Androgen production by testes of Gallus domesticus during postembryonic development

Cock testes incubated with labeled pregnenolone or progesterone as substrates produced testosterone as the main compound. The formation of 17α-hydroxyprogesterone was greater with progesterone as precursor, but the production of radioactive 20β-dihydroprogesterone and androstenedione was similar with either substrate. Testes from 1-, 21-, and 40-day-old chicks incubated with progesterone as a substrate had a very low testosterone: androstenedione production ratio (0.05). In mature animals, however, more testosterone than androstenedione was produced from radioactive progesterone and the production ratio testosterone: androstenedione was 24.     

The in vitro biosynthesis of steroids by the gonad of the cuttlefish (Sepia officinalis L.)

In vitro steroid biosynthesis in the male and female gonads of Sepia officinalis was investigated. Using tritium- and ¹⁴C-labeled precursors, seven enzyme systems were demonstrated: a C_20,22-lyase (cholesterol→pregnenolone), a 3β-hydroxysteroid dehydrogenase-Δ_5?4-isomerase complex (pregnenolone → progesterone; 17α-hydroxypregnenolone → 17α-hydroxyprogesterone; dehydroepiandrosterone → androstenedione), a 17α-hydroxylase (pregnenolone → 17α-hydroxypregnenolone; progesterone → 17α-hydroxyprogesterone), a C_17,20-lyase (17α-hydroxypregnenolone → dehydroepiandrosterone), a 17β-hydroxysteroid dehydrogenase (dehydroepiandrosterone → androstenediol; androstenedione → testosterone; estrone→estradiol-17β), a 20α-ol dehydrogenase (progesterone→20α-dihydroprogesterone), and a 20β-ol dehydrogenase (progesterone→20β-dihydroprogesterone). The yields were rather low (0.01–3%), except when pregnenolone was used (8%). Radioimmunoassay techniques indicate the presence of testosterone in the plasma of the cuttlefish but the absence of estrogens.     

In vitro biosynthesis of steroids from progesterone by the ovaries and pyloric ceca of the starfish Asterias rubens

In vitro biosynthesis of steroids from progesterone in ovaries and pyloric ceca of Asterias rubens has been investigated. The biosynthesis of 17α-hydroxyprogesterone, androstenedione, testosterone, 20α-dihydroprogesterone, 11-desoxycorticosterone, and 5α-pregnane-3,20-dione could be demonstrated to take place in the tissues of both organs by using [1,2-³H]progesterone as a precursor. The yields of intermediates of the Δ⁴-pathway and of 11-desoxycorticosterone are small, being higher in the ovaries than in the pyloric ceca. The yields of 20α-dihydroprogesterone are low, those of 5α-pregnane-3,20-dione are high. In both cases the yields in the pyloric ceca exceed those in the ovaries. The results indicate the presence of the following biosynthetic enzyme systems in ovaries and pyloric ceca of Asterias rubens: 17α-hydroxylase, C₁₇C₂₀-lyase, 17β-HSD, 20β-HSD, 21-hydroxylase, and 5α-reductase. The importance of these enzymes for the metabolism of progesterone, i.e., the biosynthesis of C₁₉-steroids, 20α-dihydroprogesterone, and corticosteroids, will be discussed.     

Evidence of the in vitro formation of cortisol by the adrenal gland of embryonic and young chickens (Gallus domesticus)

The aim of this study is to elucidate the ontogenetic aspect of corticosteroidogenesis in the chicken. The adrenal gland of embryonic and very young chicks contains an enzyme system which converts progesterone to 17α-hydroxyprogesterone. 4-¹⁴C-Labeled cholesterol, pregnenolone, progesterone, and 17α-hydroxyprogesterone were incubated with the homogenates of adrenal gland from 17- and 21-day-old chick embryos and chickens. The metabolic products were identified by their mobilities on a thin-layer chromatogram and recrystallization to constant ³H:¹⁴C ratio after adding the corresponding ³H-labeled steroid. Cholesterol was metabolized to pregnenolone in the tissue homogenates from chick embryos and chickens at all ages. Pregnenolone was metabolized to progesterone, 11-deoxycorticosterone, and other minor metabolites, but not to 17α-hydroxyprogesterone. The major products from progesterone were 11-deoxycorticosterone and 17α-hydroxyprogesterone. The yield of 17α-hydroxyprogesterone decreased with advancing age and became zero at 7 days posthatching. 11-Deoxycortisol and cortisol were produced from progesterone by the homogenates from 17- and 21-day-old embryos and 3-day-old chicks, but neither was produced by those from 7-day-old chicks or those from 150-day-old hens. Radioactive 17α-hydroxyprogesterone was converted to 11-deoxycortisol and cortisol in large amounts and to cortisone in small amounts. Androstenedione and testosterone were detected in the adrenal homogenate from 17 days of incubation to 7 days posthatching, but not in the tissue from 14 days posthatching. The activity of 17α-hydroxylase was high at 17 days of incubation, decreasing with advancing age, and disappeared between 7 and 14 days posthatching. These results represent definite evidence of cortisol and testosterone formation in vitro by embryonic and very young chick adrenals.     

The in vitro biosynthesis of steroids by the gonad of the mussel (Mytilus edulis)

In vitro steroid biosynthesis in the male and female gonad of Mytilus edulis was investigated. Using tritium and ¹⁴C-labeled precursors, four enzyme systems were demonstrated: a 3β-hydroxysteroid dehydrogenase-Δ_5,4-isomerase comples (pregnenolone→progesterone; 17α-hydroxypregnenolone→17α-hydroxyprogesterone; dehydroepiandrosterone→androstenedione), a C_17,20-lyase (17α-hydroxypregnenolone→dehydroepiandrosterone; 17α-hydroxyprogesterone→androstenedione), a 17β-hydroxysteroid dehydrogenase (dehydroepiandrosterone→androstenediol; androstenedioneαtestosterone; estradiol-17βαestrone) and a 5α-reductase (testosterone→5α-dihydrotestosterone). The yields were very low (0.2–1%) except when estrogens were used (10–50%). Radioimmunoassay techniques indicate the presence of testosterone and possibly estrogens in the gonad of the mussel at two different stages in its gametogenic cycle.     

Steroid biosynthesis by the testes of the dogfish Scyliorhinus caniculus

Dogfish testes were incubated with radioactive progesterone, pregnenolone, and testosterone, and both free and conjugated metabolites were examined. In the free fraction, which contained 42–70% of the incubated radioactivity, progesterone, androstenedione, and testosterone were identified as incubation products of both progesterone and pregnenolone. In addition, a small amount of 17α-hydroxyprogesterone was identified as a metabolite of progesterone in one fish. Testosterone and androstenedione were the only free steroids isolated from incubations of testosterone. Although steroid glucuronide formation was insignificant, very large amounts of solvolysable steroids were isolated from all incubations. With pregnenolone and progesterone, 10–30% of the incubated radioactivity was recovered in this solvolysable fraction, in which the major products were identified as testosterone and 17α,20β-dihydroxy-4-pregnen-3-one. With two fish incubated with [¹⁴C]testosterone, 5α-androstane-3β, 17β-diol was isolated in low yield from the solvolysable fraction in addition to testosterone, but in one incubation with [³H]testosterone, the sole component of this fraction was testosterone which accounted for 21% of the initial radioactivity.     

Formation of 5alpha-reduced C19-steroids from progesterone in vitro by a pathway through 5alpha-reduced C21-steroids in ovaries of late prepubertal rats.

Ovarian homogenates from 10-150-day-old rats were incubated with [3H]progesterone and NADPH. Also, ovarian homogenates from 28-day-old rats were incubated for 5-180 min with either [14C]progesterone, [3H]5alpha-pregnane-3,20-dione or [14C]progesterone plus [3H]5alpha-pregnane-3,20-dione. Following incubation, radioactive metabolites were isolated, identified, and measured by column and paper chromatography, with derivative formation and recrystallizations to constant specific activity. Prepubertal ovaries (10, 20, and 28 days of age) converted 15-60% of progesterone to C21-17-hydroxysteroids and C19-steroids. At 40 and 150 days of age (postpubertal), the formation of these steroids decreased to less than 2%. At 10 and 150 days of age, the major C19-steroids formed from progesterone were androstenedione and testosterone. At 20 and 28 days of age, however, no accumulation of these C19-delta4-3ketosteroids was found (less than 0.1% of each), at which time the conversion of progesterone to 5alpha-reduced C19-steriods, such as androsterone and 5alpha-androstane-3alpha,17beta-diol, reached 30%. In ovaries of 28-day-old rats, the results from incubation studies for the detection of metabolic pathways indicated two biosynthetic pathways leading to 5alpha-reduced C19-steroids, one from progesterone via 5alpha-reduced C21 steroids, such as 3alpha-hydroxy-5alpha-pregnan-20-one and 3alpha,17alpha-dihydroxy-5alpha-pregnan-20-one, and a second via 17-hydroxyprogesterone, androstenedione, and testosterone. It seems that the active 5alpha-reduction of C19-delta4-3-ketosteroids and the formation of 5alpha-reduced C19-steroids by the pathway through 5alpha-reduced C21-steroids, are present in the ovaries of older prepubertal rats and may be the biological significance.     

Biosynthesis of 15-hydroxylated steroids by gonads of the river lamprey, Lampetra fluviatilis,in vitro

Ovaries and testes of the river lamprey, Lampetra fluviatilis, were incubated with [³H]testosterone and [³H]progesterone and the major metabolites identified by chromatography, chemical reaction, and gas chromatography-mass spectrometry. The major metabolite of progesterone with gonads of both sexes was 15α-hydroxyprogesterone (26.6% yield in ovary, 50.0% in testis); a small amount of 15β-hydroxyprogesterone was also found in the testis incubation. With testosterone as substrate, the major metabolite was 15β-hydroxytesterone (84.8% in testis, 65.2% in ovary). The formation of androstenedione, but not of testosterone, from progesterone was also demonstrated in both sexes.     

Testicular steroidogenesis in the mature and immature baboon Papio anubis.

The following studies were undertaken to compare testicular steroidogenesis in the mature and immature baboon. Testicular fragments (50 mg) were incubated for 3 hr with [7-³H]pregnenolone, or with [7-³H]progesterone. The mature testis formed more testosterone (4.6%), androstenedione (1.6%), and progesterone (28.5%) from pregnenolone than did the immature testis (0.6, 0.5, and 26.1%). The immature testis formed more 17α-hydroxyprogesterone (34.7%) and 20α-dihydroprogesterone (23.2%) from pregnenolone than did the mature testis. Similar conversions were obtained in progesterone incubates. 5α-Androstanediol was identified only in mature incubates. These results suggest that the mature baboon testis has greater C₁₇-C₂₀ lyase, 17β-hydroxysteroid dehydrogenase, and 5α-reductase activities than the immature testis, while the immature testis has greater 20α-reductase activity.     

Biosynthetic pathways of testosterone and estradiol-17 beta in slices of the embryonic ovary and testis of the chicken (Gallus domesticus)

To elucidate synthetic pathways of testosterone and estradiol-17 beta in embryonic gonads of the chicken, metabolism of various 14C-labeled steroids in slices of the left ovaries and paired testes of 15- and 9-day-old chicken embryos was examined. (1) Fifteen-day-old chicken embryos: From pregnenolone, more 17 alpha-hydroxypregnenolone was produced than progesterone in the ovary, while more progesterone was produced than 17 alpha-hydroxypregnenolone in the testis. From 17 alpha-hydroxypregnenolone, however, only dehydroepiandrosterone was detected as a product in both gonads. Dehydroepiandrosterone was converted mainly into androstenedione and its 5 beta-reduced derivatives by both gonads. Progesterone was converted into 5 beta-pregnane-3,20-dione more than into 17 alpha-hydroxyprogesterone by both gonads. Both gonads metabolized 17 alpha-hydroxyprogesterone, androstenedione, and testosterone predominantly into their corresponding 5 beta-reduced steroids, while production of androstenedione from 17 alpha-hydroxyprogesterone and of testosterone from androstenedione was limited. Estradiol-17 beta was produced from androstenedione and testosterone only by the ovary. (2) Nine-day-old chicken embryos: From pregnenolone, production of progesterone and 17 alpha-hydroxypregnenolone was similar in the ovary. On the other hand, in the testis, more progesterone was produced than 17 alpha-hydroxypregnenolone from pregnenolone. For delta 4-3-oxo steroids, strong activity of 5 beta-reductase was demonstrated in both gonads. From these results, both delta 4- and delta 5-pathways are involved in the formation of testosterone and then finally of estradiol-17 beta by the embryonic gonads of the chicken, and relative preference for the pathway seems to depend on sexes and embryonic ages. In addition, it is suggested that steroidogenesis in these embryonic gonads is characterized by marked activity of 5 beta-reductase, irrespective of sexes or ages.     

Site at which FSH regulates estradiol-17beta biosynthesis in Sertoli cell preparations in culture.

Sertoli cells were isolated from testes of 20-day-old rats and were maintained in primary culture. The ability of these cells to synthesise estradiol-17beta from a variety of exogenous substrates, progesterone, testosterone,androstenedione, 19-hydroxyandrostenedione and 19-hydroxytestosterone in the presence and absence of follicle-stimulating hormone (FSH) was examined. In the presence of each of the substrates alone for 24 h the rate of estradiol-17beta synthesis was very low. FSH (NIH-FSH-S11, 5 mug/ml) stimulated estradiol-17beta synthesis 75-fold when added to medium containing testosterone (5 X 10(-7)M) but caused only marginal stimulation when added to medium containing progesterone (5 X 10(-7) M). Both FSH and dibutyryl cyclic AMP (bu2cAMP) stimulated the conversion of each of the substrates, androstenedione, 19-hydroxyandrostenedione and 19-hydroxytestosterone to estradiol-17beta, and the effects were similar to those observed in the presence of testosterone. These data indicate that, under the culture conditions employed, progesterone is not an effective substrate for conversion to estradiol-17beta by Sertoli cells. Estradiol-17beta synthesis was stimulated by FSH in the presence of the C19 steluences the conversion of androgens to estrogens, either directly or indirectly, at the aromatisation step (i.e. the conversion of 19-hydroxylated androgens to estrogens).     

Pathways of testosterone synthesis in decapsulated testes of mice.

In order to study the temporal relations in the biogenesis of testosterone, decapsulated testes of adult mice were incubated with carbon-14-labelled sodium acetate and attempts were made to isolate the most likely intermediates. Considerable quantities of radiochemically homogeneous squalene, lanosterol, cholesterol, testosterone and androstenedione, but no pregnenolone, progesterone, 17-hydroxypregnenoline, 17-hydroxyprogesterone, dehydroepiandrosterone, pregnenolone sulphate or dehydroepiandrosterone sulphate were isolated. The same pattern of incorporation was found when gradually increasing amounts of non-labelled pregnenolone, progesterone, 17-hydroxypregenenolone, 17-hydroxyprogesterone, dehydroepiandrosterone, dehydroepiandrosterone sulphate or testosterone were added to the system as "trapping agents" or when Leydig cell preparations rather than decapsulated testes were used. The presence of 10 mIU of HCG greatly enhanced the de novo formation of testosterone, androstenedione and 5alpha-dihydrotestosterone but did not change the pattern of acetate incorporation. Radioimmunoassays of the incubation medium with or without added HCG, and carried out at different periods of time indicated the presence of gradually increasing amounts of testosterone and androstenedione together with some 5alpha-dihydrotestosterone, whereas only trace amounts of pregnenolone, progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone and dehydroepiandrosterone were present. An analysis of the incubated testes revealed that the addition of HCG significantly enhanced the content of testosterone, androstenedione and 5alpha-dihydrotestosterone. Little or no increase was observed as far as pregnenolone, progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone or dehydroepiandrosterone were concerned. It is concluded that decapsulated testes of mice synthesize de novo testosterone from sodium acetate under conditions in which the formation of pregnenolone, progesterone, 17-hydroxypregnenolone, 17-hydroxyprogesterone, pregnenolone sulphate and 17-hydroxypregnenolone sulphate cannot be demonstrated.     

Studies on the reproductive cycle on the female cobra, Naja naja. II. In vitro ovarian steroid synthesis.

The synthesis of steroids in vitro by minced ovarian tissue from the cobra, Naja naja, using [³H]pregnenolone and [³H]dehydroepiandrosterone([³H]DHA) as precursors was studied. From [³H]pregnenolone the major products were progesterone, pregnanolone (3α-hydroxy-5β-pregnan-20-one), 17α-hydroxyprogesterone, androstenedione, and testosterone. DHA and 17α-hydroxypregnenolone were tentatively identified, but insufficient material was available for positive characterization. From incubations using [³H]DHA as precursor, the only products identified were testosterone, androstenedione, and estradiol-17β. Significant amounts of radioactivity were associated with an estriol fraction from both the pregnenolone and the DHA incubations but were not further characterized. Time-lapse studies revealed an extremely rapid conversion of [³H] pregnenolone to progesterone, with a maximum occurring after 15 min in tissue taken from a cobra in April at the height of the reproductive period. Addition of cofactors to the medium markedly stimulated the synthesis of progesterone and pregnanolone from [³H]pregnenolone, but appeared to inhibit the production of other ovarian steroids. Mammalian LH, when added to the incubation medium, was found to stimulate the biosynthesis of 17α-hydroxyprogesterone, androstenedione, and testosterone from [³H]pregnenolone. Addition of fresh, homogenized snake pituitary or mammalian FSH appeared to increase the yield of testosterone but none of the precursors in the pathway, and there was a suggestion that FSH alone increased the rate of aromatization.     

Effect of androgens on the biosynthesis of estradiol-17beta by isolated periovulatory rat follicles.

To analyse the mechanism for the earlier reported decline in estrogen synthesis by the periovulatory rat follicle, prepubertal rats injected with 8 IU PMS on day 28 were killed following the endogenous gonadotrophin surge (15.00–18.00) on day 30. Isolated preovulatory follicles were incubated for 2 h in a chemically defined medium. Steroids were measured by specific RIA methods. Follicles exposed in vivo to the gonadotrophin surge and extirpated 19.00–22.00 h on day 30 secreted significantly lower amounts of androstenedione, testosterone and estradiol-17β but significantly higher amounts of progesterone than did follicles extirpated from rats in which the gonadotrophin surge had been prevented by a Nembutal injection. Secretion of estradiol-17β by follicles isolated following the endogenous gonadotrophin surge remained low when LH, FSH or dibutyryl cyclic 3′,5′-AMP was added to the medium. However, the addition of testosterone (0.1–1 μg/ml) or androstenedione (1 μg/ml) to the incubation medium restored estradiol biosynthesis to values similar to those seen prior to gonadotrophin exposure. There was no effect of 5α-dihydrotestosterone or 17α-hydroxyprogesterone on the estradiol-17β synthesis. The results indicate that cleavage of the 17:20 sidechain rather than the aromatase enzyme limits estradiol synthesis in the periovulatory follicle following the gonadotrophin surge. It is suggested that the combined action of LH and FSH of the gonadotrophin surge might explain the lack of inhibitory effect on the aromatase enzyme recently reported by Katz and Armstrong (1976) 6–8 h after the injection of LH.     

In vitro metabolism of 4-pregnenes in ovaries of a freshwater teleost,the ayu (Plecoglossus altivelis): Production of 17α,20β-dihydroxy-4-pregnen-3-one and its 5β-reduced metabolites,and activation of 3β- and 20β-hydroxysteroid dehydrogenases by treatment with a fish gonadotropin

In vitro steroidogenesis in the mature ovaries of a freshwater teleost, the ayu (Plecoglossus altivelis), was examined. Cell-free homogenates of the ovaries of untreated fish or fish treated with a salmon gonadotropin (SG-G100) were aerobically incubated with ¹⁴C-labeled progesterone, 17α-hydroxyprogesterone, or 17α,20β-dihydroxy-4-pregnen-3-one, in the presence of NADPH. (1) Untreated fish: Progesterone was converted to 3α,17α-dihydroxy-5β-pregnan-20-one (the major product), 17α-hydroxyprogesterone, testosterone, 3α-hydroxy-5β-pregnan-20-one, 17α-hydroxy-5β-pregnane-3,20-dione, 17α,20β-dihydroxy-5β-pregnan-3-one, and 5β-pregnane-3α,17α,20β-triol. 17α-Hydroxyprogesterone was also transformed to 3α,17α-dihydroxy-5β-pregnan-20-one (the major product), in addition to the above-stated metabolites. 17α,20β-Dihydroxy-4-pregnen-3-one was metabolized into 17α,20β-dihydroxy-5β-pregnan-3-one and 5β-pregnane-3α,17α,20β-triol. (2) Fish treated with the gonadotropin: Besides the metabolites mentioned above, 17α,20β-dihydroxy-4-pregnen-3-one was confirmed as a metabolite of progesterone, and enhanced production of 17α,20β-dihydroxy-5β-pregnan-3-one and 5β-pregnane-3α,17α,20β-triol was observed. 17α-Hydroxyprogesterone was transformed to 17α,20β-dihydroxy-4-pregnen-3-one and 5β-pregnane-3β,17α,20β-triol, in addition to the metabolites obtained by the untreated fish, and formation of 17α,20β-dihydroxy-5β-pregnan-3-one and 5β-pregnane-3α,17α,20β-triol was increased. 17α,20β-Dihydroxy-4-pregnen-3-one was converted into 5β-pregnane-3β,17α,20β-triol besides 17α,20β-dihydroxy-5β-pregnan-3-one and 5β-pregnane-3α,17α,20β-triol. From these results it is concluded that, by the treatment of the fish with gonadotropin, ovarian 3β- and 20β-hydroxysteroid dehydrogenases were selectively activated.     

Androgen biosynthesis by marmoset testes in vitro.

These studies were undertaken to determine the major steroid metabolites formed from selected androgen precursors by the testis of the marmoset, Saguinus oedipus, a New World primate of the family Callitricadae. Testicular fragments (50 mg) were incubated for 3.0 hr with pregnenolone-7-³H or with progesterone-7-³H. The major metabolites formed from pregnenolone were 17α-hydroxyprogesterone (42.7%), testosterone (20.5%), androstenedione (11.4%) and progesterone (9.2%). Nonmetabolized substrate was 6.8% of radioactivity. For porgesterone incubations, 17α-hydroxyprogesterone was the major matabolite (49.0%), with testosterone (21.2%) and androstenedione (10.7%) as lesser metabolites. Unreacted progesterone accounted for 14.9% of all radioactivity. The unusually high levels of 17α-hydroxyprogesterone in marmosets is in contrast to that observed in other mammalian species.     

Biochemical, histochemical, and ultrastructural analyses of presumed steroid-producing tissues in the sexually mature sea lamprey, Petromyzon marinus L

In vitro incubations of testicular, ovarian, and presumed adrenocortical tissues (PAT) from the mature sea lamprey, Petromyzon marinus, with [1,2-³H]cholesterol failed to form cortisol, cortisone, corticosterone, 11-deoxycortisol, 11-deoxycorticosterone, 17α-hydroxypregnenolone, 17α-hydroxyprogesterone, pregnenolone, and progesterone. “Isopolarity” and “isomorphicity” were establidhed for testosterone and androstenedione from the PAT incubation, but subsequent attempts at derivative formation indicated that no testosterone or androstenedione was formed. The interstitial cells of the testes and the cells within the ovarian follicles of P. marinus have a fine structure similar to those in other species of lamprey. The appearance of these tissues and of PAT remains unaltered after 4 hr of incubation. Histochemical procedures did not provide evidence for 3β-hydroxysteroid dehydrogenase (3β-HSD) activity in ovary and PAT, and only a weak 3β-HSD activity was observed over the interstitial tissue of the testes. Spectrophotometric evidence for 3β-HSD activity was obtained from PAT and testicular tissue homogenates. No 3β-HSD activity was observed in mature ovarian tissue homogenates.     

In vitro study of liver glycogen phosphorylase in rainbow trout. Control by glucose, corticoids, adrenaline and glucagon

Gonads of 2.0- to 20.5-day-old chick embryos and 1-day posthatch chicks (Day 21.5) were examined immunocytochemically for the presence of estrone and 17β-estradiol. Both estrone and 17β-estradiol were first observed in approximately equal amounts in the interstitial cells of indifferent gonalds of both sexes on Day 3.5 of incubation. This is 3.0 days prior to the morphological differentiation of these gonads into either testes or ovaries on Day 6.5. On Day 6.5 estrone first appeared in the medullary (primary) cords of all gonalds, at which time left ovaries exhibited a greater amount of estrone and 17β-estradiol than did testes. Day 13.5 was the time of initial appearance of estrone and 17β-estradiol in the cortical (secondary) cords and cortical interstitial cells of left ovaries. Estrone was the predominant estrogen synthesized by left ovaries and testes throughout embryonic development. Also, estrone and 17β-estradiol were synthesized in greater quantities by left ovaries than right ovaries or testes. Results are discussed in terms of Wolff's and Willier's theories of gonadal sex differentiation, as well as the growth profile of the female left Müllerian duct.     

In VitroBiosynthesis of Androgens in the Australian Lungfish,Neoceratodus forsteri

The serum concentration of testosterone was estimated from a population of wild lungfish over 6–7 years of sampling. Male lungfish were found to have high circulating levels of testosterone (∼50 ng/ml) which varied seasonally and could be correlated with spermatogenesis as judged by testis histology. Incubation of testis tissue slices with [³H]progesterone, [³H]17-hydroxyprogesterone, or [³H]testosterone confirmed that testosterone is the major androgen inNeoceratodus.Not even trace amounts of 11-keto- or 11β-hydroxytestosterone or 5α-dihydrotestosterone could be identified by TLC separations. There was little or no conjugation of steroids by the testes, except during the spawning season, when glucuronides of androstenedione and testosterone were produced.     

Steroid biosynthesis by ovarian follicles of Xenopus laevis in vitro during oogenesis

In vitro steroid metabolism was investigated in Xenopus laevis vitellogenic follicles (0.8 mm ? diameter ? 1.0 mm) and full-grown follicles (diameter ? 1.2 mm); in both classes of follicles pregnenolone was transformed to progesterone and progesterone itself was further metabolized to 4-en-3-ketosteroids. The 3β-hydroxysteroid dehydrogenase activity was restricted to follicular cells. Xenopus laevis follicles catalyze the conversion of androstenedione and testosterone to estradiol-17β and estrone, respectively. Generally 10 to 50 times more estrogens were found to be associated with follicular envelopes. Ovarian follicles also metabolized estrone to estradiol-17β; there was only minimal conversion of estradiol to estrone. In vitro purified Acipenser gonadotropic hormone induced a 60% inhibition of the conversion of androstenedione to estrogens.