[Arguments for the existence of an endogenous inhibitor of renal Na-K ATPase with steroid structure and natriuretic action]. / Arguments en faveur de l'existence d'un inhibiteur endogène de la Na-K ATPase rénale, de nature stéroïdienne et à vertu natriurétique.

In order to explain the opposite effect of 6,7-dihydroxylated isomers of 6, 7 - dihydrocanrenone on the urinary sodium and potassium excretion, we have tested the effect of these substances isolated from human urine on the Na(+)-K+ pump from different tissue preparation: rabbit kidney slices as well as NA-K ATPase purified from the kidney. Our results show an inhibition of pump as well as enzyme activity by the 6 beta 7 alpha isomer while the 2 other isomers are either uneffective or slightly stimulating. The 6 beta 7 alpha dihydroxy-6, 7-dihydrocanrenone could be one of the plasma ouabain-like substance incriminated in the pathogenesis of volume-expanded hypertension.

Effect of various 6-dehydro-corticosteroids, 9, 11-dehydro-DOCA and 9 alpha-fluoro-DOCA on the fluxes of sodium and potassium.

The introduction of a double bond at carbons 6 and 7 (6-dehydro-derivatives) of deoxycorticosterone acetate (DOCA), cortisol-21-acetate, 9 alpha-fluorocortisol-21-acetate (9 alpha-F-C-ac) and aldosterone-21-acetate substantially reduces affinity for Type II receptors but not for Type I receptors. Such a modification changes the effect of these steroids on urinary excretion of Na+ and K+. 6-Dehydro-derivatives will thus bind preferentially to receptor Type I inducing the retention of sodium and compete with mineralocorticoids for such receptors. The increase in both natriuresis and kaliuresis when corticosteroids and their 6-dehydro-derivatives are administered together may be interpreted as evidence for a Type II receptor mediation of those ion fluxes. The ionic changes are not mediated by the (Na+ + K+)-ATPase system. The fluoration at 9 and the dehydrogenation at C9C11 of DOCA result in a strong increase of binding to Type I receptor and of sodium retention.

Identification of biologically active natural spirolactone derivatives in man and animal.

For the first time, the presence of three natural spirolactones hydroxylated at C6C7 (6 alpha, 7 alpha-, 6 beta, 7 alpha- and 6 beta, 7 beta-dihydroxy-6,7-dihydrocanrenone (DHC) is demonstrated in man and in animal urine (rat, dog, sheep), and possibly in the blood. The existence of the fourth isomer 6 alpha, 7 beta- is also possible. Salt-loading in man and the rat results in a decrease in urinary 6 alpha, 7 alpha- and 6 beta, 7 beta-DHC. Salt-depletion increases their urinary concentration in the rat. DHC isomers are not found in the urine of adrenalectomized rats. Injected into the caudal vein of the rat, both 6 alpha, 7 alpha- and 6 beta, 7 beta-DHC induce a significant retention of Na+. On the other hand, 6 beta, 7 alpha-DHC significantly increases Na+ and K+ excretion. The biological activities of these natural compounds seem to be different from those of synthetic spirolactonic drugs.

Effect of 6-dehydro-DOCA and 6-dehydro-9 alpha-fluorocortisol acetate on the excretion of sodium and potassium in the rat.

Deoxycorticosterone acetate (DOCA) and 9 alpha-fluorocortisol acetate (9 alpha-F-Cac) can be modified by the introduction of a double bond at carbons 6 and 7 (6-dehydro-derivatives). Such a modification markedly changes the effect of the steroids on urinary excretion of Na+ and K+. Since 6-7 reduction of DOCA and 9 alpha-F-Cac substantially reduces affinity for Type II receptors but not Type I receptors, 6-dehydro-derivatives will thus bind preferentially to receptors influencing the retention of sodium (the "mineralocorticoid" or Type I receptor), and compete with mineralocorticoids for such receptors. We interpret the increase in both natriuresis and kaliuresis when mineralocorticoids and their dehydro-derivatives are administered together as evidence for a Type II receptor mediation of these ion fluxes.

Discovery of a natural spirolactone derivative in man and animal.

The presence of 6,7-dihydroxy-6,7-dihydrocanrenone (DHC) in man and in animal has been shown. Sodium loading results in a decrease of urinary DHC. On the contrary, sodium depletion increases its concentration.

Role of hydrophobic effects and polar groups in steroid-mineralocorticoid receptor interactions.

To test whether hydrophobic interactions are the main driving forces in the association of steroids with mineralocorticoid receptors, the binding free energy calculated (delta Gc) using the surface area of the steroids accessible to water was compared with the observed free energy (delta GM) obtained from the Kd at the equilibrium estimated in the rat cytosol. The results are consistent with a binding process involving principally hydrophobic effects implying association of both faces of the steroid with the receptor. The discrepancies between calculated and observed values probably depend upon the mechanism of hydrogen bonding of the polar groups of the steroids to those on the receptor. Hydrogen bonds in an aqueous environment are likely between polar groups of the receptor and the 21-OH, 18-OH and 11-18 hemiacetal oxygen of the steroids. Strong hydrogen bonding in a hydrophobic environment from the 3-CO and 20-CO groups is a possibility (the latter with a dihedral angle C16-C17-C20-O20 of approximately equal to 7 degrees). Such a strong hydrogen bond from the 9 alpha-fluorine atom could account for the observed high affinity receptor binding of 9 alpha-fluorocortisol and 9 alpha-fluoroprednisolone. The loss of affinity in 11-deoxycortisol and cortisol may be explained by modification of the C17 side chain and repulsion forces from the 11 beta-OH.

[Steroid ligands of androgen binding protein. The enantiomers of trans-trans and cis-trans perhydrohexestrols and trans-trans perhydrodiketones]. / Sur les ligands stéroïdoïdes de l'androgen binding protein,. Les énantiomères des trans-trans et cis-trans perhydrohexestrols et trans-trans perhydrodicétones.

In the framework of a study on nonsteroidal androgens, the authors previously observed that in perhydrohexestrol series, the (+/-)-[(cis-4 hydroxycyclohexyl)-4(trans-4 hydroxycyclohexyl)-hexane] or cis-trans perhydrohexestrol and especially the (+/-)-(3,4 bis (trans-4-oxocyclohexyl)-hexane) or trans-trans perhydrodiketone, there is no affinity for AR (androgen receptor of the prostate) but they bind with high and specific affinity to the testosterone binding sites on ABP (epididymal androgen-binding protein). In this work, we describe the preparation, the stereochemistry and biological activities of trans-trans and cis-trans perhydrohexestrols and of trans-trans perhydrodiketone as well as their corresponding enantiomers. Biologically the tests AR and ABP are negative for the trans-trans perhydrohexestrol and of trans-trans perhydrodiketone and for its enantiomers. However for the enantiomers of cis-trans perhydrohexestrol and of trans-trans perhydrodiketone, the affinity of the (+) enantiomer for ABP is superior to that of the racemic and that of the (-) enantiomer, whereas the affinity for AR are zero. Chemically, the stereochemistry of the three racemics has been established by X-ray crystallographic analysis or by 1H n.m.r. The n.m.r. spectra have been analyzed in terms of chemical shifts and coupling constants.

Diurnal 18-hydroxy-11-deoxycorticosterone pattern in human stable hypertension.

Diurnal 18-hydroxy-11-deoxycorticosterone (18-OH-DOC) pattern was studied with RIA technique in 33 hypertensive patients in supine position and on normal sodium diet. The compound was evaluated every 2 h from 0800-2000 h. Simultaneously, plasma aldosterone and cortisol were measured. Abnormal 18-OH-DOC behavior was observed in only 2 out of 4 patients with Cushing's disease, while sporadic and slight elevations, synchronous with F, were seen in 5 out of 24 stable essential hypertensive patients [1 with normal plasma renin activity (PRA), 1 with low PRA, and 3 with high PRA]. 18-OH-DOC was normal in 2 cases of hypertension due to renal artery stenosis, in 1 patient with nephrosclerosis, and in 1 patient with horseshoe kidney. From these results, 18-OH-DOC does not seem to play an important pathogenetic role in stable essential hypertension, considering also the low mineralocorticoid activity of the compound.

24 hour profile of 18-hydroxy-11-deoxycorticosterone in normal supine man: relationship with cortisol and aldosterone.

Daily profiles of plasma 18-hydroxy-11-deoxycorticosterone (18-OH-DOC) were studied in four normal supine men on a normal sodium intake. Blood was taken every hour from 01.00 to 24.00 hours. Plasma cortisol (F) and aldosterone (A) were determined hourly for comparative studies. 18-OH-DOC fluctuated considerably during the 24 h period of investigation, the highest values being found during the early morning hours in synchrony with F. The episodic secretions of 18-OH-DOC were also significantly correlated with those of A, which in turn paralleled those of F. We conclude that ACTH, plays a definite role in the regulation of 18-OH-DOC in normal supine men on a normal sodium diet.

Radioimmunoassay for aldosterone and deoxycorticosterone in human plasma. Comparison of various antisera and determination of normal values.

This paper describes a study of the physico-chemical and radioimmunological properties of three antialdosterone antisera which permitted practical conclusions to be drawn. By its high degree of specificity, anti-aldo-3-oxime-BSA constitutes the most useful antiserum for the clinical assay of aldosterone. The principal advantage of this antiserum is that it allows both urinary and blood aldosterone radioimmunoassay without the necessity of including a chromatographic step. No problems arise with the blanks. This work also includes the study of two anti-deoxycorticosterone antisera. The aldosterone and deoxycorticosterone values, obtained from normal subjects under various physiological conditions, are in agreement with the values given in the literature.

18-hydroxylated steroids in human hypertension - clinical study.

The detection of two unknown urinary steroids called x and y in various patients was previously reported. Compound x was tentatively characterized as a derivative of dihydro-18-hydroxy-DOC with two additional polar groups. In this communication clinical observations of a set of 25 hypertensive patients are presented. Compound x alone was found in 4 cases, compound y alone 4 cases and both compound x and y in 5 cases. In several other cases, hypokalemia and/or a decreased urinary Na+/K+ ratio were found.

Mineralocorticoid like effect of new 18-hydroxy-steroid isolated from urine of hypertensive patients.

The affinity of new urinary 18-hydroxy-steroid (Cp x) for mineralocorticoid receptors was estimated. When rat kidney slices were incubated with 2 x 10(-9) M 3H-aldosterone, Cp x (2 x 10(-5) M) was able to compete with aldosterone for the mineralocorticoid cytosol receptors. Cp x had low but significant affinity for mineralocorticoid receptor sites. This affinity was less than that obtained with 18-OH-progesterone. Moreover, in the adrenalectomized rats, the injection of Cp x induced a decrease of urinary Na+/K+ ratio which seems comparable to that obtained with 18-OH-progesterone.