Showing papers on "Steroid biosynthesis published in 1990"

Establishment and characterization of a human adrenocortical carcinoma cell line that expresses multiple pathways of steroid biosynthesis

Abstract: We established a continuous cell line, NCI-H295, from an invasive primary adrenocortical carcinoma. The cell line was established in a fully defined medium (HITES) and later could be adapted for growth in a simple medium supplemented only with selenium, insulin, and transferrin and devoid of serum, steroids, fibroblast growth factor, and a source of exogenous cholesterol. NCI-H295 cells had a relatively long population doubling time and were tumorigenic when inoculated s.c. into athymic nude mice. The cultured cells had ultrastructural features of steroid-secreting cells and contained complex cytogenetic abnormalities including the presence of multiple marker chromosomes. Steroid analyses (radioimmunoassays and mass spectrometry), performed 7 to 9 years after culture initiation, demonstrated secretion of more than 30 steroids characteristic of adrenocortical cells. Total unconjugated steroid secretion in serum-supplemented medium was 2.83 micrograms/10(6) cells/24 h and about 4-fold less in serum-free medium. The major pathway of pregnenolone metabolism in NCI-H295 cells is androgen synthesis, with formation of dehydroepiandrosterone, androstenedione, testotesterone, and at least three sulfated androgens, as well as estrogens. In addition, formation of cortisol, corticosterone, aldosterone, and 11 beta-hydroxyandrostenidione indicated the presence of 11 beta-hydroxylase. Thus, multiple pathways of steroidogenesis are expressed by NCI-H295 cells, including formation of corticosteroids, mineralocorticoids, androgens, and estrogens. Our findings indicate the presence in NCI-H295 cells of all of the major adrenocortical enzyme systems, including 11 beta-hydroxylase, desmolase, 21 alpha-hydroxylase, 17 alpha-hydroxylase, 18-hydroxylase, lyase, sulfokinase, and aromatase. The NCI-H295 cell line should prove of value in studying the regulation, metabolic pathways, and enzymes involved in steroid formation and secretion. In addition, it may provide insights into the biology and treatment of adrenocortical carcinoma.

R 75251, a new inhibitor of steroid biosynthesis.

Abstract: R 75251, a new imidazole derivative, inhibited the conversion of androgens to estrogens, of progestins to androstenedione and testosterone, and of 11-deoxycorticosterone to corticosterone in human placenta microsomes, subcellular fraction of rat testis, bovine adrenocortical mitochondria, in cultured rat granulosa, testicular and adrenal cells, respectively. In vitro, no effect on cholesterol synthesis and cholesterol side-chain cleavage was found at concentrations up to 10 microM. In rat granulosa cells, no effect on progesterone production was detected. In vitro, no effect on steroid radioligand binding was observed. In male volunteers, a single dose of 300 mg of R 75251 significantly lowered plasma testosterone and estradiol for 24 hours and increased plasma concentration of 17 alpha-hydroxyprogesterone and progesterone. As compared with ketoconazole high dose (600 mg b.i.d), R 75251 (300 mg b.i.d) was at least as efficacious as inhibitor of testosterone synthesis when studied during ACTH stimulation. In contrast to ketoconazole, R 75251 did not significantly affect circulating adrenal androgen levels in male volunteers. Precursors of gluco- and mineralocorticoids such as 11-deoxycortisol and 11-deoxycorticosterone accumulated more than after ketoconazole administration. The data show that the cytochrome P450-dependent aromatase, 17-hydroxylase/17,20-lyase, and 11-hydroxylase are the target enzymes for R 75251.

Tumor inhibiting [1,2-bis(fluorophenyl)ethylenediamine]platinum(II) complexes, III: Evaluation of the mammary tumor inhibiting properties

Abstract: Diastereomeric diaqua[1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II) sulfates and nitrates produce a strong inhibition of the hormone-dependent MXT-M 3.2 mammary carcinoma of the B6D2F1 mouse. Besides an interference in the DNA synthesis in analogy to cisplatin a lowering of the estrogen level due to an interference in steroid biosynthesis is suggested as the mode of action. In contrast to the R,R/S,S configurated diaqua[1,2-bis(4-fluorophenyl)ethylenediamine]platinum(II) salts the corresponding R,S configurated compounds are also markedly active on the hormone-independent MXT-Ovex mammary carcinoma of the B6D2F1 mouse.

Animal growth promotion

Abstract: Female prenatal, neonatal and postnatal animals are treated with compositions containing steroid biosynthesis inhibitors or antagonists which prevents the conversion of androgens to estrogens. The compositions are useful for improving growth and feed efficiency.

Biochemistry and Molecular Biology of Insect Cytochrome P450

Abstract: Cytochrome P450 monooxygenases (P450) are a diverse and ubiquitous group of enzymes encoded by genes from a superfamily comprising at least 17 families, and probably many more (Nebert and Gonzalez, 1987; Nebert et al., 1989). Our present understanding of P450 enzymes comes mainly from studies of P450 in vertebrates, where they are involved in steroid biosynthesis and in the metabolism of drugs and chemical carcinogens, and in bacteria, with P450 cam from Pseudomonas putida being the only P450 enzyme for which a crystal structure is presently available (Poulos et al., 1987).

Neuroendocrinological effects of ketoconazole in rats.

Abstract: The effect of ketoconazole on steroid synthesis was studied in intact (sham-operated) and castrated male and ovariectomized female rats. Rats were given 25 mg/kg ketoconazole twice a day im for 5 days. The influence of ketoconazole was also investigated on hormone release altered by GnRH, estradiol and haloperidol. The following hormones were measured: serum LH, PRL, testosterone, corticosterone, 17-OH-progesterone, estradiol, and dopamine content of the tubero-infundibular area. Ketoconazole treatment resulted in a significant decrease of testerone level (from 7.93 +/- 1.99 to 3.83 +/- 0.94 nmol/l), whereas LH, PRL, corticosterone and 17-OH-progesterone remained unchanged in the male rat. The effect of castration on LH level was reduced by ketoconazole in male (from 590 +/- 35 to 390 +/- 25 micrograms/l) and female rats (from 468 +/- 22 to 346 +/- 39 micrograms/l), but the GnRH-stimulated LH release in castrated and ovariectomized animals was unchanged. The suppressive action of estradiol on LH in ovariectomized rats was enhanced (from 160 +/- 41 to 64.6 +/- 12.9 micrograms/l), and its priming effect on PRL release was diminished by ketoconazole (from 598 +/- 81 to 281 +/- 66 micrograms/l). Ketoconazole failed to modify the tubero-infundibular dopamine content and haloperidol-induced PRL release. It can be assumed that in addition to its inhibitory role of steroid biosynthesis ketoconazole has an influence on central mechanisms underlying LH and PRL release.

Use of aromatese inhibitors for the reversal of female sexual phenotype in poultry

Abstract: Fertilized poultry embryos are treated with steroid biosynthesis inhibitors or antagonists which prevents the conversion of androgens to estrogens. By blocking the production of estrogens the genotypic female is converted into a phenotypic male. The phenotypic conversion of females to males gives the treated birds the advantage of male growth characteristics. A single administration of a steroid biosynthesis inhibitor or antagonist prior to about day 9 of embryonic incubation results in an irreversible change the sexual phenotype.

Vertebrate-Type Neuropeptides and Steroids in Locusta migratoria: Identification and Metabolism

Abstract: The search for “vertebrate-type” steroid hormones in insects was initiated in our lab after Huybrechts and De Loof (1977, 1982) succeeded in inducing vitellogenin synthesis in male flies (Sarcophaga bullata, Calliphora erythrocephala, Musca domestica, Phormia regina) by injecting or feeding 20-hydroxyecdysone Flies apparently use this steroid as the equivalent of estrogens in vertebrates, which use this steroid for control of vitellogenin synthesis by the liver When the search for a male-specific ecdysteroid did not yield any positive result, the question was raised whether insects might perhaps have some typical “vertebrate-type” steroids There is now hard evidence that at least 10 different such steroids are indeed present in insects Not clear at all is whether these steroids derive either from food or from biosynthesis In a parallel line of research, the possible presence of molecules resembling the peptide hormones that control steroid biosynthesis in vertebrates (eg LH, FSH, ACTH) was investigated Immunocytochemical data suggest that they are indeed present None of these has as yet been isolated, however, but as an indirect result, a lot of other neuropeptides have been fully characterized