Oxidative side-chain and ring fission of pregnanes by Arthrobacter simplex.
(49/79)
Metabolic processes involving side-chain and ring cleavage of progesterone, 17-hydroxyprogesterone, 11-deoxycortisol and 16-dehydropregnenolone by Arthrobacter simplex were studied. The formation of the metabolites from progesterone indicates a pathway somewhat different from normal in the enzymic reaction sequence, and the 17-hydroxyprogesterone metabolites reveal a non-enzymic rearrangement step. The presence of a hydroxy group at C-21, as in 11-deoxycortisol, induces reduction of the C-20 carbonyl group. The microbial preparation of a novel androstane analogue, 17 beta-hydroxy-16 alpha-methoxyandrosta-1,4-dien-3-one, by incubation of 16-dehydropregnenolone with the bacterial strain was achieved. The formation of this metabolite is a multistep process involving a novel microbial generation of a methoxy group from a double-bond transformation in a steroid skeleton. (+info)
Calcium dependence of glucocorticoid-induced lymphocytolysis.
(50/79)
A potent glucocorticoid, triamcinolone acetonide (9alpha-fluoro-11beta, 16alpha,17alpha, 21-tetrahydroxypregna-1,4-diene-3,20-dione-16,17-acetonide) and a divalent cation ionophore (A23187) had similar effects in vitro on [3H]uridine uptake and on lysis of thymocytes of adrenalectomized rats. Removal of Ca2+ from the medium blunted the cytolytic action of triamcinolone acetonide and virtually eliminated that of A23187. In Ca2+-free media, treatment of the thymocytes for 15 hr with triamcinolone acetonide or A23187 followed by re-introduction of Ca2+ resulted in a rapid decrease in cell survival. Based on the time courses of the responses, triamcinolone acetonide and A23187 evoked proportionate increases in 45Ca uptake and lysis of the thymocytes. These findings implicate enhanced Ca2+ uptake in glucocorticoid-dependent lymphocytolysis. (+info)
Glucocorticoids increase insulin binding and the amount of insulin-receptor mRNA in human cultured lymphocytes.
(51/79)
The effect of steroid hormones on insulin binding and the amount of insulin-receptor mRNA was examined in IM-9 lymphocytes. Cortisol and cortexolone, but not oestrogen, increased both the binding of insulin and the amount of insulin-receptor mRNA in a time- and dose-dependent manner. Cortisol was most potent, and induced a 2-fold increase in insulin binding and a 4-fold increase in mRNA. The elevation in binding was due to an increased number of insulin receptors at the cell surface. The increase in mRNA involved all four of the insulin-receptor mRNAs and could not be inhibited by cycloheximide. The cortisol-induced increase in mRNA was associated with a 3-4-fold increase in the synthesis of pro-receptor. The relative potency of the three steroids indicated that these effects were mediated by an interaction with the glucocorticoid receptor. The results of this study suggest that cortisol can increase the number of insulin receptors at the cell surface by increasing the amounts of insulin-receptor mRNA and the synthesis de novo of insulin receptors. (+info)
Steroid inhibition of calcitriol-induced prolactin production in GH4C1 cells. Specificity and sensitivity.
(52/79)
The induction of prolactin (PRL)-gene expression by calcitriol (1,25-dihydroxyvitamin D3, 1,25-dihydroxycholecalciferol) in clonal rat pituitary tumour (GH4C1) cells was selectively inhibited by cortisol [IC50 (concentration causing 50% inhibition) = 3.2-4.1 nM]. The steroid specificity of this effect was investigated and various steroids were found to inhibit calcitriol-stimulated PRL production with the following relative potencies: cortisol, 1; dexamethasone, 8; 11-deoxycortisol, 0.5; corticosterone, 0.4; aldosterone, 0.07; testosterone and oestradiol, less than 0.003. The steroid antagonist RU 38486 did not affect basal or calcitriol-stimulated PRL production, but antagonized the effect of 10 nM-cortisol in a concentration-dependent manner. Neither progesterone nor 11-deoxycortisol antagonized the effect of 10 nM-cortisol. Calcitriol-induced PRL production was 14 times more sensitive to dexamethasone inhibition than was non-stimulated PRL production. Growth-hormone production was stimulated by dexamethasone, in the presence or absence of calcitriol, with a concentration-dependence similar to that of dexamethasone inhibition of basal PRL production. These data indicate that steroid inhibition of calcitriol-stimulated PRL production is a specific glucocorticoid effect. The sensitivity of calcitriol-stimulated PRL production to dexamethasone was 14-26-fold greater than that of other measured responses in the same cells. Two of the possible explanations for this selectively increased sensitivity to glucocorticoids are: amplification of the glucocorticoid effect via an induced mediator; and the presence of very-high-affinity glucocorticoid-receptor-binding sites on DNA. (+info)
Cefoxitin interferes with the "Clini-Skreen" column method for urinary 17-hydroxycorticosteroids.
(53/79)
Cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids. The apparent concentration of hormone is increased from three- to 10-fold in samples from patients receiving cefoxitin when the Amberlite XAD-2 "Clini-Skreen" column is used. To determine the mechanism of interference, we reacted aqueous solutions of cefoxitin, cortisol, cortisone, and 11-deoxycortisol with phenylhydrazine; recorded the adsorption spectra; and determined the molar absorptivities and the equilibrium and rate constants. Also, we recorded the absorption spectra of phenylhydrazine with eight other cepha antibiotics and benzylpenicillin. Cortisol, cortisone, 11-deoxycortisol, and cefoxitin react with phenylhydrazine and absorb light with superimposable spectra and absorption maxima of 410 nm. The other antibiotics react with phenylhydrazine but absorbance maxima of the products vary, none being at 410 nm. Cortisol, cortisone, and 11-deoxycortisol react with phenylhydrazine 35-fold faster, have equilibrium constants ninefold greater, and have molar absorptivities 1.6 times that of cefoxitin. Thus, cefoxitin interferes with determination of urinary 17-hydroxycorticosteroids by forming a chromophore with the same absorbance maximum and with a molar absorptivity similar to cortisol, but much more slowly. (+info)
Differential protein synthesis in steroid-treated ocular surface epithelium.
(54/79)
Topical prednisolone and cortexolone, a known glucocorticoid receptor antagonist, differentially affected the synthesis of proteins in normal corneal epithelium and migrating conjunctival epithelium after complete corneal deepithelialization, as measured by 35S-methionine incorporation and SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel) electrophoresis. Application of either prednisolone or cortexolone to corneal epithelium resulted in similar protein synthesis patterns, each showing two new protein bands of about 15K and 32K. Cortexolone, but not prednisolone, initiated the appearance of several protein bands of different molecular weights in the migrating conjunctival epithelium, while treatment with prednisolone plus cortexolone resulted in a pattern of protein bands which resembled the saline-treated control. Crude extracts of prednisolone-treated migrating epithelium also enhanced the inhibition of phospholipase A2 activity, and this prednisolone-induced inhibition was reversed by cortexolone. (+info)
Analysis of glucose levels during glucocorticoid-induced cataract formation in chick embryos.
(55/79)
When 15-day-old developing chick embryos were administered hydrocortisone hemisuccinate sodium (HC; 0.25 mumol/egg), the content of glucose in the lens markedly increased from around 6 hr, and reached about 25-30-fold above the matched control at 24-48 hr. Thereafter, the glucose level declined and returned to the control level by 100 hr. The profile of lenticular glucose levels was similar to that of the appearance and disappearance of lens opacification. Prednisolone, as well as HC, produced cataract and the elevation of glucose in the lenses. Cortexolone and cortisone, which have weak or negligible glucocorticoid activity in developing chick embryo, could neither produce cataract nor the elevation of glucose in the lenses. An attempt was made to find similarity between this glucocorticoid-induced cataract and sugar cataract known in mammals. In both control and HC-induced cataract (stage IV-V) obtained 48 hr after HC administration, sorbitol, fructose, and glycosylation of protein could not be detected. Dehydration was observed in HC-induced cataractous lens. These data demonstrate that the glycosylation of lenticular protein and the accumulation of polyol were not involved in glucocorticoid-induced cataract formation in developing chick embryos. These results suggest a relationship between the elevation of glucose and cataract formation. However, when cataract formation was blocked by ascorbic acid treatment, the glucose level remained high. Therefore, any relationship between glucose level and cataract may be complex or indirect. (+info)
Acute stimulation by glucocorticoids of gluconeogenesis from lactate/pyruvate in isolated hepatocytes from normal and adrenalectomized rats.
(56/79)
Dexamethasone stimulated gluconeogenesis from lactate/pyruvate in suspensions of hepatocytes isolated from both adrenalectomized and normal fasted rats. This stimulation was observed in incubations with 1 mM pyruvate and at a lactate/pyruvate ratio of 25 but not at a ratio of 10-13. At a lactate/pyruvate ratio of 10-13, the stimulation by dexamethasone was progressively enhanced as the pyruvate concentration was decreased to 0.25 mM. Concurrent administration of a maximally stimulating concentration of dexamethasone with angiotensin II or glucagon yielded an additive stimulation at all concentrations of the peptide hormones tested. No potentiating or permissive actions of acute glucocorticoid administration were observed using hepatocytes from either normal or adrenalectomized animals. The acute stimulation by dexamethasone was antagonized by prior addition of progesterone or cortexolone to the hepatocyte suspensions. Triamcinolone and corticosterone also stimulated gluconeogenesis. Concentrations of the active glucocorticoids needed to elicit half-maximal stimulations (Kact) were approximately 100 nM for dexamethasone and triamcinolone and 400 nM for corticosterone. Deoxycorticosterone, 17 alpha-methyltestosterone, and 5 beta-dihydrocortisol did not stimulate. Stimulation of gluconeogenesis by dexamethasone was seen following a lag averaging 9 min after the time of steroid addition. Preliminary evidence suggests that this effect was not dependent upon a stimulation of protein synthesis, but the observed stimulation and inhibition of control rates of gluconeogenesis by cycloheximide and cordycepin, respectively, demonstrate the difficulties of working with such inhibitors in attempting to answer this question. (+info)