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PubMed1975

Inhibition of ACTH response to oral and intravenous metyrapone by antiserotoninergic treatment in man.

Plasma ACTH levels after oral and iv metyrapone administration were studied in 7 and 5 healthy women respectively both under basal conditions and after a 4-day treatment with metergoline, a specific antiserotoninergic agent. In 3 additional women, the effects of methysergide, another antiserotoninergic drug, on the plasma ACTH rise induced by oral metyrapone, were evaluated. A significant lowering of the plasma ACTH levels attained after either oral or iv metyrapone was observed following metergoline administration: 149+/-64.3 vs 239+/-49.1 pg/ml (mean peak values), P less than 0.05 in the oral test and 331+/-19.7 vs 221+/-19.5 pg/ml, P less than 0.02 in the iv test. The fall of plasma cortisol caused by metyrapone was comparable before and after the antiserotoninergic treatment. An interference of metergoline in the ACTH radioimmunoassay was also excluded. After metergoline administration, a slight reduction in the baseline plasma ACTH values was noted: 79+/-7.7 vs 67+/-7.7 pg/ml (NS). A decrease, however not statistically significant, of the metyrapone-induced plasma ACTH elevation occured after methysergide administration: 421+/-150.7 vs 344+/-135.1 pg/ml. These results can be interpreted as indicating that antiserotoninergic treatment caused an inhibition of hypophysial ACTH release in response to metyrapone. Caution is recommended, however, before concluding, on the basis of these findings, that serotonin as such plays a physiological stimulating role on ACTH secretion.

Administration, Oral↗
PubMed1990

Effect of metyrapone pretreatment on adrenocorticotropin secretion induced by corticotropin-releasing hormone in normal subjects and patients with Cushing's disease.

To examine the influence of endogenous cortisol on the ACTH response to CRH, we compared ACTH secretion during CRH tests before and after metyrapone administration in 9 normal subjects and 12 patients with Cushing's disease. The administration of 4.5 g metyrapone (750 mg, orally, every 4 h) resulted in a decrease in basal (pre-CRH) plasma cortisol levels and an increase in basal plasma ACTH levels in both normal subjects and Cushing's patients. The pretreatment with metyrapone significantly blunted the increase in plasma cortisol levels and markedly enhanced ACTH secretion after iv injection of 100 micrograms human CRH. The peak ACTH levels during CRH test before and after metyrapone administration were 8 +/- 1 and 58 +/- 8 pmol/L, respectively, in normal subjects (P less than 0.01) and 26 +/- 5 and 50 +/- 11 pmol/L, respectively, in Cushing's patients (P less than 0.05). Although the basal and peak ACTH levels as well as delta ACTH (peak ACTH - basal ACTH) during the CRH test before metyrapone administration were significantly higher in Cushing's disease patients than in normal subjects (P less than 0.01), no such difference was observed between the 2 groups after metyrapone administration. The results clearly indicate that the endogenous cortisol levels greatly influence the ACTH response to CRH, and that the CRH test as commonly performed does not allow a correct evaluation of potential responsiveness of normal pituitaries and Cushing's adenomas to CRH.

Adolescent↗
PubMedDate not supplied

Assessment of hypothalamic-pituitary-adrenocortical axis function in dexamethasone treated very low birth weight infants by a single dose metyrapone test and gas chromatographic mass spectrometric determination of urinary steroids.

In order to assess hypothalamic-pituitary-adrenocortical axis function, we conducted low and single oral dose metyrapone tests (35 mg/kg) in dexamethasone treated very low birth weight infants with bronchopulmonary dysplasia (n = 12). The responses to metyrapone of tetrahydro-11-deoxycortisol (THS) and cortisol metabolites were analyzed by gas chromatography and mass spectrometry in 24-h urinary specimens. For comparative reasons, morning plasma 11-deoxy-cortisol and cortisol were measured by radioimmunoassay before and after metyrapone. No side effects of metyrapone were observed in our patients. In 5 of 12 patients, no urinary THS could be stimulated after metyrapone and most of the other patients had small increases in urinary THS. These findings suggest suppressed or strongly impaired hypothalamic-pituitary-adrenocortical axis function in most patients. While the concentrations of plasma 11-deoxycortisol showed little variation, those of plasma cortisol were grossly different from the respective urinary values. We recommend steroid analysis in 24-h urinary specimens by gas chromatography and mass spectrometry, because urinary steroids provide more information and the highly specific analytical technique is independent of phenomena such as cross reactivity or matrix effects. The low and single oral dose metyrapone test in combination with urinary steroid analysis by gas chromatography and mass spectrometry therefore provides a noninvasive, convenient and safe means of evaluating the integrity of the hypothalamic-pituitary-adrenocortical axis in very low birth weight infants.

Adrenal Cortex↗
PubMed1985

Aminoglutethimide and metyrapone in the management of Cushing's syndrome.

Fifteen patients with endogenous Cushing's syndrome were treated with metyrapone and/or amino-glutethimide. The duration of the therapy varied from 19 up to 365 days. In patients with Cushing's disease, metyrapone (0.5-2.5 g/day) and aminoglutethimide (0.5-1.5 g/day) seemed equally effective in reducing the cortisol excretion (54 +/- 9 vs 40 +/- 7%). The majority of these patients also showed a clinical improvement. In 1 patient with adrenal adenoma, metyrapone induced a remission. In another patient with adrenocortical cancer, and in 2 with the ectopic ACTH syndrome, the cortisol excretion was significantly reduced by the combination of metyrapone and aminoglutethimide but no obvious clinical improvement was observed. Side effects i.e. rash and pruritus attributed to aminoglutethimide was seen in 3 patients which necessitated the omission of treatment in 2. On metyrapone a moderate hypertrichosis was observed in 1 patient. In conclusion both metyrapone and aminoglutethimide were useful as adjunctive therapy in Cushing's syndrome.

ACTH Syndrome, Ectopic↗
PubMedDate not supplied

Effects of metyrapone on hepatic cortisone-cortisol conversion in the rat.

In previous studies in human subjects metyrapone has been found to exert significant extra-adrenal effects, consistent with an effect on the 11-reductase activity of 11beta-hydroxysteroid dehydrogenase (11beta-HSD). In the present study the effects of metyrapone on cortisone metabolism by rat liver microsomes were investigated. Aliquots of microsomal preparations were incubated with NADPH cofactor and different concentrations of cortisone for a range of time intervals up to 30 min. The products of the reaction were extracted with ethyl acetate and separated using thin-layer chromatograph. Cortisol was estimated by radioimmunoassay. There was a linear increase in cortisol formation over the first 150 sec of the reaction. Over this time period metyrapone had no effect on the rate of the reaction. When the reaction was allowed to proceed for 30 min, however, metyrapone caused a 50% decrease in the amount of cortisol formed. These data suggest that metyrapone may alter cortisone-cortisol conversion by directly interacting with 11beta-HSD but in this system metyrapone does not appear to have the characteristics of a conventional enzyme inhibitor.

Animals↗
PubMedDate not supplied

Effect of metyrapone supplementation on imipramine therapy in patients with treatment-resistant unipolar depression.

The paper describes the effect of metyrapone supplementation on imipramine therapy in patients (with treatment-resistant unipolar depression) who fulfilled DSM IV criteria for major depression. Nine patients were enrolled to the study on the basis of history of their illness and therapy. Following 2 weeks of washout period, the patients were treated with imipramine twice daily (100 mg/day) for 6 weeks, and then metyrapone was introduced (twice daily, 500 mg/day), and administered jointly with imipramine for further 6 weeks. Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI) were used to assess efficacy of antidepressant therapy. Imipramine changed neither HDRS nor BDI score after 6 weeks of treatment when compared with baseline (before treatment). Metyrapone supplementation significantly reduced both HDRS and BDI scores after 6-week supplementation. Moreover, pharmacokinetic data indicate that metyrapone did not influence significantly the plasma concentration of imipramine and its metabolite, desipramine in the patients during joint treatment with metyrapone and imipramine, what suggests the lack of pharmacokinetic interaction. This preliminary study is the first demonstration of the benefit of metyrapone supplementation in imipramine therapy of treatment-resistant unipolar depression and suggests that a change in the level of neurotransmitters, hormones and immunological parameters, which are disturbed in depression, may contribute to the mechanism of the action of this drug.

Adult↗
PubMed1985

Effects of metyrapone on the pharmacological activity, plasma levels and urinary excretion of the dopamine receptor agonist DK-118.

Possible metabolic activation of the dopamine receptor agonist DK-118 (5-hydroxy-6-methyl-N,N-di-n-propyl-2-aminotetralin) was investigated in cats. Metyrapone, an inhibitor of oxidative drug metabolism, was given to cats before DK-118 and the pharmacologic effects of the dopamine agonist were compared to those observed in nonpretreated animals. A sensitive high-performance liquid chromatography assay using electrochemical detection was developed to monitor urine and plasma concentrations of DK-118 in metyrapone-pretreated and control animals. The DK-118-mediated inhibition of cardioaccelerator nerve stimulation-induced tachycardia was reduced markedly in cats pretreated with metyrapone but the pretreatment had no effect on the hypotension or bradycardia produced by DK-118. In a separate group of cats, the tachycardia inhibitory effect of a nonbioactivated dopamine agonist, dipropyldopamine, was unaffected by metyrapone pretreatment, confirming that the inhibitor of drug metabolism does not interfere with this dopamine receptor-mediated effect. Pretreatment with metyrapone before a 0.14-mumol/kg i.v. dose of DK-118 increased the half-life, reduced total drug clearance and increased urinary excretion of unchanged DK-118. All of the changes are consistent with a metyrapone-related inhibition of DK-118 metabolism. The results of this study show that inhibition of DK-118 metabolism reduces certain of its pharmacologic actions, indicating that one or more of the metabolites of the drug may contribute to its effects.

Animals↗
PubMed1979

[Effect of metyrapone on bile flow and bile acid excretion in Wistar rats].

The influence of metyrapone on bile flow and excretion of mono-(MBA), di-(DBA) and trihydroxy-(TBA)-bile acids was investigated in adult male Wistar rats after single and repeated pretreatment. MBA were not found in the rat bile. Metyrapone administration (200 mg/kg b.w. i.p.) 1 h before onset of a 3-hour bile collection period diminished bile flow and excretion of DBA and TBA. The relation TBA/DBA was changed towards DBA. Similar results were found after repeated administration 12 h after the last metyrapone injection (4 x 50 mg/kg b.w. i.p. per day for 4 consecutive days). But 60 h after the last metyrapone administration bile flow and the excretion of TBA were enhanced and the TBA/DBA ratio was changed towards TBA. The possible influence of metyrapone on bile acid hydroxylation is discussed and compared with metyrapone action on hydroxylation of foreign compounds.

Animals↗
PubMed2002

Metyrapone-induced corticosterone deficiency impairs glucose oxidation and steroidogenesis in Leydig cells of adult albino rats.

The present study was designed to identify the effects of metyrapone-induced corticosterone deficiency on Leydig cell steroidogenesis in adult male rats. Adult Wistar rats (200-250 g body weight) were treated with metyrapone, an inhibitor of corticosterone synthesis (10 mg/100 g body weight, s.c., twice daily) for 10 days. Experimental animals were killed along with controls, blood was collected, and sera separated for testosterone and estradiol assays. Testes were removed and Leydig cells were isolated, purified and used for estimating the specific activity of 17beta-hydroxysteroid dehydrogenase (17beta-HSD) and 14C-glucose oxidation. Serum testosterone (p < 0.05), Leydig cellular 14C-glucose oxidation (p < 0.001) and the specific activity of 17beta-HSD (p < 0.01) were significantly decreased in metyrapone treated rats. However, serum estradiol was not markedly altered compared to control. In addition to this, a set of in vitro experiments were also performed to identify the effects of metyrapone-induced corticosterone deficiency on hCG and prolactin-induced Leydig cell testosterone production. Metyrapone treatment significantly (p < 0.05) decreased the Leydig cellular basal as well as hCG and its combination with prolactin stimulated testosterone production in vitro. It is concluded from the present study that the inhibitory effects of metyrapone-induced corticosterone deficiency on Leydig cell steroidogenesis are mediated through impaired glucose oxidation and 17beta-HSD activity. In vitro studies showed that corticosterone deficiency impairs not only hCG action but also the potentiating effect of prolactin on Leydig cell steroidogenesis.

17-Hydroxysteroid Dehydrogenases↗
PubMed1987

Effects of metyrapone and etomidate on adrenal function and growth rate in female rats.

Two inhibitors of adrenal steroidogenesis were examined to determine whether the growth rate of female rats could be improved by lowering circulating plasma corticosterone concentrations. The first inhibitor, etomidate, is a potent narcotic agent and was found to have no effect on plasma corticosterone and deoxycorticosterone (DOC) concentrations at sub-narcotic doses. Growth rate, food intake, food conversion efficiency and adrenal weight were also unaffected by the drug. The second inhibitor, metyrapone, was shown in acute studies to have two distinct actions. In 6-week-old female rats moderate doses of metyrapone (50 mg/kg) had a stimulatory action resulting in increased plasma DOC and corticosterone concentrations. Higher doses of metyrapone (150-300 mg/kg) were increasingly less selective, causing an increase in plasma concentration of DOC, but attenuating the increase in corticosterone concentration, presumably by inhibiting the 11 beta-hydroxylase enzyme which allows the conversion of DOC to corticosterone. In adult rats (greater than 12 weeks old) the classical response to metyrapone was observed. Plasma DOC concentrations were increased, while corticosterone levels were reduced in a dose-dependent manner. In 5-week-old rats treated chronically, metyrapone (300 mg/kg) had no effect on plasma corticosterone, but increased plasma DOC concentration, depressed food intake and reduced growth rate. In 8-week-old rats treated chronically, the high dose of metyrapone (300 mg/kg) required to lower peak plasma corticosterone concentrations produced toxic effects resulting in the death of three animals. The remaining animals recovered rapidly, and gained more weight than controls over the final 6 days of the experiment. However, this experiment was terminated before the treated animals were able to catch up with the controls.(ABSTRACT TRUNCATED AT 250 WORDS)

Adrenal Glands↗
PubMed2000

Metyrapone, an inhibitor of corticosterone synthesis, blocks the kainic acid-induced expression of HSP 70.

It is shown in the present study that metyrapone (100 mg/kg), an inhibitor of corticosterone synthesis, given twice, 30 min before and 6 h after kainic acid (10 mg/kg) administration, blocks the kainic acid-evoked induction of heat shock proteins 72 kDa (HSP 70). Specifically, it was observed that metyrapone completely prevented kainic acid-induced appearance of HSP 70 in the rat amygdala, habenula, parietal cortex, and significantly decreased the number of HSP 70-positive neurons in the CA1, CA3, and CA4 subregions of hippocampus. The reduction in HSP 70 induction was paralleled by a complete prevention of the kainic acid-induced rise in the circulating corticosterone level by metyrapone; however, in applied doses metyrapone evoked slight enhancement of blood corticosterone. Despite the fact that metyrapone blocked/attenuated the kainic acid-evoked induction of HSP 70, its administration did not affect the behavioral effects of kainic acid, regarded as "limbic status epilepticus." It is concluded that the blockade of corticosterone synthesis might have neuroprotective effects in the pathological states associated with the overstimulation of glutamatergic receptors.

Animals↗
PubMedDate not supplied

An acute rise in serum phosphorus after single-dose oral metyrapone.

Metyrapone, an 11 beta-hydroxylase inhibitor, is widely used as a pharmacologic test for ACTH reserve. During studies on the pharmacodynamics of metyrapone and the response of plasma 11-deoxycortisol and cortisol, we fortuitously noted a consistent change in serum phosphate but no other routine laboratory chemistry determination. For these studies 12 control subjects were given oral methyrapone (30 mg/kg) at midnight. Serum phosphate (P) concentration was measured in fasting subjects at 08:00 on the morning before and after the administration of metyrapone. In 11 of 12 subjects, serum P increased from a mean of 3.6 +/- 0.7 (SD) mg/100 ml to a mean of 4.2 +/- 0.07 (SD) mg/100 ml on the morning following the drug. No increase in P was noted following the same dose of metyrapone in four patients on acute or chronic steroid therapy or in patients with primary or secondary hypoadrenocorticism. In addition, two addisonian patients were given either a saline or a hydrocortisone infusion for four hours. While the hydrocortisone infusion resulted in a drop in serum P, there was no decrease during saline infusions. These findings suggest that an acute rise in serum P after a single dose of metyrapone might be a rapid indicator of adrenocortical blockade leading to increased ACTH secretion, and cortisol and/or ACTH might play a role in P homeostasis.

Adult↗
PubMed2004

Investigation of the hypothalamo-pituitary-adrenal axis (HPA) by 1 microg ACTH test and metyrapone test in patients with primary fibromyalgia syndrome.

Primary fibromyalgia syndrome (PFS) is characterized by widespread chronic pain that affects the musculoskeletal system, fatigue, anxiety, sleep disturbance, headache and postural hypotension. The pathophysiology of PFS is unknown. The hypothalamic-pituitary-adrenal (HPA) axis seems to play an important role in PFS. Both hyperactivity and hypoactivity of the HPA axis have been reported in patients with PFS. In this study we assessed the HPA axis by 1 microg ACTH stimulation test and metyrapone test in 22 patients with PFS and in 15 age-, sex-, and body mass index (BMI)- matched controls. Metyrapone (30 mg/kg) was administered orally at 23:00 h and blood was sampled at 08:30 h the following morning for 11-deoxycortisol. ACTH stimulation test was carried out by using 1 microg (iv) ACTH as a bolus injection after an overnight fast, and blood samples were drawn at 0, 30 and 60 min. Peak cortisol level (659.4 +/- 207.2 nmol/l) was lower in the patients with PFS than peak cortisol level (838.7 +/- 129.6 nmol/l) in the control subjects (p < 0.05). Ten patients (45%) with PFS had peak cortisol responses to 1 microg ACTH test lower than the lowest peak cortisol detected in healthy controls. After metyrapone test 11-deoxycortisol level was 123.7 +/- 26 nmol/l in patients with PFS and 184.2 +/- 17.3 nmol/l in the controls (p < 0.05). Ninety five percent of the patients with PFS had lower 11-deoxycortisol level after metyrapone than the lowest 11-deoxycortisol level after metyrapone detected in healthy controls. We also compared the adrenal size of the patients with that of the healthy subjects and we found that the adrenal size between the groups was similar. This study clearly shows that HPA axis is underactivated in PFS, rather than overactivated.

Adrenal Glands↗
PubMed1982

The substituted pyridines metyrapone and nicotinamide are inducers of 5-aminolevulinate synthase and cytochrome P-450 in hepatocyte culture.

The effects of metyrapone and nicotinamide, two substituted pyridines, were studied in cultured chick embryo hepatocytes, a system characterized by preserved inducibility of cytochrome P-450 hemoproteins. Both metyrapone and nicotinamide caused a dose-dependent increase in cytochrome P-450 concentration. Their inducing potencies differed by one to two orders of magnitude and correlated with the known difference in the binding affinity of these two pyridines to cytochrome P-450. The increase of cytochrome P-450 concentration after metyrapone and nicotinamide was additive to the induction of cytochrome P-450 by phenobarbital and beta-naphthoflavone and was abolished by cycloheximide. Treatment of hepatocyte cultures with metyrapone resulted in an increase in a microsomal protein with an apparent mol. wt of 52,000. In addition, induction of cytochrome P-450 by the substituted pyridines was associated with enhanced 5-aminolevulinate synthase, the rate-limiting enzyme of heme biosynthesis. These data suggest that in cultured chick embryo hepatocytes the substituted pyridines metyrapone and nicotinamide induce cytochrome P-450.

5-Aminolevulinate Synthetase↗
PubMed1991

Reductive metabolism of metyrapone by a quercitrin-sensitive ketone reductase in mouse liver cytosol.

Mouse liver cytosol catalyses the reduction of metyrapone to the corresponding alcohol metabolite metyrapol. The enzyme involved was characterized as a NADPH-dependent carbonyl reductase which is strongly inhibited by the plant flavonoid quercitrin but which shows no sensitivity to phenobarbital. Thus, by inhibitor subdivision of carbonyl reductases the metyrapone reductase in mouse liver cytosol has to be classified as a ketone reductase rather than an aldehyde reductase, as it was shown previously for the analogous enzyme in mouse liver microsomes based on the same pattern of inhibitor classification. Moreover, immunological comparison of the metyrapone reductases from the two subcellular fractions reveal no common antigenic determinants indicating the structural difference between these enzymes. In conclusion, metyrapone undergoes reductive biotransformation mediated by two clearly distinct carbonyl reductases located in different subcellular compartments of mouse liver cells. Considering the convenient and sensitive HPLC-method for direct metyrapol determination, metyrapone may serve as a useful tool in the investigation of these enzymes, although their physiological roles remain to be determined.

Alcohol Oxidoreductases↗
PubMed1983

Synthesis of radioiodinated metyrapone--a potential adrenal imaging agent.

Metyrapone has been labelled with radioiodine selectively in the 4'-position of ring B. The synthesis of 123I-(131)-metyrapone involves four intermediate compounds. 4'-Bromo-metyrapone serves as a stable precursor that is labelled before use. Studies of the biodistribution of [131I]metyrapone in rats indicate the highest concentration in the adrenal gland 10 min after the injection with a fast elimination of the radioactivity. However, the absolute uptake in the normal adrenal is low. When [123I]metyrapone was used in a patient with bilateral hyperplasia, faint adrenal images were obtained.

Adrenal Glands↗
PubMed1985

Adrenal cortical 11 beta-hydroxylase and side-chain cleavage enzymes. Requirement for the A- or B-pyridyl ring in metyrapone for inhibition.

The adrenal cortical enzyme systems, 11 beta-hydroxylase, P-450 11 beta, and the side-chain cleavage complex, P-450 scc, differ only in their cytochrome P-450s. Structural modifications of metyrapone, an inhibitor of cytochrome P-450 enzyme systems, have been made to determine the requirement for the A- or B-pyridyl ring for inhibition of P-45011 beta and P-450 scc activities. Three new analogs of metyrapone (A-phenylmetyrapone, B-phenylmetyrapone and diphenylmetyrapone) were synthesized and evaluated as inhibitors using a crude, defatted bovine adrenal cortical mitochondrial preparation. Characterization of the mitochondrial preparation demonstrated: enhancement of both activities by the addition of 15.0 microM adrenodoxin, the addition of 1% ethanol decreased both activities less than 10%, and the apparent Km of deoxycorticosterone for P-45011 beta was 6.8 microM and the apparent Km of cholesterol for P-450 scc was 21.6 microM. Inhibition of P-45011 beta and P-450 scc activities with these compounds demonstrated: the B-pyridyl ring of metyrapone is required for inhibition of both activities whereas requirement for the A-ring is less stringent, and the four metyrapone analogs were more selective inhibitors of P-45011 beta activity. These studies suggest that the A-phenyl metyrapone analog is a good candidate for further development of a selective adrenocortical radiopharmaceutical.

Adrenal Cortex↗
PubMed1984

The metyrapone test in affective disorders and schizophrenia II. Changes upon treatment.

The metyrapone test was applied to groups of patients suffering from major depressive illness with melancholia, mania or schizophrenia, before and after treatment. There were interesting individual correlations between post-metyrapone cortexolone values, cortexolone/cortisol ratios and clinical improvement in depressives. Two patients who had exhibited abnormal metyrapone responses displayed a normalization of post-metyrapone cortexolone values upon clinical improvement, whereas the opposite trend was observed in a patient who did not improve and in another who became manic. These preliminary results may indicate that abnormal metyrapone responses in depression are state dependent.

Adult↗