrere Untergruppen. Durch die Entdeckung der Verwandtschaft mit den Transposasen ist es möglich, nicht nur die Einteilung der Pax-Proteine festzustellen, sondern auch den zeitlichen Ablauf ihrer Evolution zu bestimmen. This work describes the integrative application of various bioinformatic approaches to the family of 17beta-hydroxysteroid dehydrogenases. This protein family is involved in the activation and inactivation of steroid hormones by reduction and oxidation at position 17 of the steroid backbone. Several family members are known to be involved in human disorders (e.g. pseudohermaphroditism or Zellweger-like syndrome) and are implicated in cancerogenesis and tumor proliferation. A reliable evolutionary scenario for the large family of HSD-related proteins was constructed by combining structure-based and sequence-based comparisons into a single phylogenetic tree. The tree indicates a fundamental subdivision of the 17beta-HSDs into two major groups. By determining the root of the phylogenetic tree it was possible to evaluate the time course of evolutionary events leading to the diversity 17beta-HSDs. A comprehensive bioinformatic study was performed to assess the physiological function of human 17beta-HSD type 7. Integrating expression data, phylogenetics and structural analyses it was possible to demonstrate that this estrogenic enzyme probably has an ancestral function in cholesterol metabolism, namely the reduction of 3-ketosteroids. Adjacent steps in the pathway are catalysed by proteins that are mutated in developmental defects (CHILD syndrome and CDPX2 syndrome), making 17beta-HSD7 a likely candidate for similar disorders. The combination of protein structure and statistical evaluation enabled the identification of unexpected conserved structural elements in 17beta-HSD type 5 and its relatives. A 3D-model of the enzyme allowed the explanation of the inhibitory capacity of phytoestrogens acting on 17beta-HSD5. The computer algorithm developed for that purpose is universally applicable and might be used for the structural analysis of other large protein families. The techniques necessary for the evolutionary analysis of large sequence datasets were established and validated in a pilot study on paired-box proteins. It was possible to find the ancestors of the paired-box family among Tc1-transposase proteins. It is shown that paired-box proteins originated at the beginning of metazoan evolution by a single fusion event between a transposase DNA binding domain and a homeobox protein. The fusion event was followed by a rapid diversification of the protein family.

Oestradiol was converted to oestrone about ten time more rapidly by subcellular fractions of normal human endometrium of the secretory phase than by tissue of the proliferative phase. In subcellular fractions of endometrial carcinoma the 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activity decreased with decreasing differentiation of the tumour. Most of the 17beta-HSD activity was located in mitochondrial and microsomal fractions of both normal and neoplastic endometrium. After treatment of patients with gestagens only the well differentiated carcinomata significantly increased in 17beta-HSD activity demonstrating that the hormonal stimulus leads to similar effects on the 17beta-HSD activity as in normal endometrium. Furthermore quantitative aspects of the in vitro binding of 3H-oestradiol and 3H-progesterone to receptor components from normal endometrium and endometrial carcinoma cytoplasmic fractions have been studied. In normal tissue the number of cytoplasmic binding sites for both oestradiol and progesterone varied dramatically during the menstrual cycle: number of oestradiol binding sites were highest during the proliferative phase and fell during the secretory phase; for progesterone site the contrary was the case. In all endometrial carcinomata high oestradiol binding activity was observed. In contrast the number of progesterone sites in the tumours was related to the state of differentiation, which paralled the progestional sensitivity of these tumours.Endometrium samples were taken from 17 women, aged 43-83, who had endometrial tumors, before and after treatment with gestagen preparations. Samples were also taken from 42 women with normal endometria. The 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activity in various fractions of the normal endometria was 10 times higher during the secretory phase than in the proliferation phase. The cytoplasmic estradiol binding receptor molecules (EBRMs) are more prolific at the beginning of the proliferation phase and least frequent in the middle of the secretion phase; the progesterone binding receptor molecule (PBRM) level is inversely proportional to that of the EBRM. In the endometrial tumor tissue, the degree of differentiation of the tumorous tissue determined the 17beta-HSD activity in the various subcellular fractions. Reduction in the differentiation caused reduction in the 17beta-HSD activity. A 3- to 10-fold increase in the 17beta-HSD activity occurred in the well-differentiated tumors after hormonal therapy. High estradiol binding was seen in all of the carcinomata, but the concentration of PBRM increased as differentiation increased or after gestagen treatment was given.

Testosterone 17beta-dehydrogenase can be enriched from Streptomyces hydrogenans. The enzyme dehydrogenizes testosterone with Km=13muM and estradiol-17beta with Km=21muM to the corresponding 17-ketoderivatives. NAD forms NADH with Km=125muM. The enzyme is strongly inhibited by androstandione and 17alpha-methyltestosterone. The Ki for 17alpha-methyltestosterone is 18muM. The enzyme activity increases with increasing pH up to alkali-mediated denaturation at about pH 10. The optimum temperature is at 45 degrees C. If Streptomyces hydrogenans is cultivated in the absence of steroids, the specific activity of testosterone 17beta-dehydrogenase in the cytosol of the microorganisms amounts to 10 mU/mg protein, and increases up to 10-fold if the cells are cultivated in the presence of certain steroids. Testosterone, alpha-dihydrotestosterone, beta-dihydrotestosterone, estradiol-17beta, and 17alpha-methyltestosterone are very effective inducers. Thus, for the first time, the ability of estradiol-17beta to induce an enzyme synthesis in a microorganism is shown. The steroid-dependent induction is inhibited by testosterone acetate and rifamycin SV. Cyproterone, however, does not decrease the testosterone-dependent enzyme induction of testosterone 17beta-dehydrogenase.

Detailed enzyme kinetic parameters of the reactions catalyzed by the two 17beta-hydroxysteroid dehydrogenases (17beta-HSD), which were solubilized from the microsomes of human placenta by treatment with phospholipase A, followed by enrichment and separation were determined. Both enzymes are strictly substrate specific. The most active substrate of one of the 17beta-HSD (fraction A) is estradiol-17beta, the other 17beta-HSD (fraction B) is sensitive to testosterone. Both NAD and NADP can serve as hydrogen transferring coenzymes, the latter giving about one-third of the initial rate of the former. With respect to the influence of temperature, different buffers and pH values, Michaelis constants (Km) with estradiol-17beta and testosterone as substrates, the solubilized and separated microsomal 17beta-HSD behave like those isolated from the cytoplasmic fraction. The two 17beta-HSD, after solubilization from the microsomal fraction of human placenta, enrichment and separation from each other, show only a little activity for the transfer of hydrogen between C17 of estradiol-17beta and C17 of androstenedione. On the other hand, intact microsomes and an integrated system prepared by recombination of the 17beta-enzymes by preincubation in phosphate buffer are able to catalyse very actively the transfer of hydrogen between estradiol-17beta and androstenedione. The effect of temperature and time on the recombination of the two enriched and separated microsomal enzyme activities and the determination of the pH-optimum of the hydrogen transfer reaction are described. Finally it is proposed that the hydrogen transfer between steroid hormones represents an aspect of the true reaction mechanism of steroid hormones: Steroid hormones function as hydrogen transferring coenzymes by forming part of a chain of hydrogen carriers.

The microsomal 3-hydroxysteroid dehydrogenases were solubilized with lubrol, a non-ionic detergent. A 3alpha-hydroxysteroid dehydrogenase is purified about 100-fold by double affinity chromatography on 5alpha-dihydrotestosterone-Sepharose. This enzyme can use both NADH and NADPH as coenzymes.

Histological, histochemical, and electron-microscopic techniques were used to investigate the chorion in 15 women over the first four to eight weeks of normal pregnancy. Evidence was produced to maximum enzyme activity and lipoid accumulation between the sixth and eighth weeks. These findings were confirmed by ultrastructural observation. Data were collected on active exchange in x-cells. That exchange together with manifest delta 5-3-beta hydroxysteroid-dehydrogenase were found to cause not only oxidative processes, but, with some reasonable probability, synthesis of steroid hormones in the chorion, as well.

The enzyme 3 alpha, 20 beta-hydroxysteroid:NAD+ oxidoreductase (EC 1.1.1.53) catalyses the stoichiometric reduction of 20-oxo groups of C-21 steroids by NADH, and the non-stoichiometric oxidation of 3 alpha-hydroxy groups of 5 alpha-androstane derivatives by NAD. The activity of the enzyme towards the most important C-18, C-19 and C-21 steroids of human urine was tested in the presence of NAD and NADH. The rate of reduction of 20-oxo steroids is influenced by substituents at various positions of the steroid skeleton. These studies are intended as the basis of an eventual clinical chemical application.

The surface epithelium of vagina, uterovaginal region and uterus as well as the uterine and uterovaginal glands of 18 mature female quails were studied with histochemical methods. As in other avian species also in the quail a storage of spermatozoa in the lightly coiled uterovaginal glands takes place. The functional specialization of these glands is underlined by their distinct enzyme pattern. A strong reactivity of enzymes from oxidative pathways and of adenosine triphosphatase between epithelium and glandular luminal content. Alkaline phosphatase in the glandular epithelium was observed only when an egg is transported through the uterovaginal region. As in other vertebrate sperm storing sites also in the uterovaginal region of the quail the presence of a strong steroid dehydrogenase activity is registered.

6beta-Methoxy-9beta,10 alpha-pregna-4,6-diene-3,20-dione inhibits the delta4-3-oxosteroid-5alpha-reduction in microsomes and the delta4-3-oxosteroid-5beta-reduction in the soluble fraction of male rat liver. The 3alpha- and 3beta-hydroxysteroid dehydrogenase are not inhibited by these substances.

The adrenogenital syndrome (AGS; congenital adrenal hyperplasia [CAH]) is caused by a congenital defect in biosynthesis of cortisol. It is transmitted by the autosomal recessiv mode of inheritance. Its frequency in Central Europe is about 1:5000 live births, which means two to three times more frequent than phenylketonuria. The following enzyme deficiencies have been described so far: 21-kydroxylase (mild and severe type), 11-hydroxylase, 3-beta-hydroxysteroiddehydrogenase, 17-alpha-hydroxylase, cholesterol desmolase, 18-hydroxylase, 18-dehydrogenase. The clinical symptoms of AGS consist of signs of virilism in girls and macrogenitosomia praecox in boys. In addition, life threatening salt losing crises occur in patients with the severe form of 21-hydroxylase deficiency and the rare cases of 3-beta-hydroxysteroiddehydrogenase and 18-hydroxylase deficiency. The diagnosis should be made as early as possible by a thorough clinical examinations revealing signs of virisism and by the determination of elevated concentrations of androgens in plasma and urine. The therapy consists of substitution of cortisol (hydrocortisone) in the doses of 25--40 mg per m2 body surface per day. If synthetic derivatives are used glucocorticoid equivalent doses must be considered. Regular, short-term follow-ups on outpatient basis are necessary in order to monitor proper growth, bone age development and urinary steroid excretion. On this supposition almost normal growth and development can be achieved in children with AGS. Girls may become fertile following additional corrective surgery. Only in patients with the salt losing form of AGS normal growth appears to be limited despite optimal medical supervision.

On the basis of the "Lipschuetz-ovary" model the rat ovary is cystically altered. -- In such an ovary the effect of a spleen extract (Solcosplen) and FSH (Anternon) were compared with histological and histochemical methods. -- With bothe the substances could be observed a diminution of the cystic degeneration.

A fully enzymatic method to determine total cholesterol in serum is described. The method appears especially suitable for adaptation to discrete mechanical analyzers either of the single channel or the multi-channel type. The method uses the enzymes cholesterol esterase (EC 3.1.1.13), cholesterol oxidase (EC 1.1.3.6) and peroxidase (EC 1.11.1.7) with 4-aminophenazone and phenol as substrates in the indicator reaction. The method was adapted to the Greiner Selective Analyzer GSA-II. For this purpose the critical parameters of the reaction were intensively examined. The complete reagent is stable within the GSA II dispenser at 4 degrees C for at least 1 week. By omitting cholesterol oxidase in the blank reagent a sample bland and a partial reagent blank are obtained. Within a range up to 10.4 mmol/1 (4.0 g/l) the maximum colour is developed within 6 minutes. The calibration factor was stable for 4 months. The method allows absolute measurements. At concentrations between 2 and 4 mmol/1 within-batch precision ranged from 0.5 to 1.4%. Precision from day to day for the same control sera amounted to 2.8; 2.0; 2.7 and 2.0% for a period of 3 months. Examination of accuracy yielded satisfying results. Ascorbic acid in the physiological range did not alter results to a significant extent. Catalase or novaminesulfone added in vitro did not interfere. Optical interferences by bilirubin, hemoglobin or turbidity are compensated by a sample blank. A comparison of results with the enzymatic method of Roeschlau et al. (Z. Klin. Chem. Klin. Biochem. 12, 226 (1974)) yielded satisfactory agreement. The limits of detection of the present method can be lowered by a factor of 2.2 by replacing phenol by dihalogen phenols.

Treatment of human placenta microsomes with phospholipase A or D inhibits the 17beta-hydroxysteroid dehydrogenase (17beta-HSD) activity, parallel with the hydrolysis of membrane phospholipids. The 17beta-HSD activity of phospholipase treated microsomes is reactivated by synthetic phospholipids. The distribution of 17beta-HSD activity in subfractions of original microsomes and of phospholipase treated microsomes obtained by zonal centrifugation was studied. Solubilization of the microsomal 17beta-HSD was achieved by phospholipase A treatment. Two 17beta-HSD were solubilized from human placenta microsomes by phospholipase A treatment and were further purified by ammonium sulphate precipitation, gel filtration on BioGel A-0.5 m, DEAE-Sephadex chromatography and by isoelectric focusing. The enzymes were purified 25.8 and 17.4 times. The isoelectric points and molecular weights of the two 17beta-HSD were determined. Both enzymes are of a 17beta-HSD type. One of the 17beta-HSD, however, was sensitive to estradiol-17beta, the other to testosterone. The question of whether the two enzymes constitute a monomer and a dimer of the same 17beta-HSD or are completely different enzymes, is discussed.

In vitro incubations with slices of two normal human ovaries and 4-14C-pregnenolone as precursor were carried out to study the possibility of a direct influence of chlormadinone acetate on the metabolism of pregnenolone. In agreement with our previous studies the incubations of the ovary from the follicle phase of the cycle yields a profile of steroids different from that of the ovary from the corpus luteum phase of the cycle. Under the experimental condition chosen, the presence of enzymes of the steroidogenic pathway responsible for the synthesis of 17alpha-hydroxy-pregnenolone, DHA, androstenediol (basic metabolites) and androstenedione represents a characteristic profile of steroids of the ovaries from the follicle phase. After the addition of chlormadinone acetate to the incubation medium, the formation of androstenedione was inhibited, whereas the basic metabolites increased. The biosynthesis of progesterone, 17alpha-hydroxyprogesterone, estrone and estradiol represents a characteristic profile of steroids of the ovaries from the corpus luteum phase. After a addition of chlormadinone acetate to the incubation medium, the formation of this characteristic profile of steroids was inhibited. The influence of chlormadinone acetate on the two different profiles of steroids indicated, that chlormadinone acetate exerts an inhibitory effect on the 3beta-hydroxysteroid-dehydrogenase-delta5-4-isome

The study aimed to find out the effect of sulfonamide combined with Trimetaprim-Biseptol 480 on the adrenal cortex in post-operative shock after removal of SPIGELian lobe (lobectomy of the lobus caudatus and unilaterally of one kidney with its suprarenal gland. The study was performed on a material of white rats which were post-operatively administered Biseptol 480 in doses 5 times bigger than those given to men. It was attempted to determine histochemically the intensity of the adrenal cortex' function by testing the number of lipid droplets, activity of the main enzyme of steroidogenesis (beta-hydroxy steroid dehydrogenase) and the level of alpha-ketols (as the final stage of steroidogenesis). Pathomorphologic examinations were also performe. On the basis of the present study's results, it was observed that - in the case of liver-lobectomy - the zona fasciculata and zona reticularis are functionally stimulated but the zona glomerulosa becomes insufficient. In the case of nephrectomy plus suprarenal gland's removal, all the adrenal cortex becomes insufficient. Administration of Biseptol in the 1st case contributed to hormonal inactivation of the zone glomerulosa cells, but in the 2nd case, it caused an increased activity of steroid dehydrogenase and an increase of the alpha-ketol level in the zona fasciculata.

By histochemical and histometrical methods the the effect of l-triiodothyronine on the zona glomerulosa from rat adrenal cortex was investigated. Glucose-6-phosphatedehydrogenase and 3-beta-OH-steroiddehydrogenase activities were determined in slices of adrenal cortex. No increase in activities of these enzymes was observed after treatment with l-triiodothyronine. In contrast, histometrical studies showed a significant enlargement of nuclei in the zona glomerulosa as well as in the zona fasciculata. This observation suggests enhanced secretory activity of both zones of the adrenal cortex of the rat.

The enzymic determination of total cholesterol described by P. Röschlau (Z. Klin. Chem. Klin. Biochem. 12, 403-407 (1974)) was modified and adapted to the Centrifichem system. The method which requires only 5 mul serum, is accurate, quick and simple. A separate serum blank is not necessary. Compared with the manual method, smaller quantities of reagents used and the resulting decrease in cost are appreciable for large series of analyses. The course of the reaction at 30 and 37 degrees C, the linearity, calibration, precision, recovery, and correlation with the Lieberman-Burchard method and the enzymic manual method are described.

The advantages of enzymatic analysis compared to conventional methods are shown by an example of a simplified, fully enzymatic cholesterol determination. They are: high analytical precision, reagents which are easy to handle, no inhibition be metabolites. The poor correlation between enzymatic and chemical analysis requires new normal values. The following are recommended for cholesterol: normal up to 200 mg/dl, requiring control 200-250 mg/dl and pathological over 250 mg/dl.

Effects of chlormadinone acetate on the ovary were studied in 20 female Wistar rats. Chlormadinone was started on the 1st day of diestrus and given for 20 days; animals were killed 24 hours after the last administration. Examination of ovary sections revealed hyperplastic interstitial gland, a decreased number of corpora lutea and an increased number of atretic follicules. Histochemical studies indicated increased interstitial gland activity and full activity of atretic follicules.

After application of TSH, trijodthyronine and thyroxine enzyme histochemical investigations were carried out on the Harderian glands of albino rats and guinea pigs. Marked changes were seen after a treatment of 9 days with TSH. Thereby in B-cells of rat appeared big vacuoles, which were clearly to be seen after oxidoreductase-reactions, but hardly to be seen after hydrolase-reactions. In guinea pigs the cells of the gland are strongly vacuolised both in controls and in treated animals. But this last group shows a great hypertrophy of the gland with widening of tubuli and acini. In both species of animals the steroid-3-beta-ol-dehydrogenase-reaction is negative. Nomenclature, specific reactions of the animals treated with hormones, function of the Harderian gland and its relevance in investigations of experimental exophthalmos are discussed.

The immunologic relations between mother, foetus and placenta are discussed and those antigens of the human placenta already characterized by their physico-chemical and immunochemical properties described. In diagnostics the detection and determination of placental proteins is used in pregnancy tests, for the evaluation of placental functions and the detection of malignant diseases. Antibodies to placental antigens have an abortive effect; immunization against placental specific proteins may have implications as an immunologic contraceptive method and for the immunotherapy of choriocarcinoma.The immunologic relationships of mother, fetus and placenta are discussed, and the human placental antigens already characterized by their physico-chemical and immunological properties are described. The detection and determination of placental proteins is used in pregnancy tests, for the evaluation of placental function, and in the diagnosis of malignant disease. Antibodies to placental antigens have an abortive effect; immunization against placental specific proteins may have implications as an immunologic contraceptive method and for the immunotherapy of choriocarcinoma.

In order to study some aspects of the steroid hormone balance in old age the following organ functions of young and senescent male and female animals were investigated: 1) The capacity of testicular (45, 68-75 and 900 day-old animals) and ovarian tissue homogenates (29, 45, 66 and 900 day-old animals) to metabolically transform the sex hormone precursor, progesterone. 2) The capacity of liver slices (60-90 and 900 day-old animals) to generate a sex-specific metabolite pattern during incubation with testosterone. 3) The activities of some enzymes of steroid metabolism, which normally show sex differences in liver cell fractions (60-90 and 900 day-old animals). The testicular capacity of senescent animals to synthesize 17 alpha-hydroxyprogesterone, androstenedione and testosterone (main pathway of androgen biosynthesis) is drastically reduced compared to that of young adult rats; the reduction also extends to the production of highly polar C19O3- and C21O3-steroids. In contrast to these deficiencies, conversion of progesterone to 20 alpha-dihydroprogesterone increases in old age, whereas the generation of 5 alpha-hydrogenated compounds from testosterone and androstenedione remains unchanged. If the group of adolescent 45 day-old animals is also taken into consideration, then the biosynthetic sequence from progesterone to testosterone exhibits a biphasic developmental course. Production rates rise from low levels only to fall back to lower rates of synthesis in old age. In no age group can the production of oestrogens in measurable quantities be detected. However, 5 alpha-hydrogenated C19O2-steroid metabolites are detected, albeit only in prepuberal animals. After puberty only progesterone, 20 alpha-dihydroprogesterone and the 5 alpha-pregnane derivatives of these two steroids can be demonstrated. The pattern of the respective metabolites undergoes an age-dependent metabolite-specific development ending (900 day-old animals) with minimal yields of products (less than 21% of progesterone is converted). The production of hydroxylated metabolites (highly polar C21O3-steroid fraction) decreases very early in life (between day 29 and 45) to values indistinguishable from those of old animals. The sexually highly differentiated metabolite pattern of hepatic testosterone metabolism typical of young adult animals (60-90 day-old) is not prominent in old age. Both sexes exhibit a retarded testosterone turnover due to a decrease in the hydroxylating activity (males being more affected than females) and a deficiency of 5 alpha-hydrogenation (females only).(ABSTRACT TRUNCATED AT 400 WORDS)