Steroid metabolism in the testes of the African catfish, Clarias gariepinus (Burchell), during spawning season, under natural conditions and kept in ponds

Steroid metabolism in the testes of Clarias gariepinus, collected in the Hula nature reserve and a fish pond in North Israel during the spawning season, was studied in vitro by homogenate and tissue incubations with [3H]pregnenolone or [3H]androstenedione as precursors. It could be demonstrated that [3H]pregnenolone was mainly converted via progesterone and 17 alpha-hydroxyprogesterone into androstenedione, 11 beta-hydroxyandrostenedione, and 11 beta-hydroxytestosterone. The final products from [3H]androstenedione incubations, 11 beta-hydroxyandrostenedione, and 11 beta-hydroxytestosterone, confirm these findings. The major difference in steroid metabolism between wild and pond animals was a reduction in androgen synthesis in the first group, resulting in higher amounts of C21-steroids. Moreover, the synthesis of two steroid esters, including pregnenolone ester, could be established with tissue incubations of wild animals only. Steroid conjugates were hardly synthesized at all in the testes of C. gariepinus.     

Steroid metabolism in the seminal vesicles of the African catfish, Clarias gariepinus (Burchell), during the spawning season, under natural conditions, and kept in ponds

Steroid metabolism in the seminal vesicles of Clarias gariepinus, collected in the Hula nature reserve and in a fish pond in North Israel during the spawning season, was studied in vitro by homogenate and tissue incubations with [3H]pregnenolone, [3H]dehydroepiandrosterone, or [3H]androstenedione as precursor. The seminal vesicles were able to synthesize androgens, 11-oxygenated androgens, and 5 beta-reduced C19- and C21-steroids; a pregnenolone ester was also formed. Furthermore a potent synthesis of steroid glucuronides, i.e., the glucuronides of testosterone, 5 beta-dihydrotestosterone, 5 beta-androstan-3 alpha, 17 beta-diol, and etiocholanolone, was observed. When reared in ponds, the African catfish fails to spawn. This might be caused by a change in steroid glucuronide (pheromone) production by the seminal vesicles, as it appeared that the synthesis of glucuronides differs in "wild" and "pond" animals. Etiocholanolone glucuronide is completely absent in pond animals.     

Quantitative analysis of steroids and steroid glucuronides in the seminal vesicle fluid of feral spawning and feral and cultivated nonspawning African catfish, Clarias gariepinus

The seminal vesicles of African catfish, Clarias gariepinus, can produce at least seven different steroid glucuronides, especially during the breeding season. In the present experiments quantification of the seven compounds and their free steroids was carried out by means of gas chromatography-mass spectrometry in particular by selected ion monitoring, using seminal vesicle fluid of African catfish collected in the Hula nature reserve (Israel) and from a nearby fish farm. Some of the feral fish were in spawning condition; the others and the pond fish were in nonspawning condition. Compared to the nonspawning groups, in the feral spawning animals a significantly higher level was found especially of 5 beta-pregnane- 3 alpha,17 alpha-diol-20-one-glucuronide, but also of 5 beta-androstane-3 alpha,17 beta-diol-glucuronide, 5 beta-androstane-3 alpha,17 beta-diol-11-one-glucuronide, and 5 beta-pregnane-3 alpha,17 alpha-diol-20-one. The feral and pond nonspawning groups mainly differed in a signficantly higher concentration of 5 beta-pregnane-3 alpha,17 alpha-diol-20-one-glucuronide in the feral nonspawning fish. For the levels of etiocholanolone, testosterone, 5 beta-androstane-3 beta,17 beta-diol, and their glucuronides no significant differences were observed between the three groups, and 5 beta-dihydrotestosterone and its glucuronide could not be detected in the seminal vesicle fluid of any of the animals. The increase in the concentration of three 5 beta-reduced steroid glucuronides may point to a pheromonal function of one or more of these compounds, as demonstrated for the entire steroid glucuronide fraction of the seminal vesicle fluid. Experiments are being carried out to verify this hypothesis.     

The skin of the male African catfish, Clarias gariepinus: a source of steroid glucuronides

Steroid metabolism in the skin of mature male African catfish, Clarias gariepinus, reared in the laboratory, was studied in vitro by tissue incubations with [3H]pregnenolone, [3H]dehydroepiandrosterone, [3H]17 alpha-hydroxyprogesterone, [3H]androstenedione, [14C]11 beta-hydroxyandrostenedione, and [3H]testosterone as precursors. While pregnenolone was not converted to any other steroid, dehydroepiandrosterone was transformed mainly to 5-androstene-3 beta, 17 beta-diol. The products of 17 alpha-hydroxyprogesterone incubations were 5 beta-pregnane-3 alpha,17 alpha-diol-20-one, 5 beta-pregnane-3 alpha,17 alpha, 20 beta-triol, and 5 beta-pregnan-17 alpha-o1-3,20-dione. The major steroids of androstenedione incubations were etiocholanolone, testosterone, and androsterone. Testosterone was converted mainly to etiocholanolone and androstenedione, and only small quantities of 11 beta-hydroxytestosterone, 11-ketotestosterone, and 11-ketoandrostenedione were the metabolites found in 11 beta-hydroxyandrostenedione incubation. These results demonstrated the presence of the enzymes 5 alpha- and 5 beta-reductases and 3 alpha-, 11 beta-, 17 beta-, and 20 beta-hydroxysteroid dehydrogenases in the skin. From enzymehistochemical results it appeared that the steroid conversions take place in the epithelial cells. Moreover, the presence of UDP-glucose dehydrogenase, an enzyme involved in the synthesis of glucuronic acid, in these cells indicates the possibility of steroid glucuronide formation. Indeed significant amounts of water-soluble steroid conjugates, particularly 5 beta-dihydrotestosterone- and testosterone-glucuronide, were found in the incubations with androstenedione and testosterone, indicating the presence of the UDP-glucuronosyl transferase in the catfish skin. In the light of these results, a role of the skin of African catfish in the production of semiochemicals having pheromonal properties is discussed.     

In vitro biosynthesis of 17 alpha,20 alpha,20 beta-dihydroxy-4-pegnen-3-one by the ovaries, testes, and head kidneys of the Atlantic salmon Salmo salar

Ovaries, testes, and head kidneys of sexually mature Atlantic salmon, Salmo salar, biosynthesized 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOHP) from equimolar amounts of [3H]pregnenolone plus [4-14C]progesterone in vitro. The 3H:14C isotope ratios of steroid metabolites indicated that the biosynthetic pathways to 17 alpha,20 beta-diOHP in the testes differed from those observed in the ovaries and head kidneys. [4-14C]Progesterone appeared to be the principal precursor of 17 alpha,20 beta-diOHP in the testes, whereas both precursors were efficiently biotransformed to 17 alpha,20 beta-diOPH in the ovaries and head kidneys. 17 alpha-Hydroxy-4-pregnen-3-one (17 alpha-OHP) was the immediate precursor to 17 alpha,20 beta-diOHP in all tissues. However, appreciable amounts of 17 alpha,20 beta-diOHP accumulated in vitro in the testes only in the presence of exogenous [14C]progesterone. Incubation of the testes, ovaries, and head kidneys with [14C]pregnenolone resulted in high yields of 17 alpha,20 beta-diOHP in the ovaries and head kidneys but no detectable amounts of the steroid in the testes. The results confirm that progesterone is the favored precursor to 17 alpha,20 beta-diOHP in the testes. The results also suggest that the head kidneys may be an excellent cellular source of 17 alpha,20 beta-diOHP in both male and female. Atlantic salmon and may play an important role in the sexual maturation process in this fish. It is suggested that biosynthetic control mechanism affecting 17 alpha,20 beta-diOHP synthesis and/or spermiation and ovulation may differ in male and female Atlantic salmon.     

Histology, ultrastructure, and in vitro steroidogenesis of the testes of two male phenotypes of the protogynous fish, Thalassoma duperrey (Labridae)

Species with multiple male reproductive phenotypes may serve as model systems to study the relationship between form and function in reproduction. Large and small males of the protogynous wrasse, Thalassoma duperrey differ in reproductive behavior, gonad morphology, and gonadal steroid production. Initial-phase (IP) males are small males that spawn in groups. They have large testes with high sperm production. Terminal-phase (TP) males are large, defend temporary spawning territories, and spawn individually with females. TP males are derived from either IP males or from sex-changed females. Regardless of origin, TP males have much smaller testes than do IP males, but steroid-producing Leydig cells in the gonads of TP males appear more numerous and better developed. Testes of TP males produce more testosterone (T) and especially 11-ketotestosterone (11-KT) in vitro than do testes of IP males, and the production is more responsive to salmon gonadotropin. 11-KT was the major metabolite produced by incubating the gonads of TP males with 14C-labeled steroid precursors. In vitro 11-KT production was correlated with plasma levels of 11-KT in TP males and these levels were significantly higher than those of IP males. The in vitro conversion of 17 alpha-hydroxyprogesterone to 17 alpha, 20 beta-progestogen (17 alpha, 20 beta-P) for both types of males was similar, and was highest in winter when spawning occurred every day. Basal production of 17 alpha, 20 beta-P was similar in IP and TP male testes, and was enhanced by gonadotropin. The enzyme 20 beta-hydroxysteroid dehydrogenase, responsible for the conversion of 17 alpha-hydroxyprogesterone to 17 alpha, 20 beta-P resided in the sperm. These results indicate a function of 17 alpha, 20 beta-P in male reproductive function, probably spermiation, and a relationship of Leydig cell development and high levels of 11-KT production to the terminal male phenotype, perhaps reproductive or aggressive behavior, rather than to male gametogenesis per se.     

Endocrine changes during gonadal maturation and spawning in the orange roughy (Hoplostethus atlanticus Collett), a teleost from the midslope waters off New Zealand

Orange roughy were sampled at all stages of the reproductive cycle by trawling at depths of 700-1200 m off the coast of New Zealand. Blood samples were collected from live fish, and changes in plasma levels of gonadal steroids were correlated with gonadal development and spawning. Plasma androgens were low in spent and regressed fish of both sexes and increased during gametogenesis to peak early in the spawning period at 6.6 and 9.4 ng.ml-1 for males and females, respectively. Androgen levels dropped to near basal levels over successive days during the first week of spawning in both prespawning and ovulated or spermiated fish. Falls in plasma androgens were not accompanied by increasing levels of plasma 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta P) which remained at or near assay detection limits throughout. 11-Deoxycortisol (11-DOC) was present in the plasma of both sexes but did not change in concert with reproductive development. 17 beta-Estradiol was present in low concentrations (maximum 0.9 ng.ml-1 plasma) in recrudescing females, whereas estrone was detectable but not elevated at any stage. 17 alpha-Hydroxyprogesterone was not detectable in the plasma of any fish at any time. It is suggested that neither 17 alpha,20 beta P nor 11-DOC were active as maturation-inducing steroids (MIS) in orange roughy and that androgens may act as MIS. If the recorded fall in androgens was due to synthesis of another steroid from a common precursor, then the unidentified steroid does not appear to have been involved in stimulating final gamete maturation, but may have some action in initiating spawning behavior.     

Steroid metabolism in the testes of the breeding and nonbreeding three-spined stickleback, Gasterosteus aculeatus

Steroid metabolism in the testes of sticklebacks was studied in vitro by tissue incubations with [3H]pregnenolone or [3H]androstenedione as precursors. In males in full reproductive condition (nesting), [3H]pregnenolone was mainly converted via progesterone and 17 alpha-hydroxyprogesterone into androstenedione, 11 beta-hydroxyandrostenedione, and 11-ketoandrostenedione. The latter was the largest product formed. The main products from the [3H]androstenedione incubation, 11 beta-hydroxyandrostenedione and 11-ketoandrostenedione, confirm these findings. The rate of androgen synthesis, especially of 11-ketoandrostenedione, was much lower after the end of the breeding season.     

Effect of LH injections on testicular steroidogenesis, cholesterol side-chain cleavage P450 mRNA content and Leydig cell morphology in hypogonadal mice

Hypogonadal (hpg) mice have a congenital deficiency of hypothalamic gonadotrophin-releasing hormone (GnRH) and the gonads consequently lack exposure to gonadotrophins during development. We injected male hpg mice with LH for 10 days to investigate whether LH alone can stimulate normal steroidogenesis in these animals. Control animals had an inactive interstitium and very few germ cells. Testicular content of androgens was undetectable by radioimmunoassay in control animals unless a single injection of LH was given 1 h before death, when androgens were just detectable. Control testes incubated in vitro with [3H]pregnenolone demonstrated that without gonadotrophin stimulation pregnenolone was metabolized only to progesterone in significant amounts. Assay for cholesterol side-chain cleavage cytochrome P450 (P450scc) mRNA showed basal expression in saline-treated hpg mouse testis. LH treatment induced hypertrophy and hyperplasia of Leydig cells and division of germ cells. Testicular androgen content increased significantly, with testosterone and androstenedione as the major androgens. LH-treated testes incubated with [3H]pregnenolone in vitro had a greater synthetic capacity for testosterone, suggesting an increase in 17 alpha-hydroxylase/C17-20-lyase activity. Basal and human chorionic gonadotrophin-stimulated androgen production in vitro increased markedly following LH treatment to levels previously described in the normal adult animal. LH treatment caused a rapid and transient increase in the hybridization of P450scc mRNA which was sevenfold greater than that of saline-treated controls when the animals were killed 1 h after the last injection but fell to control levels within 24 h of cessation of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)     

Testicular steroidogenesis in the testicular feminized (Tfm) mouse: loss of 17 alpha-hydroxylase activity.

Testicular feminized (Tfm) mice are totally insensitive to androgen and may be used to study the role of the androgen receptor in normal development and function. We have examined testicular and Leydig cell steroidogenesis in Tfm mice. Serum bioactive LH was high in Tfm mice but serum testosterone was low and this was associated with a severe reduction in testicular testosterone production in vitro. Examination of [3H]pregnenolone metabolism by testes of Tfm mice indicated that progesterone, rather than testosterone, was the major steroid produced. Leydig cells were isolated from normal and Tfm mice and from normal mice in which testicular descent was surgically prevented before puberty. As in whole testes, androgen production in response to human chorionic gonadotrophin was severely reduced in Leydig cells from testes of Tfm mice compared with normal or cryptorchid groups. In contrast, progesterone production by Leydig cells from testes of Tfm mice was markedly increased in comparison with other groups. Total steroid production (progesterone plus androstenedione plus testosterone), however, was only 24% of normal in Leydig cells from Tfm mice. The pattern of steroid production by Leydig cells from cryptorchid testes was similar to control, although total steroid production was reduced to about 50% (this was significantly higher than the Tfm group, P less than 0.05). The high progesterone/androgen ratio in testes from Tfm mice suggested that 17 alpha-hydroxylase was depleted in these animals. To confirm this, activity of the four major steroidogenic enzymes associated with the smooth endoplasmic reticulum was measured.(ABSTRACT TRUNCATED AT 250 WORDS)     

The influence of mammalian and avian gonadotropins on in vitro ovarian steroid synthesis in the turtle (Chrysemys picta).

The synthesis of steroids from 7α[³H]cholesterol and 7α[³H]pregnenolone by turtle ovarian tissues in vitro was studied. Pregnenolone, 17α-hydroxypregnenolone, progesterone, 17α-hydroxyprogesterone, androstenedione, testosterone, dehydroepiandrosterone, estrone, estradiol 17β, estriol, and 16-epiestriol were identified as products. All estrogens were detectable in incubates of preovulatory follicular tissue, but only small quantities of estrone were found in incubates of follicular tissue from postovulatory animals and luteal tissue. The effects of mammalian and avian gonadotropins on the metabolism of tritiated precursors were studied. Both mammalian and avian LH were stimulatory when conversion of cholesterol or pregnenolone to major steroid products was examined. In particular, enhancement of estrogen biosynthesis predominated in preovulatory follicular tissue, whereas increased progestin yield was the major effect in follicular and luteal tissue from postovulatory animals. The effects of FSH were minimal compared to the same dose of LH. Thus, a slight increase in estrogen yield was only noted when preovulatory follicular tissue was incubated with cholesterol and mammalian FSH, and neither mammalian nor avian FSH had an effect on pregnenolone conversion by follicles from postovulatory animals. Prolactin had no effect on luteal progesterone synthesis when used alone, but reduced the stimulatory effect of mammalian LH on progesterone synthesis. 11-Desoxycorticosterone was not found to be a product of the turtle ovary under normal conditions or after in vitro ACTH stimulation.     

5 beta-pregnane-3 alpha,6 alpha,17 alpha,20 beta-tetrol and 5 beta-pregnane-3 alpha,6 alpha,17 alpha-triol-20-one: steroids of ovarian origin in the African catfish, Clarias gariepinus, during oocyte maturation

At the stage of oocyte maturation, three very polar steroids were demonstrated by in vitro incubations with tritiated pregnenolone in the ovaries of the African catfish, Clarias gariepinus. Two of these compounds could be identified by chromatography, derivatization, and oxidation as 5 beta-pregnane-3 alpha,6 alpha,17 alpha,20 beta-tetrol and 5 beta-pregnane-3 alpha,6 alpha,-17 alpha-triol-20-one. Blood plasma analysis by means of gas chromatography followed by mass spectrometry confirmed the presence of these steroids with selected ion monitoring. The occurrence of the five most characteristic ions of each steroid was demonstrated at the proper retention times and with the correct abundance ratios. These very polar steroids, which were identified in vitro and in vivo, might have a function in maturation and ovulation induction.     

Lack of essential enzymes for the biosynthesis of C19 and C18 steroids in gonads of the migratory locust, Locusta migratoria.

Ovaries and testes of the African migratory locust, Locusta migratoria migratorioides, were incubated in vitro with six tritiated steroid precursors. Three developmental stages were investigated--1 day, 14 days, and 6 weeks after adult moulting. 20 alpha-Hydroxysteroid dehydrogenase (HSD), 20 beta-HSD, 17 beta-HSD, 3 beta-HSD/isomerase, C17-C20 lyase, glucuronyl-transferase, sulfotransferase, and acyltransferase were identified in both sexes. A synthesis of androgens or estrogens comparable to the vertebrate type, however, was not apparent in the locust gonads. 20 alpha-HSD, 20 beta-HSD, and 17 beta-HSD activities were high, while more important steps in steroid synthesis such as 3 beta-HSD and C17-C20 lyase were far less intense. Ovarian 17 alpha-hydroxylase activity was slight. Aromatase activity was not demonstrated. Water-soluble conjugate formation was high in the incubations of "14th-day" and "6th-week" gonads but was absent in "1st-day" ovaries and testes. Active ester formation of pregnenolone was demonstrated in "6th-week" testes. The other steroid conversions were similar in all developmental stages investigated. Major differences between testes and ovaries were not observed. The gonads of the migratory locust are concluded not to produce androgens or estrogens.     

Gas chromatographic-mass spectrometric analysis of steroids and steroid glucuronides in the seminal vesicle fluid of the African catfish, Clarias gariepinus

Gas chromatographic-mass spectrometric analysis was carried out to identify steroids and steroid glucuronides in the seminal vesicle fluid of African catfish, Clarias gariepinus, collected in the Hula nature reserve (Israel) during the breeding season. Full mass spectra of 5 beta-pregnane-3 alpha, 17 alpha-diol-20-one and cholesterol were obtained. After treatment with beta-glucuronidase the following steroid glucuronides were determined by full mass spectra of the corresponding free steroids: etiocholanolone, 5 beta-androstane-3 alpha, 17 beta-diol-11-one, 5 beta-pregnane-3 alpha, 17 alpha-diol-20-one, and cholesterol. Furthermore, after selected ion monitoring the following steroids and steroid glucuronides could be detected by the presence of at least two characteristic ions at the expected retention time: 5 beta-androstane-3 beta, 17 beta-diol, 5 beta-androstane-3 alpha, 17 beta-diol, etiocholanolone, 5 beta-androstane-3 alpha, 17 beta-diol-11-one, testosterone, 5 beta-androstane-3 alpha, 17 beta-diol-glucuronide, and testosterone-glucuronide. These results agree with the hypothesis that steroid glucuronides, synthesized by the seminal vesicles, are excreted with the seminal vesicle fluid into the external environment, where they might function as sex pheromones.     

Follicle-stimulating hormone stimulates estradiol-17beta synthesis in cultured Sertoli cells.

Sertoli cells isolated from testes of 20-day-old rats and maintained in primary culture synthesized estradiol-17beta [1,3,5(10)-estratriene-3,17beta-diol] (measured by specific radioimmunoassay) when testosterone (17beta-hydroxy-4-androsten-3-one) 0.5 muM, was added to the culture medium. No detectable estradiol synthesis occurred when cells were incubated in medium containing pregnenolone (3beta-hydroxypregn-5-en-20-one), 0.5 muM, or containing no added steroid substrate. Follicle-stimulating hormone (FSH) (NIH-FSH-S10, 5 mug/ml) stimulated estradiol synthesis 12- to 80-fold when added to medium containing testosterone, but not when added to medium containing pregnenolone or no exogenous steroid substrate. A highly purified FSH preparation, with FSH potency 50 times that of the NIH-FSH, caused a similar stimulation at a concentration of 0.25 mug/ml of medium, whereas luteinizing hormone (NIH-LH-S18, 5 MUG/ML) Caused only marginal stimulation. Dibutyryl-adenosine 3':5' cyclic monophosphate, 0.1 mM, caused a 30-fold increase in estradiol synthesis by Sertoli cells cultured in medium containing testosterone. These studies provide direct demonstration of estradiol-17beta production by Seroli cells from normal animals, and offer evidence that the synthesis of this steroid is regulated at the level of the aromatizing enzyme system by FSH and adenosine 3':5' cyclic monophosphate.     

Steroid secretion of rainbow trout testis in vitro: variation during the reproductive cycle

Testicular tissue collected at different stages of gonadal development was incubated with a pituitary extract (PE) from mature salmon. Three androgens (11-ketotestosterone, OT; 11 beta-hydroxytestosterone, OHT; and testosterone, T) and 17 alpha,20 beta-dihydroxyprogesterone (17-20 beta P) were quantified by radioimmunoassay in incubation media. OHT and OT were secreted in larger quantities than T and 17-20 beta P. The PE dose that evoked a half-maximal response (ED50), the ratios of maximum stimulated vs baseline secretion, and total testicular steroid output all changed during the reproductive cycle. Androgen secretion in response to PE was low in immature and spent fish, both in terms of ED50 and the ratio of maximum stimulated vs baseline secretion. This ratio increased in testes showing the first signs of maturation and remained elevated during rapid testicular growth, before reaching maximum values at full maturity. The lowest ED50 values were found at the end of spermatogenesis and during the peak spawning period. 17-20 beta P secretion could not be stimulated noticeably until the fish had entered the spawning period and, as opposed to androgens, remained stimulable in spent fish. ED50 values for 17-20 beta P ranged, without showing clear-cut variations, above those calculated for androgens. The changes in PE reactivity and steroid secretion capacity during the reproductive cycle are likely to contribute to the changes in circulating steroid concentrations and may allow modulations of testicular steroid production without large changes in circulating GTH levels.     

Endocrine profiles in the males of a twice-annually spawning strain of rainbow trout, Salmo gairdneri

The male reproductive cycles of a twice-annually spawning strain of rainbow trout were studied by monitoring the plasma gonadotropin (GtH) and steroid hormone levels in individual fish for more than a year using thirty-five 2.5-year-old mature males. Twenty-five males survived the whole experimental period and were divided into four groups according to the amount of milt and endocrine profiles. In the summer breeding season, milt amount was negligible in Group I and small in Group II with low plasma testosterone, 11-ketotestosterone (11-KT), and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOH-P) levels, whereas both groups showed a large amount of milt and a distinct increase in steroid levels in the winter breeding season (November-January). Group III expelled a large amount of milt in both the summer and winter breeding seasons, and plasma testosterone, 11-KT, and 17 alpha,20 beta-diOH-P showed a clear peak in each breeding season. In Group IV, milt was expelled from December to July, and plasma steroid levels remained high until June before declining to the basal levels; however, these fish failed to mature in the ensuing winter breeding season. Plasma GtH levels in Groups III and IV were significantly higher than those in Groups I and II in the summer breeding season. These results clearly indicate that fish in Group III are twice-annual spawners.     

The effect of temperature on testicular steroid production in the rainbow trout, Salmo gairdneri, in vivo and in vitro

The effect of temperature on steroidogenesis in the male rainbow trout has been studied both in vitro using endogenous precursors under gonadotrophin stimulation and in vivo in fish held for 2 weeks at three different temperatures. In vitro, the optimum temperature for formation of testosterone and its 11-oxygenated derivatives was 10 degrees, whereas glucuronide formation showed an optimum at 18 degrees. In vivo, plasma levels of testosterone and 11-keto-testosterone were significantly higher at 6 than at 17 degrees, whereas glucuronide levels showed no significant difference. Milt was obtained only from fish held at 6 and 12 degrees. The optimum temperature for free steroid formation in response to gonadotrophin stimulus is shown to be dependent upon glucuronyl transferase content, and its progressive increase during the reproductive cycle may provide a mechanism for the inhibition of free steroid synthesis and hence spermiation at elevated temperatures where gamete survival is poor.     

Circannual and circadian variations in plasma levels of steroids (cortisol,estradiol-17β estrone,and testosterone) correlated with the annual gonadal cycle in the catfish, Heteropneustes fossilis (Bloch)

Circannual and circadian variations in plasma levels of steroids were estimated by radioimmunoassay in the female and male catfish, Heteropneustes fossilis, over two consecutive annual reproductive cycles. In the female catfish, testosterone (T), estradiol-17β (E₂), and estrone (E₁) were detectable in the plasma only during the reproductively active (preparatory through spawning) period and their levels increased during vitellogenesis. In the fully gravid catfish, when vitellogenesis was nearly complete, levels of E₂ declined but those of T continued to increase suggesting a product-precursor relationship between the two steroids. Plasma cortisol (F) was detectable throughout the year and exhibited three peaks coinciding with summer, monsoon, and winter; the first and second peaks coincided with vitellogenesis and spawning, respectively. In the male catfish, changes in plasma T and F levels closely paralleled the seasonal recrudescence and activity of testes and seminal vesicles. After spawning, gonads regressed and levels of sex steroids declined sharply. In the absence of natural spawning due to scanty monsoon rains, as during the second year of this study, gonadal regression was delayed and the sex steroids persisted in the plasma well beyond the normal spawning season. In addition, the first two peaks of F levels merged to form a plateau extending from the preparatory period until the late spawning period. The three sex steroids (T, E₂, and E₁) exhibited identical circadian rhythms; a major peak occurred at the onset of the dark phase (20:00 hr) and a minor peak was generally observed 4 hr after the onset of the light phase (12:00 hr). The amplitude of rhythms was greatest during the prespawning and the spawning periods. Cortisol peak levels generally alternated with those of sex steroids. Steroid rhythms show rather precise correlations with environmental factors such as photoperiod, temperature, and rainfall as well as with seasonal reproductive activity in both sexes of catfish.     

Ovine placental steroid 17 alpha-hydroxylase/C-17,20-lyase, aromatase and sulphatase in dexamethasone-induced and natural parturition

Parturition in the sheep is preceded by an abrupt alteration in placental steroid metabolism causing a shift from progesterone to oestrogen production. This change is believed to be a consequence of the preparatum rise in cortisol in the fetal circulation and involves increases in activities of the enzymes steroid 17 alpha-hydroxylase (cytochrome P-450(17) alpha), steroid C-17,20-lyase, and possibly aromatase and steroid sulphatase. The activity levels have been determined of steroid 17 alpha-hydroxylase, aromatase and steroid sulphatase in placental microsomes in late pregnancy, dexamethasone-induced labour and in natural labour at term. Over the gestational period of 118-140 days, basal levels of placental aromatase were relatively constant (mean value (+/- S.E.M.) of 5.6 +/- 0.5 pmol/min per mg microsomal protein (n = 10]. Pregnenolone and progesterone 17 alpha-hydroxylase activities were undetectable (less than 0.5 pmol/min per mg microsomal protein (n = 7]. In six animals in labour induced with infusion of dexamethasone into the fetus, placental aromatase activity increased to a value of 14.0 +/- 1.0 pmol/min per mg protein; placental pregnenolone 17 alpha-hydroxylase, measured in four of the animals, also increased to 453 +/- 77 pmol/min per mg microsomal protein. In five animals in natural spontaneous labour with vaginal delivery, aromatase activity was 26.7 +/- 5.2 pmol/min per mg microsomal protein and pregnenolone 17 alpha-hydroxylase activity was 141 +/- 14 pmol/min per mg microsomal protein. Steroid sulphatase activity was barely detectable (less than 1.5 pmol/min per mg microsomal protein) during late pregnancy, dexamethasone-induced labour or natural parturition.(ABSTRACT TRUNCATED AT 250 WORDS)