Showing papers on "Steroid biosynthesis published in 1969"

Differentiation of interstitial cells and sertoli cells in fetal guinea pig testes

Abstract: Smooth endoplasmic reticulum appears in interstitial cells and Sertoli cells of 22–24d testes of fetal guinea pigs before the beginning of morphological differentiation of the male reproductive tract at 29d (Price et al., '67), and before the appearance of demonstrable 3β-hydroxysteroid dehydrogenase, an enzyme important in steroid biosynthesis, in the interstitial cells at 29d (Ortiz et al., '66). This enzyme has not yet been demonstrated in the Sertoli cells. The smooth reticulum of the interstitial cells increases in amount, filling the cells with tubules by 27d, and later forming some fenestrated cisternae which are occasionally seen in whorls. In Sertoli cells, the tubular reticulum shows signs of degeneration at 26d. After this time the cisternal endoplasmic reticulum in these cells increases in amount and by 45d is predominantly smooth-surfaced. Yet it is never as prominent as the smooth reticulum of the interstitial cells. Scattered clusters of ribosomes or polyribosomes are seen on the surface of the tubular reticulum of these differentiating cells. These polyribosomes become more widely spaced as the smooth-surfaced areas increase and may be associated with the production of smooth membranes. Smooth endoplasmic reticulum is known to play a role in the production of steroid hormones, and therefore the extensive development of smooth reticulum in fetal interstitial cells is consistent with experimental evidence that implicates these cells as the chief source of steroid hormones governing male reproductive tract differentiation.

Steroid Biosynthesis by the Equine Testis

Abstract: Enzyme reactions in the stallion testis involved in steroid synthesis were studied to determine the factors which account for the high production of estrogens as well as androgens. In comparison with other species, the stallion testis was found to have lower 17β- (testosterone) dehydrogenase activity and very high 19-(androstenedione) hydroxylase and aromatizing systems. As a consequence, while androstenedione served as a precursor of both testosterone and estrone, a greater proportion was converted to the estrogen. The 19-hydroxylation and aromatizing activities for testosterone seemed lower than those for androstenedione. The 3β-hydroxysteroid dehydrogenase systems for 17-hydroxypregnenolone and dehydroepiandrosterone were very active, but the A6-17,20- lyase system was apparently much less active than the A4-17,20-lyase. The predominant route of biosynthesis seems, therefore, to be: pregnenolone →17-hydroxypregnenolone →17-hydroxyprogesterone →Δ4-androstenedione →19-hydroxy- ↓androstenedione→estrone te...

Adrenal cells in tissue culture. IV. Use of an inhibitor of steroid synthesis for the study of ACTH action.

Abstract: This report describes the use of aminoglutethimide (AG), an inhibitor of steroid synthesis, for the study of some effects of ACTH on the metabolism of functional monolayer cultures of murine adrenal cortex tumors. At concentrations in the medium of 10 μg/ml or higher, the drug specifically blocks steroid biosynthesis from cholesterol. At concentrations over 50 μg/ml it is also a competitive inhibitor of 11β-hydroxylation. Its action is immediate and reversible. Concentrations in excess of 100 μg/ml have no adverse effect on cell growth, RNA and protein synthesis, glycolysis or cholesterol synthesis. Four effects of ACTH which we have previously described were investigated: the steroidogenic response to ACTH, the augmentation of steroidogenesis by prolonged stimulation with ACTH, the increased synthesis of cholesterol from acetate, and the stimulation of glycolytic activity. At concentrations over 10 μg/ml, both control and stimulated steroidogenic activity is blocked. At lower concentrations, the ratio of...

The role of a cholesta-8,14-dien-3β-ol system in cholesterol biosynthesis

Abstract: The biosynthesis of cholesterol from squalene and tritiated water is described. Degradation of the cholesterol indicated that C-15 may be involved in cholesterol biosynthesis. In accordance with this view it is shown that in the conversion of [2RS-(3)H(2)]mevalonic acid into cholesterol one of the hydrogen atoms at C-15 is removed. A mechanism for the removal of the 14alpha-methyl group in steroid biosynthesis that involves the labilization of a C-15 hydrogen atom is outlined. In accordance with the requirement of this scheme it is shown that 4,4'-dimethyl-cholesta-8,14-dien-3beta-ol is converted into cholesterol.

Persistence of the Steroidogenic Effect of Adenosine-3′,5′- Monophosphate in Vitro: Evidence for a Third Factor During the Steroidogenic Effect of ACTH

Abstract: When added simultaneously with CAMP (adenosine-3′,5′-monophosphate), inhibitors of protein synthesis block the steroidogenic effect of CAMP in rat adrenal sections in vitro. However, after prior stimulation of adrenal sections by CAMP for 10–30 min, heightened rates of steroidogenesis persist despite removing CAMP from the medium and/or adding cycloheximide or chloramphenicol. This previously established steroidogenic effect continues undiminished for 30–40 min, and then decays with a half-life of about 25 min. Virtually identical results are obtained when ACTH is employed as the stimulator, and this is compatible with the hypothesis that CAMP is the intracellular mediator of ACTH action. Since aminoglutethimide, an inhibitor of cholesterol side chain cleavage, largely blocks the persistent steroidogenic effect of CAMP, the latter effect cannot be explained by an accumulation of steroid precursors beyond this important step in steroid biosynthesis. Thepresent findings indicate that the steroidogenic effec...

Ultrastructural zonation of the human adrenal cortex.

Abstract: Electron microscopic observations of sections from adrenal cortex obtained from a twenty-four-year-old male with hypertension were made. In the zona glomerulosa the cells showed a large nuclear-cytoplasmic ratio. The mitochondria had a dark matrix and plate-like inner structure. The agranular endoplasmic reticulum revealed a close association with lipid granules. The Golgi apparatus was prominent and frequently accompanied by centrioles. Free ribosomes were abundant. The zona fasciculata can be subdivided into two layers. In the outer layer the cells are characterized by numerous large lipid granules. Two kinds of mitochondria are discernible; one with a pale matrix and tubulo-vesicular or vesicular inner structure and the other with a dark matrix and tubulo-vesicular or lamelllform cristae. In the inner zona fasciculata and reticularis there are two types of cells besides the dark cells. The type 1 cells have a compact cytoplasm, elliptic or irregularly shaped mitochondria with a dark matrix and tubulo-vesicular or vesicular internal structure. The type 2 cells are large and ovoid, having a clear transparent cytoplasm. The mitochondria are numerous having a clear matrix and almost exclusively vesicular inner elements. Abundance in agranular endoplasmic reticulum, decreased lipid granules, and cytoplasmic incisions are common in both the inner fasciculata and reticularis. In addition the zona reticularis is characterized by increased number of dark cells, numerous pigment bodies, and the appearance of huge mitochondria. On the basis of these observation were discussed the significance of the organelles in steroid biosynthesis, mode of hormone secretion, and cyto-genesls in the adrenal cortex.

I – Biochemical Studies

Abstract: In the testes of strains of mice which have a high incidence of Leydig cell tumors after continuous estrogen treatment for 7-12 months the estrogens produce a measurable reduction in the activities of three types of enzymes involved in steroid biosynthesis. This reduction takes place within the first 24-48 hours, By the end of 2 weeks the activities are reduced to 5-15 % of those of the untreated controls. This low level continues throughout the period of tumor induction. The effect can be seen in hypophysectomized mice treated with a constant dose of gonadotropin; it is not, therefore, due to an action of estrogens on the hypophysis. Such a marked direct effect is not seen in rats or in strains of mice which do not develop such tumors. A number of other enzymes, including the 3s-hydroxysteroid dehydrogenases, are not decreased when the influence on the three types of enzyme is maximal. The reduction is not due to direct inhibition by either the estrogens or their metabolic products, but to a decrease in the concentration of active enzyme molecules. If high specific activity diethylstilbestrol (DES)−3 H is used to treat cryptorchid male mice for 2 weeks, the highest concentration is in the nuclear fraction rather than in the microsomes. Much of this is in the lipoprotein nuclear membrane but considerable amounts remain associated with the chromatin after detergent treatment, lysis and trypsin digestion. If the trypsin-treated material is then fractionated by equilibrium centrifugation in a cesium chloride gradient the protein layer contains all radioactivity except a trace which remains with the DNA. The RNA fraction does not contain any radioactivity. Synthesis of DNA in cryptorchid testes of susceptible mice is increased within the first few hours after estrogen administration is begun. It reaches a peak on the third day and then recedes. Thereafter concentration of DNA remains higher in the testes of the treated mice than in paired controls. This is not true in rats or in a strain of mice which have a low tumor incidence. Radioautographs reveal that the spermatogonia of the tubules of the cryptorchid testes continue to undergo synchronous DNA synthesis and mitosis whether or not the mice are treated for as long as 7 months with DES. The interstitial cells, however, change from very low to marked DNA synthesis within the first 3 days. They then seem to follow either of two courses. In some regions they cease to synthesize DNA rapidly and begin to accumulate ceroid, while in others some incorporation continues. These regions apparently ultimately develop into nodules, some of which become malignant.

Aminoglutethimide (Elipten® CIBA)—A New Inhibitor of Steroid Biosynthesis

Abstract: Excerpt Aminoglutethimide (Elipten® CIBA) is derived from the nonbarbiturate hypnotic glutethimide (Doriden®) from which it differs only by the presence of an —NH2group. It has been used for severa...

Steroid Biosynthesis in a Feminizing Adrenal Carcinoma

Abstract: Minced tissue from a feminizing adrenal carcinoma was incubated for 1 hr with cofactors and equimolar amounts of 7α-3H-pregnenolone and 4-14C-progesterone. Seventeen compounds were isolated and recrystallized to constant specific activity. The isotopic ratios indicated that the conversion of pregnenolone to progesterone was negligible and that 3H in 17-hydroxyprogesterone came primarily by way of 17-hydroxypregnenolone. The 16-hydroxy derivatives of progesterone, testosterone and androstenedione were derived exclusively from 14C-progesterone, as were desoxycorticosterone, corticosterone, corticosterone, compound A and aldosterone. Pregnenolone gave rise to a high proportion of isotopically labeled 17-hydroxyprogesterone, testosterone, 2-hydroxytestosterone and estrone. The series 17-hydroxyprogesterone→compound S→cortisol→Reichstein's V showed a 3H/14C ratio which decreased successively: 12.2, 8.1, 6.5, 2.6. All these findings confirm the predominant role of pregnenolone as precursor for C19 and ...

Steroid Biosynthesis in Vitro by Transplantable Interstitial Cell Tumor of Mice. II. Metabolism of 11-Deoxycorticosterone and 11-Deoxycortisol

Abstract: The homogenate of the transplantable testicular tumor which originated in the interstitial cellsof mice (Endocrinology 83:659, 1968) was incubated with 14C-labeled 11-deoxycorticosterone and 11-deoxycortisol. As the metabolites of 11-deoxycorticosterone, radioactive 11-deoxycortisol, 18-hydroxy-11-deoxycorticosterone, corticosterone, aldosterone, 3α-tetrahydrocorticosterone, 5β-dihydro-11-deoxycorticosterone and 3α-tetrahydro-11-deoxycorticosterone were identified. On the other hand, from the radioactive 11-deoxycortisol, androstenedione, testosterone, 11β-hydroxyandrostenedione, cortisol, cortisone, 5β-dihydrocortisol, 3α-tetrahydrocortisol and α-cortol were derived by the homogenate of this tumor in vitro. These results suggest that the activities of the cortisol-C17-C20 lyase, 17α-hydroxylase which acts upon 11-deoxycorticosterone and converts it into 11-deoxycortisol, 11β-hydroxylaseand 11β-hydroxysteroid dehydrogenase, all of which could not be found in normal testicular tissue of mice, were present ...

Some Aspects of Steroid Transformations in the Testes of Human Subjects and of Rats with Experimental Cryptorchidism or Feminisation

Abstract: Summary The in vitro approach to the study of steroid biosynthesis yields information about the sequence of biochemical transformations which can occur in gonadal tissue and complements investigations in vivo. The current concept of steroid transformations in human testicular tissue is based upon studies performed under differing experimental conditions and the situation in healthy and pathological tissue is by no means established. In this short communication, representative results from two types of in vitro study will be described — experiments in which aliquots of the same tissue were incubated with the same isotopically labelled substrate for varying periods of time; and those in which the same tissue was incubated with several substrates for a constant time. In addition to a series of incubations of human testicular tissue, the rat testis was selected for comparative studies which could not have been performed in human subjects. The main feature of this work was the use of a variety of labelled steroid precursors in a series of replicate experiments which were performed under standardised conditions in three groups of rats-controls; experimental cryptorchidism; and after feminisation by the administration of the anti-androgen — Cyproterone — to the mother rats during pregnancy and to the newborn (as the acetate) during the first ten days of life. After extensive purification, evidence for the identity of the radiometabolites was obtained by gas-liquid chromatography and by recrystallisation to constant specific activity. The reproducibility of results obtained from replicate incubations permits general conclusions as to the extent of incorporation of radioactivity into the principal products and a tentative interpretation in terms of major enzymatic transformations. The results indicate an increase in 3β-ol-dehydrogenation, 17-hydroxylation and side-chain cleavage in the cryptorchid testes accompanied by a decrease in 17-ketosteroid reduction. On the other hand in the tests of the feminised animals there is evidence for impairment of both 17-hydroxylation and of the side-chain clearage of δ4-3-ketosteroid intermediaries. The results obtained in human and rat testes will be discussed with special reference to the capacity for the formation of testosterone and oestradiol-17β.