Effects of spironolactone, canrenone and canrenoate-K on cytochrome P450, and 11beta- and 18-hydroxylation in bovine and human adrenal cortical mitochondria

Spontaneous Remission of Primary Aldosteronism with Mineralocorticoid Receptor Antagonist Therapy: A Review

In this review, we describe previous basic and clinical studies on autonomous aldosterone production. Over the past decades, mineralocorticoid receptor antagonists (MRAs) have been found to concentration-dependently inhibit steroidogenesis in different degrees. However, many studies have proven the suppressive effects of MRAs on the activities of hormone synthase. The probable factors of cytochrome P-450 reduction, both in microsomes and mitochondria, have also been considered: (1) one of the spironolactone metabolite forms had destructive function, except canrenone, (2) 7α-thio-spironolactone was an obligatory intermediate in the spironolactone-induced CYP450 decrease, and (3) the contributing steroids should have 7α-methylthio or 7α-methylsulfone groups. In previous clinical research, spironolactone-body-containing cells showed a type II pattern of enzyme activity (i.e., enhanced 3β-hydroxysteroid dehydrogenase, glucose-6-phosphate, and NADP-isocitrate dehydrogenase activities and weaken succinate dehydrogenase activity), and the subcapsular micronodules composed of spironolactone-body-containing cells also exhibited a type II pattern and excess aldosterone secretion, indicating that the subcapsular micronodules might be the root of aldosterone-producing adenoma. Moreover, combined with the potential impeditive function to aldosterone secretion, a few cases of spontaneous remission of primary aldosteronism, with normal ranges of blood pressure, plasma potassium, plasma renin activity, and aldosterone renin ratio, have been reported after long-term treatment with MRAs.

Human cytochrome P450 enzymes 5-51 as targets of drugs and natural and environmental compounds: mechanisms, induction, and inhibition - toxic effects and benefits

Cytochrome P450 (P450, CYP) enzymes have long been of interest due to their roles in the metabolism of drugs, pesticides, pro-carcinogens, and other xenobiotic chemicals. They have also been of interest due to their very critical roles in the biosynthesis and metabolism of steroids, vitamins, and certain eicosanoids. This review covers the 22 (of the total of 57) human P450s in Families 5-51 and their substrate selectivity. Furthermore, included is information and references regarding inducibility, inhibition, and (in some cases) stimulation by chemicals. We update and discuss important aspects of each of these 22 P450s and questions that remain open.

Biotransformation of the mineralocorticoid receptor antagonists spironolactone and canrenone by human CYP11B1 and CYP11B2: Characterization of the products and their influence on mineralocorticoid receptor transactivation

Spironolactone and its major metabolite canrenone are potent mineralocorticoid receptor antagonists and are, therefore, applied as drugs for the treatment of primary aldosteronism and essential hypertension. We report that both compounds can be converted by the purified adrenocortical cytochromes P450 CYP11B1 and CYP11B2, while no conversion of the selective mineralocorticoid receptor antagonist eplerenone was observed. As their natural function, CYP11B1 and CYP11B2 carry out the final steps in the biosynthesis of gluco- and mineralocorticoids. Dissociation constants for the new exogenous substrates were determined by a spectroscopic binding assay and demonstrated to be comparable to those of the natural substrates, 11-deoxycortisol and 11-deoxycorticosterone. Metabolites were produced at preparative scale with a CYP11B2-dependent Escherichia coli whole-cell system and purified by HPLC. Using NMR spectroscopy, the metabolites of spironolactone were identified as 11β-OH-spironolactone, 18-OH-spironolactone and 19-OH-spironolactone. Canrenone was converted to 11β-OH-canrenone, 18-OH-canrenone as well as to the CYP11B2-specific product 11β,18-diOH-canrenone. Therefore, a contribution of CYP11B1 and CYP11B2 to the biotransformation of drugs should be taken into account and the metabolites should be tested for their potential toxic and pharmacological effects. A mineralocorticoid receptor transactivation assay in antagonist mode revealed 11β-OH-spironolactone as pharmaceutically active metabolite, whereas all other hydroxylation products negate the antagonist properties of spironolactone and canrenone. Thus, human CYP11B1 and CYP11B2 turned out to metabolize steroid-based drugs additionally to the liver-dependent biotransformation of drugs. Compared with the action of the parental drug, changed properties of the metabolites at the target site have been observed.

Estimation of the Mechanism of Adrenal Action of Endocrine-Disrupting Compounds Using a Computational Model of Adrenal Steroidogenesis in NCI-H295R Cells

Adrenal toxicity is one of the major concerns in drug development. To quantitatively understand the effect of endocrine-active compounds on adrenal steroidogenesis and to assess the human adrenal toxicity of novel pharmaceutical drugs, we developed a mathematical model of steroidogenesis in human adrenocortical carcinoma NCI-H295R cells. The model includes cellular proliferation, intracellular cholesterol translocation, diffusional transport of steroids, and metabolic pathways of adrenal steroidogenesis, which serially involve steroidogenic proteins and enzymes such as StAR, CYP11A1, CYP17A1, HSD3B2, CYP21A2, CYP11B1, CYP11B2, HSD17B3, and CYP19A1. It was reconstructed in an experimental dynamics of cholesterol and 14 steroids from an in vitro steroidogenesis assay using NCI-H295R cells. Results of dynamic sensitivity analysis suggested that HSD3B2 plays the most important role in the metabolic balance of adrenal steroidogenesis. Based on differential metabolic profiling of 12 steroid hormones and 11 adrenal toxic compounds, we could estimate which steroidogenic enzymes were affected in this mathematical model. In terms of adrenal steroidogenic inhibitors, the predicted action sites were approximately matched to reported target enzymes. Thus, our computer-aided system based on systems biological approach may be useful to understand the mechanism of action of endocrine-active compounds and to assess the human adrenal toxicity of novel pharmaceutical drugs.

The Effect of Chronic Administration of Saffron (Crocus sativus) Stigma Aqueous Extract on Systolic Blood Pressure in Rats

Background

Crocus sativus L. (saffron), which belongs to the Iridaceae family, is widely cultivated in Iran. Cardiovascular effects of saffron has been established in some studies but the effects of chronic administration of saffron (C. sativus) stigma aqueous extract on blood pressure has not been investigated.

Objectives

In this study the effects of saffron (C. sativus) stigma aqueous extract on blood pressure of normotensive and desoxycorticosterone acetate (DOCA)-salt induced hypertensive rats, in chronic exposure was evaluated.

Materials and Methods

Five weeks administration of three doses saffron aqueous extract (10, 20 and 40 mg/Kg/day) and spironolactone (50 mg/Kg/day) in different groups of normotensive and hypertensive rats (at the end of 4 weeks treatment by DOCA-salt) was carried out and their effects on mean systolic blood pressure (MSBP) and heart rate (HR) were evaluated using tail cuff method. The duration of the effect of saffron on systolic blood pressure (SBP), was also evaluated.

Results

Our results indicated that chronic administration of saffron aqueous extract could reduce the MSBP in DOCA salt treated rats in a dose dependent manner. This compound did not decrease the MSBP in normotensive rats. The data also showed that antihypertensive effects of saffron did not persist.

Conclusions

It is concluded that saffron aqueous extract possesses antihypertensive and normalizing effect on BP in chronic administration.

The effect of spironolactone upon corticosteroid hormone metabolism in patients with early stage chronic kidney disease

CONTEXT

Aldosterone has emerged as an important mediator of disease progression and mortality in patients with chronic heart and kidney disease (CKD). Despite the increasing use of mineralocorticoid receptor antagonists in these patients, little is known about the effects on corticosteroid hormone secretion and metabolism.

OBJECTIVE

To assess corticosteroid hormone secretion and metabolism in patients with early stage CKD before and after spironolactone (Spiro).

DESIGN

Randomized, double-blind, placebo-controlled interventional study.

SETTING

Single tertiary referral centre.

PATIENTS

A total of 112 patients with stable stage 2/3 CKD.

INTERVENTIONS

Patients were randomized to receive either Spiro 25 mg once daily or placebo for 36 weeks.

MAIN OUTCOME MEASURES

Plasma renin activity (PRA), angiotensin II (AngII) and steroid hormones were analysed by standard assays; urinary corticosteroid hormone metabolites (5α+5β-tetrahydro-cortisol (5α+5β-THF), TH-cortisone (THE), 3α5β-TH-aldosterone (TH-Aldo), 5α+5β-TH-deoxycorticosterone (5α+5β-TH-DOC), TH-11-desoxycortisol (THS)) were analysed by gas chromatography/mass spectrometry.

RESULTS

Plasma aldosterone concentration (PAC) was inversely correlated with eGFR (r = -0·331, P < 0·001). Urinary 24-h excretion of TH-Aldo was correlated with PAC (r = 0·214, P < 0·05) and diastolic blood pressure (BP) (r = 0·212, P = <0·05), whereas total 24-h urinary cortisol metabolite excretion was correlated with systolic BP (r = 0·316, P < 0·01). In addition, 11β-hydroxysteroid dehydrogenase (11β-HSD) type 1 activity (urinary 5α+5β-THF)/THE) ratio) was correlated with PRA (r = 0·277, P < 0·01). Spiro treatment significantly reduced BP (123 ± 11/76 ± 7 vs 119 ± 11/73 ± 8 mmHg, P < 0·01) despite renin-angiotensin-aldosterone system induction, reflected by increased urinary 24-h TH-Aldo excretion (17·6 (12, 86) vs 26 (18, 80) μg/24 h, P < 0·05). By contrast, Spiro had no effect on total urinary cortisol metabolite excretion, 11β-hydroxylase, 11β-HSD type 1 and 2 activity.

CONCLUSIONS

Aldo and cortisol are positively associated with BP suggesting that adrenal hyperactivity may in part explain the increased cardiovascular risk in patients with early end-stage CKD. Addition of Spiro had no effect on glucocorticoid metabolism or total 24-h corticosteroid production.

Effect of acute and prolonged mineralocorticoid receptor blockade on spontaneous and stimulated hypothalamic-pituitary-adrenal axis in humans

CONTEXT

Mineralocorticoid receptors (MRs) in the hippocampus display an important role in the control of the hypothalamic-pituitary-adrenal (HPA) axis, mediating the proactive feedback of glucocorticoids, which maintains the basal HPA activity. The systemic administration of MR antagonists enhances spontaneous and CRH-stimulated ACTH, cortisol, and DHEA secretion, while the effects of chronic treatment with MR antagonists are scanty. Our study was performed in order to clarify this point.

DESIGN

ACTH, cortisol, and DHEA levels were studied during the infusion of placebo, canrenoate, a MR antagonist (CAN, 200 mg i.v. bolus at 1600 h followed by 200 mg infused over 4 h), and human CRH (hCRH; 2.0 microg/kg i.v. bolus at 1800 h) before and during the last week of 28-day treatment with CAN (200 mg/day p.o.) in eight young women.

RESULTS

Pre-treatment sessions: CAN and hCRH administration increased ACTH, cortisol, and DHEA levels versus placebo (P<0.05). Post-treatment sessions: during placebo infusion, cortisol and DHEA were significantly amplified versus pre-treatment session (P<0.05), while ACTH levels were not modified; CAN infusion, differently from pre-treatment session, was not able to significantly increase ACTH, cortisol, and DHEA levels; ACTH, cortisol, and DHEA responses to hCRH were amplified with respect to pre-treatment session, although statistical significance was obtained for cortisol and DHEA only.

CONCLUSIONS

MR blockade by acute CAN administration significantly enhances the HPA activity in the afternoon, during the quiescent phase of the circadian rhythm. At the same period, prolonged treatment with CAN amplifies both spontaneous and CRH-stimulated activities of the HPA axis, while it blunts the HPA responsiveness to a further MR-mediated stimulation.

Contrasting effects of eplerenone and spironolactone on adrenal cell steroidogenesis

Spironolactone and eplerenone are widely used as mineralocorticoid antagonists. Spironolactone has several nonspecific actions including inhibition of androgen receptor and steroid hormone biosynthesis. While studies have shown that eplerenone does not exhibit nonspecific actions on androgen receptor, its effects on steroid hormone production have not been reported. Herein, the effects of eplerenone (0.1-30 microM) and spironolactone (0.1-30 microM) on steroid production were examined in human adrenocortical H295R cells. Spironolactone inhibited basal production of cortisol (91%) and aldosterone (53%). Treatment of H295R cells with angiotensin II (Ang II) for 24 h increased aldosterone production by 11-fold. Spironolactone inhibited Ang II stimulation of aldosterone production by 80%. Addition of pregnenolone increased aldosterone (9-fold) and cortisol (3-fold) production. Spironolactone inhibited pregnenolone metabolism to aldosterone (67%) and cortisol (74%). The inhibitory effects of spironolactone occurred at concentrations far higher than those needed to block mineralocorticoid receptor, suggesting an action directly on the enzymes involved in steroid production. In contrast, eplerenone did not inhibit basal, Ang II, forskolin, pregnenolone-stimulated cortisol, or aldosterone production. Together, these data demonstrate that opposed to spironolactone, pharmacologic concentrations of eplerenone do not inhibit adrenal cell aldosterone or cortisol production.

Analysis of mRNA expression for steroidogenic enzymes in the remaining adrenal cortices attached to adrenocortical adenomas

DESIGN AND METHODS

We have recently demonstrated that the adrenal cortices attached to aldosterone-producing adenoma (APA) contained microscopic subcapsular micronodules suggestive of active aldosterone production. In this study, we used in situ hybridization to investigate the mRNA expression of steroidogenic enzymes in the adrenal cortices attached to cortisol-producing adenoma (CPA) and clinically silent adenoma (non-functioning adenoma; NFA), in addition to APA.

RESULTS

Microscopic subcapsular micronodules, which were several hundreds of micrometers in size and spheroid in shape, were observed in the cortices attached to CPA and NFA, as well as APA, at high frequency. Most of the cortical nodules in zona fasciculata to zona reticularis showed a suppressed steroidogenesis in the cortices attached to adenoma, but some expressed intensely all necessary steroidogenic enzyme mRNAs for cortisol synthesis.

CONCLUSIONS

It is thus necessary to keep in mind, on the occasion of subtotal adrenalectomy, that lesions with the potential to later develop into functional adrenocortical nodules may be present in other parts of the ipsilateral or contralateral adrenal cortices.

Analysis of unilateral adrenal hyperplasia with primary aldosteronism from the aspect of messenger ribonucleic acid expression for steroidogenic enzymes: a comparative study with adrenal cortices adhering to aldosterone-producing adenoma

Unilateral adrenal hyperplasia with primary aldosteronism is very rare and shows similar endocrine features to aldosterone-producing adenoma and bilateral adrenal hyperplasia. In this study, the mRNA expression of steroidogenic enzymes in unilateral adrenal hyperplasia was examined by in situ hybridization. We found subcapsular micronodules composed of spironolactone body-containing cells, which showed intense expression for 3beta-hydroxysteroid dehydrogenase, 11beta-hydroxylase, 18-hydroxylase, and 21-hydroxylase but not 17alpha-hydroxylase, indicating aldosterone production. This expression pattern was the same as that in unilateral multiple adrenocortical micronodules, reported recently. Additionally, it was noted that a nodule with active aldosterone production was closely adjacent to one showing intense 17alpha-hydroxylase expression. In the adrenal cortices adhering to aldosterone-producing adenoma, the majority of hyperplastic zona glomerulosa and hyperplastic nodules demonstrated a decreased steroidogenic activity. However, minute nodules indicative of active aldosterone production were found at high frequency. These results suggest that the subcapsular micronodules observed might be the root of aldosterone-producing adenoma. Furthermore, we emphasize the need for long-term follow-up after unilateral adrenalectomy or enucleation of the adenoma because of the possibility that buds with autonomous aldosterone production may still be present in the contralateral or remaining adrenal tissue.

CYP17- and CYP11B-dependent steroid hydroxylases as drug development targets

Steroid hormone biosynthesis is catalyzed by the action of a series of cytochrome P450 enzymes as well as reductases. Defects in steroid hydroxylating P450s are the cause of several severe defects such as the adrenogenital syndrome (AGS), corticosterone methyl oxidase (CMO) I or II deficiencies, or pseudohermaphroditism. In contrast, overproduction of steroid hormones can be involved in breast or prostate cancer, in hypertension, and heart fibrosis. Besides inhibiting the action of the steroid hormones on the level of steroid hormone receptors by using antihormones, which often is connected with severe side effects, more recently the steroid hydroxylases themselves turned out to be promising new targets for drug development. Since the 3-dimensional structures of steroid hydroxylases are not yet available, computer models of the corresponding CYPs may help to develop new inhibitors of these enzymes. During the past years, the necessary test systems have been developed and new compounds have been synthesized, which displayed selective and specific inhibition of CYP17, CYP11B2, and CYP11B1. With some of these potential new drugs, clinical trials are under way. It can be expected that in the near future some of these compounds will contribute to our arsenal of new and selective drugs.

Hypothalamus-pituitary-adrenal hyperactivity in human aging is partially refractory to stimulation by mineralocorticoid receptor blockade

CONTEXT

The hypothalamus-pituitary-adrenal (HPA) axis is mainly regulated by CRH, arginine vasopressin, and glucocorticoid feedback. Hippocampal mineralocorticoid receptors mediate proactive glucocorticoid feedback and mineralocorticoid antagonists, accordingly, stimulate HPA axis. Age-related HPA hyperactivity reflects impaired glucocorticoid feedback at the suprapituitary level.

DESIGN

ACTH, cortisol, and dehydroepiandrosterone (DHEA) secretion were studied in eight healthy elderly (75.1 +/- 3.2 yr) and eight young (25.0 +/- 4.6 yr) subjects during placebo or canrenoate (CAN) administration (200 mg i.v. bolus followed by 200 mg infused over 4 h).

RESULTS

During placebo administration, ACTH and cortisol areas under the curve (AUCs) in elderly subjects were higher than in young subjects (P < or = 0.01); conversely, DHEA AUCs in elderly subjects were lower than in young subjects (P = 0.002). CAN increased ACTH, cortisol, and DHEA levels in both groups. In young subjects, ACTH, cortisol, and DHEA levels at the end of CAN infusion were higher (P < or = 0.05) than after placebo. In elderly subjects, at the end of CAN infusion, ACTH, cortisol, and DHEA levels were higher (P = 0.01) than after placebo. Under CAN, ACTH and cortisol AUCs were persistently higher (P < or = 0.01) and DHEA AUCs lower (P = 0.006) in elderly than in young subjects. Cortisol AUCs after CAN in young subjects did not become significantly different from those in elderly subjects after placebo.

CONCLUSIONS

1) Evening-time ACTH and cortisol secretion in elderly subjects is higher than in young subjects; 2) ACTH and cortisol secretion in elderly subjects is enhanced by CAN but less than that in young subjects; and 3) DHEA hyposecretion in elderly subjects is partially restored by mineralocorticoid antagonism. Age-related variations of HPA activity may be determined by some derangement in mineralocorticoid receptors function at the hippocampal level.

The human steroid hydroxylases CYP1B1 and CYP11B2

Major advances have been made during the last decade in our understanding of adrenal steroid hormone biosynthesis. Two key players in these pathways are the human mitochondrial cytochrome P450 enzymes CYP11B1 and CYP11B2, which catalyze the final steps in the biosynthesis of cortisol and aldosterone. Using data from mutations found in patients suffering from steroid hormone-related diseases, from mutagenesis studies and from the construction of three-dimensional models of these enzymes, structural information could be deduced that provide a clue to the stereo- and regiospecific steroid hydroxylation reactions carried out by these enzymes. In this review, we summarize the current knowledge on the physiological function and the biochemistry of these enzymes. Furthermore, the pharmacological and toxicological importance of these steroid hydroxylases, the means for the identification of their potential inhibitors and possible biotechnological applications are discussed.

Development of a test system for inhibitors of human aldosterone synthase (CYP11B2): screening in fission yeast and evaluation of selectivity in V79 cells

Aldosterone synthase (CYP11B2) is a mitochondrial cytochrome P450 enzyme catalyzing the last steps of aldosterone production in the adrenal cortex. A new pharmacological approach for the treatment of the aldosterone induced effects in congestive heart failure and all forms of hyperaldosteronism could be the use of CYP11B2 inhibitors. In search for such compounds, it was our goal to develop a cellular enzyme assay suitable for screening high numbers of compounds. An assay procedure for the evaluation of inhibitors using the human CYP11B2 expressed in fission yeast Schizosaccharomyces pombe was established and a series of 10 compounds was tested in this whole cellular system. Human 11beta-hydroxylase (CYP11B1), which catalyzes the production of glucocorticoids, shows more than 90% homology compared to human CYP11B2. As this enzyme should not be affected, strong inhibitors of CYP11B2 have to be tested for selectivity. For that purpose, an assay procedure with V79MZ cells that express human CYP11B1 and CYP11B2, respectively, was integrated into the evaluation process. Using these screening procedures a potent and rather selective non-steroidal inhibitor of human CYP11B2 was detected with an IC(50) value of 59nM. We also identified a very potent inhibitor of both enzymes showing a stronger inhibitory activity against the cortisol producing CYP11B1.

Suppression of surgical hyperaldosteronism by potassium canrenoate during gynecologic surgery under sevoflurane anesthesia

BACKGROUND

Surgical hyperaldosteronism leads to sodium and water retention during surgery and often causes postoperative edema. This study investigated the effect of potassium canrenoate (PC) on pituitary adrenocortical function in lower abdominal surgery under sevoflurane anesthesia.

METHODS

Twenty patients were randomized to receive 400 mg of PC (the PC group, n=10) or saline (the control group, n=10) intravenously. The following parameters were determined: plasma aldosterone, adrenocorticotropic hormone (ACTH), plasma renin activity (PRA), serum sodium and potassium, urinary sodium and potassium, and urine output.

RESULTS

The aldosterone and ACTH levels showed significant increases in the control group during surgery. Plasma ACTH also increased significantly in the PC group, but plasma aldosterone levels were unchanged during surgery. The urine Na/K ratio of the PC group was significantly higher than that of the control group.

CONCLUSION

The present study suggested that PC suppresses the increase of plasma aldosterone caused by surgical stress. That may prevent sodium retention and potassium excretion during surgery.

Spironolactone as a single agent for long-term therapy of hirsute patients

OBJECTIVE

To assess the androgen-suppressing effect of spironolactone, and the use of this drug as a single agent in the long-term therapy of hirsute patients with either polycystic ovary syndrome (PCOS) or idiopathic hirsutism (IH). Standard cyproterone acetate (CPA) treatment was used to evaluate the results obtained with spironolactone.

DESIGN

Prospective randomized study.

PATIENTS

Forty-six hirsute women were separated randomly into two groups, stratified for polycystic ovary syndrome. For 12 months, Group 1 (21 patients, 10 PCOS) received spironolactone only (200 mg/day). Group 2 (23 patients, nine PCOS) received CPA (50 mg/day) with ethinyl oestradiol (35 microgram/day).

MEASUREMENTS

Ferriman-Gallwey clinical score for hirsutism and serum testosterone, androstenedione, and LH levels.

RESULTS

In IH patients, hirsutism regressed equally with spironolactone (21 +/- 2-14.5 +/- 2) and CPA (23 +/- 2-13 +/- 2). In PCOS patients, the mean score for hirsutism after 12 months was significantly lower with CPA (12 +/- 1) than with spironolactone (16 +/- 1). Testosterone levels did not change with spironolactone; with CPA there was a decrease from baseline in PCOS (47% and 51%, 6 and 12 months) and IH patients (31% and 30%). Androstenedione levels also declined from baseline in CPA-treated PCOS patients (38% and 39%, 6 and 12 months). Androgen levels were significantly different between the groups after 6 and 12 months. LH levels decreased with CPA (72%) but not with spironolactone.

CONCLUSION

Our results suggest that spironolactone used as a single agent is as effective as cyproterone acetate combined with oestradiol for long-term treatment of patients with idiopathic hirsutism. In PCOS patients, spironolactone is still effective for reducing hirsutism; however, for treatment of the hormonal or metabolic manifestations associated with PCOS, it may be necessary to combine spironolactone with either an antigonadotrophic agent or a drug that improves peripheral insulin sensitivity.

Influence of spironolactone on neonatal screening for congenital adrenal hyperplasia

AIM

To determine if the diuretic spironolactone cross reacts with 17alpha-hydroxyprogesterone (17OHP) in an enzyme linked immunosorbent assay (ELISA) kit used for the mass screening of congenital adrenal hyperplasia.

METHODS

Concentrations of 17OHP on a blood filter paper disc were measured using an ELISA kit (kit C-7: ENZAPLATE N-17alpha -OHP-7; Chiron, Tokyo, Japan). The cross reactivity of spironolactone and its metabolites with 17OHP was determined. The concentrations of spironolactone and its metabolites in blood were measured using HPLC (high performance liquid chromatography).

RESULTS

Spironolactone cross reacted with 17OHP using kit C-7 (0.01%), by increasing 17OHP concentration in a dose dependent manner. The blood concentration of spironolactone and its metabolites was nearly 900 ng/ml, high enough to show an additive effect on the 17OHP concentration. About 12% of the false positive cases screened using the kit were due to the administration of spironolactone.

CONCLUSIONS

Spironolactone interferes with 17OHP concentrations, leading to false positive test results for CAH.

Blocking of central nervous mineralocorticoid receptors counteracts inhibition of pituitary-adrenal activity in human sleep

Pituitary-adrenal activity has been found to be inhibited during early nocturnal sleep in humans. This inhibition was supposed to reflect a regulatory influence of hippocampal cells characterized by the expression of mineralocorticoid receptors (MR). Pituitary adrenal responsiveness to bolus injections of CRH (50 micrograms) was examined in each of nine healthy men on four occasions: CRH was injected either during early nocturnal sleep or at the same time of night while the subject was kept awake. Both of these conditions were run after pretreatment with the selective MR antagonist, canrenoate (2 x 200 mg, 0800 and 1700 h, preceding the experimental night) and after placebo administration. After placebo, sleep reduced ACTH and cortisol secretory responses to CRH to about 65% of the size observed during wakefulness (P < 0.05). After canrenoate, ACTH and cortisol secretory responses during sleep and wakefulness did not differ and were comparable with those obtained in placebo-treated subjects during wakefulness. Compared with placebo, canrenoate also distinctly reduced the time spent in slow-wave sleep (P < 0.005). The findings confirm an inhibition of pituitary-adrenal responsiveness during early sleep. The inhibition disappearance after blockage of MR suggests that sleep exerts this influence via central nervous MR-expressing cells. These cells seem to be simultaneously involved in the generation of slow-wave sleep.

Human adrenal CYP11B1: localization by in situ-hybridization and functional expression in cell cultures

CYP11B1 was detected in the human adrenal cortex and in human adenomas by in situ-hybridization methods. Specific riboprobes were generated and hybridized to sections of an Aldosterone Producing Adenoma (APA), the non-tumour portion of the corresponding adrenal gland and two adenomas not related to hyperaldosteronism. P45011B1 mRNA was clearly localized in the zona fasciculata/reticularis. Semi-quantitative analysis has been performed and seems to be applicable for a further classification of adrenal tumours. Stable expression of CYP11B1 cDNA was performed in V79 cells. The interference of different substances (metyrapone, spironolactone and different imidazole derivatives) with CYP11B1 activity was studied using this cell line. The cell line revealed to be suitable for analysis of the active site of CYP11B1 as well as for analysis of side effects of drugs on steroidogenesis.

Cellular and molecular aspects of the renal effects of diuretic agents

In the past few years, increased knowledge of the nature of transport proteins and their molecular regulation in the translocation of ions across kidney membranes has emerged. We are beginning to better understand the characteristics of the interaction of diuretics with these transport proteins. It is likely that this knowledge will permit further insight into nephron function regulation.

Comparative dose-effect studies with four C-17-spirosteroidal mineralocorticoid synthesis inhibitors

Interference of three spirolactones and a spiro-oxazolidine with mineralocorticoid biosynthesis in the concentration range of 10(-4)-10(-10) M has been studied in isolated dispersed z. glomerulosa cells. Inhibitory effects on several enzyme activities involved in the late steps of aldosterone synthesis have been determined. Different patterns of enzyme inhibition could be observed for each inhibitor. The points of interference were mostly related to cytochrome P450-C11-activities (i.e. 11 beta-/18-hydroxylation and 18-OH-oxidation).

The reoxidation of cytochrome P-450 by paraquat inhibits aldosterone biosynthesis from 18-hydroxycorticosterone

Paraquat is an artificial electron carrier that captures electrons from reduced cytochrome P-450 instead of the natural acceptors, thus decreasing the concentration of reduced mitochondrial cytochrome P-450. In the present study, paraquat inhibited the biosynthesis of aldosterone from 18-hydroxycorticosterone by mitochondria from duck adult adrenal gland, under aerobic conditions. Since paraquat did not induce any change in the absorption spectrum of highly purified cytochrome P-450 11 beta, the possibility of a displacement of steroid by the drug is ruled out. Moreover, paraquat did not affect oxidative phosphorylating chain nor did it alter by itself the chemical structure of 18-hydroxycorticosterone. In our conditions, the inhibitory role of paraquat seems restricted to a capture of electrons from reduced cytochrome P-450. Under the same conditions metopirone and spironolactone, known to bind cytochrome P-450 11 beta at the steroid binding site, also inhibited the reaction. Altogether these results show that for aldosterone synthesis from 18-hydroxycorticosterone to take place, the steroid binding site on cytochrome P-450 must be accessible to 18-hydroxycorticosterone and that the cytochrome P-450 must be the direct donor of reducing equivalents. Hence, cytochrome P-450 appears as the final linking point between 18-hydroxycorticosterone and the reducing equivalents provided by NADPH.

Adrenal mitochondrial metabolism of spironolactone. Absence of metabolic activation

Previous investigations have established that spironolactone (SL) administration to guinea pigs decreases adrenal mitochondrial and microsomal cytochrome P-450 content, and that the latter requires microsomal activation of the drug. Studies were carried out to determine if adrenal mitochondrial metabolism (activation) of SL was similarly involved in the effects of the drug on mitochondrial cytochrome P-450 destruction. Incubation of guinea pig adrenal mitochondria with SL in the absence of NADPH resulted in the formation of 7 alpha-thio-SL as the only metabolite. In the presence of an NADPH-generating system, an unknown polar metabolite was also produced. The mass spectrum of the unknown compound suggested that it was a hydroxylated derivative of SL. Incubation of mitochondrial preparations with 7 alpha-thio-SL also resulted in the formation of a polar metabolite, but the latter had a different HPLC retention time than that of the SL metabolite. Formation of the polar SL metabolite was prevented by metyrapone, an 11 beta-hydroxylase inhibitor, and was greatest in mitochondria from the adrenal zone having the highest 11 beta-hydroxylase activity. Steroid substrates for 11 beta-hydroxylation inhibited the production of the SL metabolite. Mitochondrial incubations with SL or with 7 alpha-thio-SL in the presence or absence of an NADPH-generating system did not affect cytochrome P-450 concentrations. The results indicate that, unlike the microsomal effects of SL, local activation of SL is not responsible for the destruction of adrenal mitochondrial cytochromes P-450. The major adrenal mitochondrial metabolites of SL appear to be 11 beta-hydroxy-SL and 7 alpha-thio-SL.

Effects of adrenalectomy and spironolactone on urinary metabolites of aldosterone in rats

The quantities and temporal sequences of appearance of aldosterone metabolites in the urine of adrenalectomized rats, and adrenalectomized rats treated with spironolactone, were compared following subcutaneous administration of a physiological dosage (0.05 microgram) of [1,2,-3H]aldosterone. Large amounts of radiometabolites were rapidly excreted during 0-1 and 1-3 h and only small quantities by 3-4 h in urine of both groups of rats. The majority of the urinary radiometabolites (70-85%) were identified by Sephadex DEAP-LH-20 chromatography as neutral metabolites of aldosterone (NMA), together with lesser quantities of acidic, sulfate, and glucuronide conjugates. Further characterization by high pressure liquid chromatography (HPLC) showed that 90% of the NMA excreted by adrenalectomized rats were polar metabolites which could be separated into at least 15 peaks eluting in regions of increasing polarity (designated A, B, C, and D). Only small quantities of unaltered [3H]aldosterone and no ring-A-reduced metabolites were excreted by the adrenalectomized rats. Spironolactone treatment caused large changes in the excretion of acidic and sulfate derivatives of aldosterone, as well as discrete alterations in the HPLC patterns of the polar NMA (particularly those metabolites in regions A and B). Such discrete changes in these metabolic pathways which occur at the same time as the hormonal actions of aldosterone in the kidney may provide further insight into understanding the biological role of aldosterone metabolism.

Relative inhibitory potency of five mineralocorticoid antagonists on aldosterone biosynthesis in vitro

Spirolactones are mineralocorticoid antagonists which bind to aldosterone receptors in the distal nephron. During the last decade, several antimineralocorticoids, which are more potent than spironolactone in competing for mineralocorticoid receptors have been developed. In the present study, we have compared the direct activity of spironolactone and four related compounds: prorénone (SC 23133), SC 19886, SC 26304 and its carboxylic analog SC 27169, on aldosterone biosynthesis. Two of them (SC 26304 and its carboxylic analog SC 27169) had no effect on adrenal steroidogenesis, even at concentrations up to 10(-3)M. Spironolactone and prorenone (SC 23133) induced a marked but reversible inhibition of aldosterone biosynthesis. SC 19886 totally inhibited aldosterone production and the activity of this compound lasted for more than 7 hours. In addition, SC 19886 and prorenone (SC 23133) totally suppressed ACTH and angiotensin II-induced stimulation of aldosterone biosynthesis whereas SC 27169 was unable to block adrenal response to these corticotropic hormones. Our results suggest that compounds such as prorenone (SC 23133), SC 19886 and spironolactone, which are potent inhibitors of aldosterone biosynthesis could be more active in the treatment of primary aldosteronism than those antimineralocorticoids which are devoid of action on aldosterone biosynthesis.

Metabolic effects of high dose amiloride and spironolactone: a comparative study in normal subjects

Amiloride (75 mg daily) and spironolactone (300 mg daily) were given to five normal subjects for 7 days in order to compare metabolic effects at maximal doses. Blood pressure, body weight, Na+ and K+ balance, and plasma concentrations of Na+, K+, active and total renin, angiotensin II, aldosterone, 11-deoxycorticosterone (DOC), 18-hydroxydeoxycorticosterone (18-OH DOC), corticosterone (B), 18-hydroxycorticosterone (18-OH B) and cortisol were measured before and on each day of treatment. Natriuresis and K+ retention were significantly greater with amiloride. Plasma K+ increased from 4.1 +/- 0.2 to 4.9 +/- 0.2 mmol/l (mean +/- s.d.) on amiloride and from 4.0 +/- 0.2 to 4.4 +/- 0.2 mmol/l with spironolactone. Stimulation of renin, angiotensin II, aldosterone and 18-OH B occurred with both drugs but was greater with amiloride in each case. A transient decrease in systolic and diastolic blood pressure was observed after 2 days of spironolactone treatment but not with amiloride. The slope of the regression of aldosterone on angiotensin II during spironolactone treatment was less than that with amiloride, consistent with partial blockade of aldosterone synthesis by spironolactone. These data suggest that the maximum metabolic effects of amiloride exceed those of spironolactone.

Effect of spironolactone on electrolytes, renin, ACTH and corticosteroids in the rat

Spironolactone (S), known to act as a mineralocorticoid antagonist, has been shown in some circumstances to inhibit steroid biosynthesis. To investigate these two actions in vivo in the rat, animals fed a normal or low Na+ diet were treated with S for 7 days. In animals fed a normal Na+ diet, urinary and faecal electrolytes, aldosterone and corticosterone excretion were measured daily, plasma renin, aldosterone, corticosterone, ACTH, progesterone, DOC and 18-OH-DOC were determined after 4 and 7 days of treatment. In animals fed a low Na+ diet, urinary electrolytes were measured daily and plasma and urinary aldosterone and corticosterone were determined at intervals during the introduction of the diet and in the course of treatment. On a normal Na+ diet, S induced a slight non significant rise in the urinary Na+/K+ ratio on the first day of treatment, no change in faecal electrolyte excretion, and a sustained increase in aldosterone but not in corticosterone excretion. It produced a 6-fold elevation in plasma aldosterone levels, a less marked rise in renin and progesterone, a delayed increase in DOC and no change in ACTH, 18-OH-DOC or corticosterone concentration. On a low Na+ diet, treatment induced a rise in the urinary Na+/K+ ratio, and in urine and plasma aldosterone levels and no change in corticosterone values. Our results confirm, in the intact rat, the antimineralocorticoid action of S characterized by an increase in Na+ excretion but no change in K+ elimination. No inhibitory effect of spironolactone on aldosterone, corticosterone or 18-OH-DOC biosynthesis could be demonstrated in our experimental model.

The effects of canrenoate K on corticosteroid biosynthesis in nephrectomized dogs

There is evidence from in vitro experiments that spironolactone not only antagonises the peripheral effects of aldosterone but also inhibits the production of corticosteroids by the adrenals. However relevant data from clinical studies are contradictory probably because spironolactone action on the kidneys also activates other mechanisms, such as renin secretion and potassium retention, which are potent stimulants of the adrenal cortex and thus tend to compensate for the inhibition. To determine the inhibitory effect of spironolactone on the adrenals in isolation, three groups of nephrectomized dogs were studied. Steroidogenesis was stimulated either by angiotensin II, potassium, or ACTH infusion. Potassium canrenoate was administered i.v. bolus at the beginning of the experiment. All the groups showed a similar marked decrease in plasma renin activity (PRA). Plasma aldosterone and cortisol were stimulated by the appropriate stimulus but their increase was blunted after the canrenoate K administration. The altered response between the subgroups was statistically significant (P less than 0.05). Plasma progesterone increased after the administration of canrenoate K. The response difference between the respective subgroups was again statistically significant (P less than 0.05). Canrenoate K was rapidly eliminated from the systemic circulation. These data indicate that canrenoate K causes a partial inhibition of aldosterone and cortisol stimulated secretion but augments the plasma levels of the precursor progesterone, as would be expected following inhibition of specific steps of corticosteroid biosynthesis.

The effect of the antimineralocorticoid RU 28318 on aldosterone biosynthesis in vitro

The effect of RU 28318, a specific and highly potent aldosterone antagonist on mineralocorticoid biosynthesis has been studied using a new in vitro model which combined three original features: (1) a very specific radioimmunoassay for aldosterone (2) a simplified perifusion system and (3) frog interrenal tissue which spontaneously produces high amounts of aldosterone. A dose-related inhibition of aldosterone production was observed for doses ranging from 10(-5) to 10(-3) M of RU 28318. The intermediate dose of 10(-4) M caused 71% inhibition of aldosterone production. Long term infusion of RU 28318 for 8 h led to a significant, stable and reversible inhibition of aldosterone production. In addition, we provide evidence that RU 28318 is capable of blocking the stimulation of aldosterone secretion induced by synthetic ACTH or by angiotensin II analogue. The present results demonstrate that RU 28318 is responsible for a significant and reversible inhibition of spontaneous, ACTH-induced and angiotensin II-induced aldosterone biosynthesis in vitro.

Studies of impaired aldosterone response to spironolactone-induced renin and potassium elevations in adenomatous but not hyperplastic primary aldosteronism

Spironolactone (SPL) corrects hypertension, hypokalemia, and hyporeninemia in patients with primary hyperaldosteronism (PHA) by blocking mineralocorticoid (MCH) receptors. We evaluated the effect of continuous SPL treatment (100 to 300 mg/day for 7 days to 9 years) on plasma renin (PRC), potassium, aldosterone (PA), 18-hydroxycorticosterone (18-OHB), deoxycorticosterone (DOC), and corticosterone (B) concentrations and 24-hour urinary excretion of aldosterone (UA) in 24 patients with PHA (15 with an aldosterone-producing adenoma [APA] and nine with idiopathic PHA [IHA]). Despite the normalization of PRC and K in both APA and IHA patients by SPL, UA and PA failed to increase in APA (55.8 +/- 8.8 to 51.4 +/- 7.3 micrograms/24 hr and 54.0 +/- 9.4 to 44.6 +/- 6.2 ng/dl, respectively) in contrast to rises in IHA patients (22.3 +/- 2.5 to 69.3 +/- 10.3 micrograms/24 hr and 16.0 +/- 1.0 to 49.9 +/- 9.9 ng/dl). Similar corrections with amiloride (20-40 mg/day for 2 months) in one patient with APA produced a three- to fourfold increase in UA and PA. In addition, while on SPL the characteristic fall or no change in PA and 18-OHB during upright posture persisted in all APA patients despite further increases in PRC (4.48 +/- 1.15 to 7.86 +/- 1.89) and K (4.0 +/- 0.1 to 4.3 +/- 0.1). The patterns of the aldosterone precursors, DOC, B, and 18-OHB, and their ratios to acute stimulation with cosyntropin were not altered by SPL. Thus, SPL treatment causes a sustained impairment of the aldosterone secretory response to normalized PRC and K, but not to ACTH stimulation, only in patients with APA.

The effects of adrenal and gonadal steroids and K+-canrenoate on the metabolism of aldosterone by rat liver microsomes

The synthesis of polar aldosterone metabolites by rat liver microsomes at physiological concentrations of aldosterone (21.5 nM), was markedly inhibited by progesterone, testosterone, corticosterone, K+-canrenoate and estradiol-17 beta. In contrast, corticosterone and estradiol-17 beta significantly increased the synthesis of reduced aldosterone metabolites by 8- and 15-fold respectively, the majority of which were 5 alpha-reduced products of aldosterone. In experiments at higher substrate (aldosterone) concentrations (20-200 microM) the synthesis of ring A-reduced aldosterone metabolites by liver microsomes followed Michaelis-Menten kinetics with a Km[app] for aldosterone of 160 microM and Vmax[app] of 12.2 nmoles/mg protein/5 min. In these experiments progesterone, testosterone and K+-canrenoate all competitively inhibited the synthesis of reduced metabolites with inhibition constants (Ki [app]) of 70, 85 and 55 microM respectively; however, corticosterone did not. In contrast, estradiol-17 beta increased the rate of synthesis of reduced products by 40%, lowering the Km[app] to 83 microM.

Antiandrogenic properties of spironolactone. Clinical trial in the management of female hirsutism

The effect of spironolactone on female hirsutism was studied in 18 patients. The drug was administered at the dose of 400 mg for the first ten days and 300-200 mg later on in a first group of women (Group A); a second group (Group B) was given 200 mg spironolactone for the whole length of therapy. A significant decrease of the index of Ferriman and Gallwey (p = 0.01) was noted from the 100th day of treatment; acne and seborrhoea improved concomitantly. Plasma total testosterone values fell from 0.64 +/- 0.24 ng/ml to 0.32 +/- 0.12 ng/ml (p = 0.002) during the first 5 days only in the patients of Group A; in the other patients no significant changes were observed. PRL did not significantly change from pretreatment values; FSH and LH values at the 5th, 10th, and 15th day of therapy did not show a uniform course in both groups. On the basis of these results spironolactone administration appears promising in the therapy of female hirsutism.

The role of parmacologic manipulation in adrenal cortical scintigraphy

Adrenal scintigraphy is a unique nuclear medicine procedure that provides noninvasive, functional information concerning the status of the adrenal cortex. The uptake of iodocholesterol, in addition to localizing adrenal cortical abnormalities, can be manipulate to focus on adrenal cortical dysfunction in either the aldosterone, cortisol, or androgenproducing portions of the adrenal cortex. The uptake of iodocholesterol correlates significantly with the abnormal secretion of cortisol in Cushing's syndrome, aldosterone in the model of adrenal zona glomerulosa function, and adrenal androgen secretion in hyperandorgenism. For these reasons, adrenal scintigraphy is an important diagnostic modality in the evaluation of adrenal cortical function.

The metabolism of canrenone in vitro by rat liver preparations

1. The metabolism of [1-3H]canrenone, a primary metabolite of spironolactone and potassium canrenoate, by rat liver preparations in vitro has been investigated. 2. Canrenone was metabolized by 3-oxo-delta 4-reduction to give 3 alpha-hydroxy-5 beta-spirolactones, and also by a number of O2 and NADPH-dependent microsomal hydroxylation reactions. 3. A major metabolic route requiring the presence of a microsomal fraction, but apparently independent of oxygen and NADPH, led to the formation of a number of compounds tentatively identified as trihydroxy-spirolactones.

Long term spironolactone and the adrenal cortex in essential hypertension

In view of recent evidence that spironolactone may inhibit synthesis of corticosteroids by a direct effect on the adrenal cortex, adrenocortical function was studied in eight patients with essential hypertension who had been treated with spironolactone from 3 months to 14 years. Their 24 h renal excretion of adrenocorticoid metabolites and the responses of cortisol, aldosterone and 18-hydroxy-11 -deoxycorticosterone (18-OH-DOC) to an incremental infusion of tetracosactrin (1-24 ACTH) were compared with those in eight patients with recently diagnosed essential hypertension who had received no spironolactone. The spironolactone-treated group had a significantly higher excretion of aldosterone, whilst the excretion of other adrenocorticoid metabolites did not differ. The same group also required less tetracosactrin to stimulate a detectable rise of plasma cortisol and 18-OH-DOC, they had greater plasma 18-OH-DOC responses at all infusion rates and, at the lowest infusion rates, had greater aldosterone responses. These results indicate that long-term spironolactone therapy does not inhibit adrenocortical function and may have some stimulatory effects.

Danazol inhibits human adrenal 21-and 11 beta-hydroxylation in vitro

The effects of danazol on steroidogenesis in vitro in the 16-20 week old human fetal adrenal were examined by studying: 1) danazol binding to adrenal microsomal and mitochondrial cytochrome P-450, and 2) enzyme kinetics of danazol inhibition of the adrenal microsomal 21-hydroxylase and the mitochondrial 11 beta-hydroxylase. The addition of danazol to preparations of adrenal microsomes or mitochondria elicited a type I cytochrome P-450 binding spectrum. Danazol bound to microsomal cytochrome P-450 binding spectrum. Danazol bound to microsomal cytochrome P-450 with a high affinity apparent spectral dissociation constant (KS) of 1 microM and with a lower affinity K's of 10 microM. Danazol bound to mitochondrial cytochrome P-450 with a KS of 5 microM. In addition, danazol competitively inhibited the microsomal 21-hydroxylase (apparent enzymatic inhibition constant KI = 0.8 microM) and the mitochondrial 11 beta-hydroxylase (KI = 3 microM). These findings demonstrate that low concentrations of danazol directly inhibit steroidogenesis in the human fetal adrenal in vitro.

Comparative effects of canrenoate-K and prorenoate-K upon aldosterone biosynthesis in perifused frog interrenal glands

To investigate the possible direct effect of two aldosterone antagonists (Canrenoate-K and Prorenoate-K) upon mineralocorticoid biosynthesis a perifusion system technique has been developed. Frog interrenal tissue was selected for its ability to secrete huge amounts of aldosterone (twice as much as corticosterone in resting conditions). Throughout the experiment, secretion of aldosterone was measured every ten minutes by means of a sensitive and highly specific radioimmunoassay method. Increasing concentrations of both Canrenoate-K and Prorenoate-K (ranging from 10(-4)M to 10(-3)M) caused a dose-related inhibition of aldosterone output. At a dose of 3.16 x 10(-4)M, Prorenoate-K appeared to be somewhat more potent (57.8% inhibition) than Canrenoate-K (47.8% inhibition). Infusion of both Canrenoate-K and Prorenoate-K at a dose of 5 x 10(-4)M during 1 or 2 hours induced a similar sharp decrease in mineralocorticoid secretion. Thus, it appears that Canrenoate-K and Prorenoate-K beside their well known effects at renal tubular receptor sites do also inhibit aldosterone biosynthesis. These results indicate that in vivo administration of aldosterone antagonists may first involve a transient decrease in aldosterone secretion. Furthermore, they suggest that mineralocorticoid biosynthesis might be regulated by a short loop feedback mechanism.

Adrenal hydroxylations in genetically obese and hypertensive rats

The separate steps in the formation of aldosterone from cholesterol were studied in a strain of spontaneously hypertensive rats in which phenotypic obesity is inherited as a recessive trait (Koletsky rats). The obese and hypertensive state had little or no effect on side-chain cleavage of cholesterol, formation of progesterone from pregnenolone or 21-hydroxylation. Mitochondrial 18-hydroxylation of endogenous and exogenous corticosterone, however, as well as 18- and 11 beta-hydroxylation of deoxycorticosterone, were increased in obese hypertensive rats, both when compared with non-obese hypertensive siblings and when compared with healthy Sprague-Dawley rats. 18-Hydroxylation of corticosterone was increased more than 18-hydroxylation of deoxycorticosterone. In non-obese hypertensive rats, the adrenal content of mitochondrial cytochrome P-450 was lower than that in obese hypertensive rats but higher than that in rats of the conventional Sprague-Dawley strain. The results are discussed with respect to possible heterogeneity of adrenal cytochrome P-450 and to possible explanations for the changes observed.

A comparison of some extra-renal effects of spironolactone and canrenone

1 Measurement of changes in trans-mural rectal potential difference (t.m.r.p.d.) and plasma aldosterone levels have been used in a comparison of the extra-renal activities of spironolactone and its major metabolite canrenone. 2 A characteristic pressure artifact was observed during measurement of t.m.r.p.d. When pressure artifacts were eliminated, there was a log-linear relationship between increasing doses of intravenous aldosterone and maximum increase in t.m.r.p.d. 3 Pre-treatment for 5 days with spironolactone or canrenone produced a similar attenuation of the increase in t.m.r.p.d. produced by infused aldosterone, suggesting that canrenone is the active metabolite of spironolactone in the rectum. This is in contrast to the significantly greater renal activity of spironolactone that has been demonstrated after a similar treatment period. Neither antagonist treatment produced significant changes in pre-infusion plasma aldosterone concentrations. 4 The need for assay of the extra-renal activities of aldosterone antagonists in the assessment of their therapeutic potential is discussed.

The effect of the administration of spironolactone on the concentration of plasma testosterone, estradiol and cortisol in male dogs (1)

The effect of the administration of spironolactone, deacetylspironolactone, aldadiene or soldactone on the concentration of plasma testosterone, estradiol, and cortisol was examined in male dogs. Decreases of 60 to 75% in plasma testosterone and estrodiol occur only at high doses (100 mg/kg) of spironolactone or deacetylspironolactone but not at low doses of spironolactone (5 to 10 mg/kg); they occur concomitantly with similar decreases of androgen formation by the testis. No decreases were detected with aldadiene or soldactone. Treatment of dogs with spironolactone (100 mg/kg) also lowered by 50 to 65% the concentration of cortisol in adrenal venous plasma.

Non-interaction of spironolactone medication and cortisol metabolism in man

In 5 healthy subjects and in 5 patients with decompensated liver diseases, the concentrations of cortisol, canrenone and canrenoate-K were determined after single doses and after a long-term treatment with spironolactone. The concentrations of the metabolites of spironolactone were determined fluorimetrically, those of cortisol by a highly specific radioimmunoassay with previous chromatographic separation. As a result, non-interaction between spironolactone medication and cortisol metabolism, even at high dose and long-term treatment conditions, was established neither in normal test subjects nor in patients with liver failure.