Aldosterone Increases Vascular Permeability in Rat Skin.

The aim of this study was to evaluate the effect of acute aldosterone (ALDO) administration on the vascular permeability of skin. ALDO was injected intradermally into rats, and vascular permeability was measured. Eplerenone (EPL), a selective mineralocorticoid receptor (MR) antagonist, was used. Skin biopsies were carried out for immunohistochemical (IHC) staining, and polymerase chain reactions were performed to analyze the expression of MR, 11ß-hydroxysteroid dehydrogenase type 2, von Willebrand factor (vWF), vascular endothelial growth factor (VEGF), and zonula occludens 1. Our study showed the presence of MR in the rat skin vasculature for the first time. It was found that ALDO injection resulted in a more than 30% increase in vascular permeability and enhanced the endothelial exocytosis of vWF. The effect of ALDO diminished after EPL administration. An accumulation of vWF and a reduction in VEGF IHC staining were observed following chronic EPL administration. No effect of ALDO or EPL on the mRNA expression of the studied genes or skin structure was observed. The results suggest that ALDO increases vascular permeability in the skin via an MR-dependent mechanism. This effect of ALDO on skin microcirculation may have important therapeutic implications for diseases characterized by increased levels of ALDO and coexisting skin microangiopathy.

Critical role of the mineralocorticoid receptor in aldosterone-dependent and aldosterone-independent regulation of ENaC in the distal nephron.

The epithelial Na+ channel (ENaC) constitutes the rate-limiting step for Na+ absorption in the aldosterone-sensitive distal nephron (ASDN) comprising the late distal convoluted tubule (DCT2), connecting tubule (CNT), and collecting duct (CD). Previously, we demonstrated that ENaC activity in the DCT2/CNT transition zone is constitutively high and independent of aldosterone, in contrast to its aldosterone dependence in the late CNT/initial cortical CD (CCD). The mineralocorticoid receptor (MR) is expressed in the entire ASDN. Its activation by glucocorticoids is prevented through 11ß-hydroxysteroid dehydrogenase 2 (11ß-HSD2) abundantly expressed in the late but probably not early part of the ASDN. We hypothesized that ENaC function in the early part of the ASDN is aldosterone independent but may depend on MR activated by glucocorticoids due to low 11ß-HSD2 abundance. To test this hypothesis, we used doxycycline-inducible nephron-specific MR-deficient [MR knockout (KO)] mice. Whole cell ENaC currents were investigated in isolated nephron fragments from the DCT2/CNT or CNT/CCD transition zones using the patch-clamp technique. ENaC activity was detectable in the CNT/CCD of control mice but absent or barely detectable in the majority of CNT/CCD preparations from MR KO mice. Importantly, ENaC currents in the DCT2/CNT were greatly reduced in MR KO mice compared with ENaC currents in the DCT2/CNT of control mice. Immunofluorescence for 11ß-HSD2 was abundant in the CCD, less prominent in the CNT, and very low in the DCT2. We conclude that MR is critically important for maintaining aldosterone-independent ENaC activity in the DCT2/CNT. Aldosterone-independent MR activation is probably mediated by glucocorticoids due to low expression of 11ß-HSD2.NEW & NOTEWORTHY Using a mouse model with inducible nephron-specific mineralocorticoid receptor (MR) deficiency, we demonstrated that MR is not only critical for maintaining aldosterone-dependent ENaC activity in CNT/CCD but also for aldosterone-independent ENaC activity in DCT2/CNT. Furthermore, we demonstrated that cells of this latter nephron segment express little 11ß-HSD2, which probably allows glucocorticoids to stimulate MR, resulting in aldosterone-independent ENaC activity in DCT2/CNT. This site-specific ENaC regulation has physiologically relevant implications for renal sodium and potassium homeostasis.

Mineralocorticoid receptor antagonists-pharmacodynamics and pharmacokinetic differences.

Mineralocorticoid receptor antagonists (MRAs) are best known as potassium-sparing diuretics due to their blockade of aldosterone action in renal epithelial tissues. They are also beneficial for the treatment of heart failure, primarily due to effects in non-epithelial tissues. Currently there are only two steroidal MRAs that have been approved for use; spironolactone (and its active metabolite canrenone) and eplerenone. However, the search is on for novel generations of MRAs with increased potency and tissue selectivity. A number of novel non-steroidal compounds are in preclinical and early development, with one agent moving to phase III trials. The development of these agents and the mechanisms for their pharmacologic superiority compared to earlier generations of MRAs will be discussed in this review.

Papel de la aldosterona en las alteraciones vasculares funcionales y en el proceso inflamatorio asociados a la hipertensión en ratas / Role of aldosterone in vascular functional alterations and the inflammatory process associated to hypertension in rats

Objetivos: Estudiar la participación de la aldosterona en la disfunción vascular, el proceso inflamatorio y estrés oxidativo vascular asociado a hipertensión. Material y método: Se utilizaron ratas (n = 16) espontáneamente hipertensas (SHR) de 22 semanas de edad. La mitad de las ratas fueron tratadas durante 10 semanas con eplerenona a una dosis de 30 mg/kg/día (E-30). Se utilizaron ratas (n = 8) normotensas (WKY) como grupo de referencia. La presión arterial se midió de manera indirecta en la arteria caudal de la cola de las ratas. Al final del tratamiento las ratas se sacrificaron y se pesaron los corazones. Se evaluó la función endotelial en anillos aórticos en respuesta a la acetilcolina. La expresión del ARN mensajero (ARNm) de las interleucinas 1 β y 6 (IL-1β e IL-6), del factor de necrosis tumoral α (TNF-α), de la enzima óxido nítrico endotelial (eNOS) y de la subunidad p22phox de la enzima NAD(P)H oxidasa se midió en la aorta de las ratas. Resultados: Las SHR presentaron unos valores de presión arterial sistólica mayores (p < 0,05) que las ratas controles WKY (199,8±4,2 frente a 125,3±2,0 mmHg). El tratamiento con eplerenona redujo (p < 0,05) ligeramente las cifras de presión arterial en las ratas hipertensas (E30; 181,0±2,0 mmHg). No hubo diferencias en el peso corporal de las ratas, sin embargo el peso relativo del corazón de las ratas hipertensas era significativamente mayor respecto a las ratas normotensas y se normalizó con el tratamiento con eplerenona. La relajación a acetilcolina estaba significativamente reducida en las ratas SHR así como la expresión vascular de la eNOS. Sin embargo, las ratas hipertensas presentaron una sobreexpresión vascular del ARNm de IL-1β, IL-6, TNF-α y p22phox respecto a las WKY (p < 0,05). El tratamiento con eplerenona normalizó la función endotelial en las ratas hipertensas; aumento la expresión del ARNm de eNOS y redujo la expresión vascular de las citocinas IL-1β, IL-6, TNF-α, así como de la p22phox. Conclusiones: La aldosterona participa en las alteraciones funcionales vasculares en las SHR reduciendo la biodisponibilidad de óxido nítrico, aumentando el estrés oxidativo y el proceso inflamatorio vascular(AU)

Objetives: To study the participation of aldosterone in the vascular dysfunction, inflammatory process and vascular oxidative stress associated to hypertension. Material and methods: Half of the group of 22 week-old spontaneously hypertensive rats (n=16) were treated with eplerenone (E-30; 30 mg/kg/day) for 10 weeks. Normotensive rats (WKY; n = 8) were used as reference group. Systolic arterial pressure (SAP) was measured by the tail-cuff method. Body weight and heart weight were measured at the end of the treatment. Endothelium-dependent relaxations, as well as vascular mRNA expression of interleukin 1 β and 6 (IL-1β and IL-6), tumor necrosis factor alpha (TNF-α), of endothelial nitric oxide synthase (eNOS), NAD(P)H oxidase subunit p22phox were studied in aorta from SHR untreated or treated with eplerenone. Results: SHR showed higher levels of systolic blood pressure (p < 0.05) as compare with control rats (199.8±4.2 vs. 125.33±2.0 mmHg). Although there were no differences in the body weight among the groups, hypertensive rats had a higher relative heart weight compare to normotensive rats and it was normalize with the treatment of eplerenone (p < 0.05). SHR showed higher vascular mRNA expression of IL-1β, IL-6, TNF-α and p22phox compared to WKY (p < 0.05). Treatment with eplerenone slightly reduced (p < 0.05) blood pressure in hypertensive rats (E30; 181.0±2.0 mmHg) and normalized acetylcholine relaxations. Eplerenone enhanced (p < 0.05) eNOS and reduced p22phox, IL-1β, IL-6, TNF-α of aortic mRNA expressions in SHR. Conclusions: In SHR, aldosterone participates in the functional vascular alterations through the diminution of nitric oxide availability and the enhancement of the inflammatory process and the increase of vascular oxidative stress(AU)

Towards a correlation between drug properties and in vitro transdermal flux variability.

Over recent years, there has been growing evidence that the permeability coefficient variability describing any specific transdermal drug delivery system is not always normally distributed. However, since different researchers have used different test compounds, methodologies and skin types, it has been difficult to identify any general correlation between drug properties and flux variability. The aim of the present study was to investigate whether there was a relationship between these two variables. To this end, six different compounds (sucrose, adenosine, aldosterone, corticosterone, oestradiol and testosterone) exhibiting a range of partition coefficients but relatively similar molecular weights were screened by taking multiple replicate measurements of their permeation profiles as they penetrated across porcine skin in vitro. It was found that for relatively hydrophilic solutes (log P(o/w)< or = approximately 2.5), physicochemical properties that facilitated slow transdermal flux were associated with more positively skewed permeability coefficient distributions while rapid flux was associated with more symmetric distributions. However, no correlation could be found between molecular properties and the extent of statistical fit to either the normal or log-normal distribution.

Use of steroid profiles in determining the cause of adrenal insufficiency.

HYPOTHESIS: A cortisol response to adrenocorticotropin injection is the standard test for diagnosing adrenal insufficiency. Multiple steroid hormones can now be accurately measured by tandem mass spectrometry in a single sample. The study objective was to determine whether a steroid profile, created by simultaneous measurement of 10 steroid hormones by tandem mass spectrometry, would help determine the cause of adrenal insufficiency. DESIGN: A 10-steroid profile was measured by tandem mass spectrometry during the performance of a standard high dose cortrosyn stimulation test. The steroids were measured at baseline, 30, and 60min following synthetic adrenocorticotropin injection. Adrenal insufficiency was defined as a peak cortisol level of less than 20microg/dL. Testing was conducted in the general clinical research center of a university medical center. Normal volunteers, patients suspected of having adrenal insufficiency, and patients with known adrenal insufficiency participated. RESULTS: Our results showed that adrenal insufficiency of any cause was adequately diagnosed using the response of 11-deoxycortisol, dehydroepiandrosterone, or these analytes combined in a two-steroid profile. A three-steroid profile yielded a test with 100% accuracy for discriminating primary adrenal insufficiency from normal status. Primary adrenal insufficiency was well separated from secondary adrenal insufficiency using only a single aldosterone value. 11-Deoxycortisol, dehydroepiandrosterone, and a two-steroid profile each provided fair discrimination between secondary adrenal insufficiency and normal status. CONCLUSIONS: We conclude that stimulated levels of aldosterone, 11-deoxycortisol, dehydroepiandrosterone, and a two- or three-steroid profile provided additional discrimination between states of adrenal sufficiency and insufficiency. It is proposed that a steroid profile measuring cortisol, aldosterone, 11-deoxycortisol, and dehydroepiandrosterone would potentially improve the ability to determine the cause of adrenal insufficiency.

Cardioprotective effects of eplerenone in the rat heart: interaction with locally synthesized or blood-derived aldosterone?

Mineralocorticoid receptor antagonism with eplerenone reduces mortality in heart failure, possibly because of blockade of the deleterious effects of aldosterone. To investigate these effects, rat Langendorff hearts were exposed to aldosterone and/or eplerenone. Under normal conditions, aldosterone increased left ventricular pressure and decreased coronary flow. Eplerenone did not block these effects. Eplerenone reduced infarct size (from 68+/-2% to 53+/-4%; P<0.05) and increased left ventricular pressure recovery (from 44+/-2% to 60+/-5%; P<0.05) after 45 minutes of coronary artery occlusion and 3 hours of reperfusion, whereas aldosterone did not affect these parameters. To verify the origin of cardiac aldosterone, hearts were perfused with 3 to 30 nmol/L aldosterone and either frozen immediately or exposed to washout. Without washout, cardiac aldosterone was 1.5 times aldosterone in coronary effluent (CE), that is, too high to be explained on the basis of its presence in extracellular fluid. The cardiac levels of aldosterone correlated with its CE levels (r=0.81; P<0.01), and both were unaffected by eplerenone. During washout, tissue aldosterone disappeared monophasically (half life, 9+/-1 minutes), and CE aldosterone disappeared biphasically (half life 1+/-0 and 8+/-1 minutes, respectively). During buffer perfusion, cardiac aldosterone was at or below the detection limit. In conclusion, eplerenone improves the condition of the heart after ischemia and reperfusion. This does not relate to interference with the inotropic and vasoconstrictor effects of aldosterone. The majority of cardiac aldosterone, if not all, is derived from the circulation. The rapid, mineralocorticoid receptor-independent kinetics of aldosterone suggest that its accumulation in the heart involves cell surface binding rather than internalization.

P-glycoprotein modulates aldosterone plasma disposition and tissue uptake.

Aldosterone plays an important role in the pathophysiology of numerous cardiovascular disorders including heart failure and hypertension. Because aldosterone's actions are primarily mediated by its interaction with an intracellular mineralocorticoid receptor, factors affecting the cellular uptake and distribution of aldosterone may be important determinants of the hormone's activity. P-glycoprotein (P-gp) is an ATP-binding cassette efflux transporter encoded by the ABCB1 (also known as MDR1) gene in humans. P-gp is expressed on the luminal membrane of the capillary endothelial cells of tissues that are targets for aldosterone, including the brain and heart, where it attenuates cellular uptake of substrates. Recent in vitro evidence indicates P-gp transports aldosterone. Therefore, in this study we tested the hypothesis that P-gp modulates the uptake of aldosterone into the brain and heart by comparing the plasma and tissue distribution of [3H]-aldosterone in wild-type and P-gp-deficient [mdr1a/1b (-/-)] mice. Compared with wild-type mice, [3H]-aldosterone activity in the plasma, brain, and heart was significantly (P < 0.05) higher in the mdr1a/1b (-/-) animals. The area under the plasma or tissue concentration-time curves in the mdr1a/1b (-/-) mice was 2.0, 1.6, and 1.6-fold higher in the brain, heart, and plasma, respectively, than in wild-type controls. Our results demonstrate that P-gp plays an important role in aldosterone plasma disposition and modestly limits its uptake into the brain. The increased exposure of the brain and heart to aldosterone in the absence of P-gp suggests P-gp may play a key role in modulating aldosterone's effects in these organs.

Overexpression of the mineralocorticoid receptor protects against injury in PC12 cells.

Mineralocorticoid receptor expression is increased following neuronal injury, and this is associated with increased neuronal survival. Here we demonstrate a causal link between overexpression of MR in PC12 cells and protection against death induced by staurosporine and oxygen-glucose deprivation. This survival effect is abrogated by MR antagonism. Drugs which upregulate MR may form the basis for a novel therapeutic approach in conditions such as stroke and head injury.

Especificidad de acción de la aldosterona e hipertensión arterial / Specificity of the action of aldosterone and arterial hypertension

La enzima 11 beta-hidroxiesteroide deshidrogenasa tipo 2 (11 HSD2) confiere la especificidad de la acción de la aldosterona respecto a otros corticoides circulantes (cortisol) en los tejidos que deben responder de forma específica a los mineralocorticoides. Esta especificidad debe darse sobre todo en ciertos epitelios transportadores de sodio como el túbulo distal del riñón y en el colon. Esta enzima, poco conocida hasta hace unos años, se está revelando como de gran importancia, ya que interviene en la regulación de la presión arterial. En primer lugar, mutaciones del gen que codifica la enzima causan una forma rara de hipertensión sal sensible de herencia mendeliana autosómica recesiva conocida como exceso aparente de mineralocorticoides (AME). En segundo lugar, se ha determinado que en la población normal, polimorfismos genéticos en 11 HSD2 se asocian con una reducción de la actividad de la enzima in vivo. Esta reducción de la actividad enzimática así como los polimorfismos genéticos que la determinan se han relacionado con un incremento de la respuesta presora a la ingestión elevada de sal, fenómeno conocido como sensibilidad a la sal, tanto en sujetos sanos como en pacientes con hipertensión arterial esencial. Por tanto, es un gen candidato que intervendría en la patogenia de la hipertensión arterial (HTA) "esencial", sobre todo sensible a la sal y que debe aún ser estudiado en mayor profundidad (AU)

Penetration of endogenous steroid hormones corticosterone, cortisol, aldosterone and progesterone into the brain is enhanced in mice deficient for both mdr1a and mdr1b P-glycoproteins.

Numerous investigations have confirmed an important role for multidrug-resistance gene 1-type P-glycoproteins (MDR1-type P-gps) in the blood-brain barrier, protecting the brain against the accumulation of a wide range of toxic xenobiotics and drugs. Several studies have provided evidence in vitro that certain steroid hormones are transported by MDR1-type P-gps; however, the question of whether this might also apply to the situation in vivo still remained to be determined. We used mice deficient for both murine mdr1a and mdr1b P-gps [mdr1a/1b(-/-)] to determine the uptake of [3H]-cortisol, [3H]-corticosterone, [3H]-aldosterone and [3H]-progesterone into the plasma, brain, testes, liver, spleen, pituitary and adrenal glands. We provide evidence that the access of the endogenous steroid hormones corticosterone, cortisol and aldosterone is regulated by MDR1-type P-gps in vivo. As peripherally administered steroid hormones accumulate in the brain of mice deficient for MDR1-type P-gps, mdr1a/1b proteins are likely to transport these hormones out of the brain, providing a kinetic barrier to their entry. Intracerebral progesterone concentrations are influenced by MDR1-type P-gp function as well; however, the effects are only small. In addition, all four endogenous glucocorticoid hormones accumulated in the testes of mdr1a/1b(-/-) mice. Our findings underline the importance of MDR1-type P-gps as an endogenous barrier system controlling the access of endogenous steroid hormones at the blood-brain barrier to maintain homeostatic control and to protect central nervous system neurones.

Short term cardiovascular effects of aldosterone in healthy male volunteers.

Clinical evidence of rapid, nongenomic aldosterone effects in the cardiovascular system has been provided by clinical studies; an increase in systemic vascular resistance (SVR) was shown by invasive techniques within 3 min after injection of aldosterone. Here, we study the dose dependency and the later course of the rapid aldosterone effects by noninvasive techniques. In 12 healthy male volunteers, SVR and heart rate variability were determined by impedance cardiography and digital electrocardiography, respectively, for 8 h after the injection of 0.05 or 0.5 mg aldosterone in a double blind, placebo-controlled, 3-fold cross-over study. No significant differences were observed for baseline values among the three treatments. The area under the curve of SVR during the first 45 min after injection was significantly different between the periods with the highest areas under the curve seen after the injection of 0.5 mg aldosterone (mean +/- SD, 40.4 +/- 12.8 vs. 36.8 +/- 10.3 for 0.05 mg aldosterone and 36.8 +/- 10.4 for placebo; P = 0.05). Individual comparisons showed significant differences at 6 and 30 min between placebo and the 0.5 mg aldosterone period (P < 0.05), with values for the 0.05 mg aldosterone period similar to those for the placebo period. From 330-390 min, opposite changes occurred; SVR was depressed during the 0.05 mg (P < 0.05) and 0.5 mg aldosterone periods compared with that during the placebo period. These delayed effects may reflect an increased vagal tone in the aldosterone groups, as demonstrated by higher values of the time domain parameter of heart rate variability pNN50. This study provides further evidence for clinically detectable rapid cardiovascular aldosterone effects in vivo obtained by noninvasive techniques. The data are consistent with the view of aldosterone as a rapid modulator of cardiovascular responses acting through nongenomic mechanisms.

Efecto de la deshidratación sobre la aldosterona durante una actividad física intensa y de larga duración

Objetivo: Establecer los efectos de la deshidratación sobre la concentración plasmática de aldosterona y sus efectos renales durante una actividad física intensa y de larga duración, en nueve corredores de fondo. Material y métodos: Después de diez minutos de calentamiento, en banda rodante con una pendiente de 1 por ciento y 55 por ciento de la capacidad física de trabajo máxima (PWCmax), siguieron 90 minutos de carrera, al 80 por ciento; fianlente, 90 minutos de recuperación. No se hizo reposición hídrica durante DH (deshidratado); durante RH (rehidratado) se repuso 51 por ciento del peso corporal perdido en DH. Resultados: en DH hubo pérdida de peso corporal y reducción porcentual del volumen plasmático (porcentaje VP). Se observó hiperosmolaridad, hipernatremia, hipercaliemia e hiperaldosteronemia. El índice orina/plasma del sodio disminuyó al final del ejercicio y el del potasio aumentó al final de la recuperación. El índice urinario sodio/potasio disminuyó durante el procedimiento. En RH la pérdida de peso corporal fue menor, pero la reducción porcentaje VP fue similar; con la reposición parcial de las pérdidas hídricas se evitaron la hipersomolaridad y la hipernatremia, pero no la hipercaliemia durante el ejercicio, ni la hiperaldosteronemia durante todo el procedimiento. Los índices orina/plasma para el sodio y el potasio no variaron significativamente. El índice urinario sodio/plasma mostró un comportamiento similar al observado en DH. Conclusiones: La concentración plasmática de aldosterona incrementó proporcionalmente a la duración del ejercicio e independientemente del grado de hidratación; se presentó una respuesta reanl disgregada: inicialmente, un incremento en la reabsorción de sodio y posteriormente, un incremento en la secreción del potasio, en respuesta, posiblemente, a la carga ácida impuesta por acidosis metabólica.

Ultrastructure of the endolymphatic sac in two-phase endolymphatic hydrops in the guinea pig.

Two-phase endolymphatic hydrops is a subtle experimental model for Meniere's disease. Chronic dysfunction of the endolymphatic sac, induced by dissection of the most distal part without causing damage to the intermediate part, is combined with increased endolymph production induced by administration of aldosterone which stimulates the N/K-ATPase in the stria vascularis. A transmission electron microscopic study was performed on the endolymphatic sacs of four groups of guinea pig cochleas: controls: non-operated aldosterone-treated cochleas; operated (dissection of the endolymphatic sac) cochleas; operated and aldosterone-treated cochleas. Light and electron microscopy showed a normal morphology in the controls. Aldosterone treatment had no visible effect. Dissected ears revealed severe deviations. The epithelium of the intermediate sac was low, showed dilated lateral intercellular spaces indicating elevated fluid transport and displayed serious degenerative processes. Distally, the endolymphatic sac was completely blocked by newly formed bone. Additional aldosterone treatment had no cumulative effect on the dissected ears.

Plasticity of hippocampal corticosteroid receptors during aging in the rat.

Aging is commonly associated with dysregulation of the hypothalamo-pituitary-adrenal axis and cognitive impairment. On the basis of suggestions that these disruptions ensue from changes in the hippocampal complement of corticosteroid (mineralocorticoid and glucocorticoid) receptors (MR and GR), we examined the availability of hippocampal MR and GR by measuring the in vivo uptake of 3H-aldosterone and 3H-dexamethasone (selective MR and GR agonists, respectively); MR and GR mRNA levels were also measured. We observed age-related declines in both the synthesis of MR and GR and the uptake of their respective ligands. Whereas MR mRNA levels and ligand uptake declined in parallel, GR binding declined more steeply than GR mRNA. This latter result, together with our finding that aged rats show impaired corticosteroid receptor mRNA and protein up-regulation after corticosteroid withdrawal, indicates decreased transcription of MR and GR genes and posttranslational modification of GR mRNA during aging. Given that corticosteroids can influence MR and GR synthesis and binding, and based on the finding that aged subjects show reduced basal secretion of corticosterone, we propose that this relative hypocorticalism may be responsible for the changes observed in MR and GR activity, which then leads to disturbances in neuroendocrine regulation and cognitive function in aged subjects.

Two-phase endolymphatic hydrops: a new dynamic guinea pig model.

The classical guinea pig model for Meniere's disease, in which endolymphatic hydrops was achieved by destruction of the endolymphatic sac and obliteration of the endolymphatic duct, is a non-physiological profound model with shortcomings in relation to Meniere's disease as seen in patients. We developed a more subtle animal model; the two-phase endolymphatic hydrops. This model is based on a combination of chronic endolymphatic sac dysfunction, induced by slight destruction of the most distal part of the endolymphatic sac, and acute stress-induced endolymph production by stimulation of the Na/K-ATPase in the stria vascularis with aldosterone. Light microscopy of the fluid compartments of four groups of cochleas was used to examine them for the presence of endolymphatic hydrops: i) Normal (control) cochleas showed no hydrops; ii) some of the non-operated (no destruction) aldosterone-treated cochleas showed small degrees of hydrops mainly present in the basal turns; iii) mild dissection of the endolymphatic sac without administration of aldosterone produced a hydrops which was mainly present in the cochlear apex; iv) combination of chronic endolymphatic sac dysfunction and acute attacks of endolymph production by aldosterone administration revealed the most severe degrees of hydrops in all cochlear windings, damage to cochlear structures, and cellular disturbances of the epithelial lining of the endolymphatic sac. This new model may represent a more physiologic and dynamic approach to Meniere's disease and may explain the etiology of many symptoms in patients such as the fluctuant nature and the types of sensoneuronal hearing losses.

Sodium-retaining activity of some natural and synthetic 21-deoxysteroids.

The effect of progesterone and six other C21-deoxysteroids on renal sodium retention by male adrenalectomized rats was compared with the effect exerted by the natural corticoids aldosterone, 11-deoxycorticosterone, and corticosterone. Steroids were active in the following order: aldosterone > 11,19-oxidoprogesterone > 5 alpha H-3,20-pregnanedione > or = 5 beta H-3,20-pregnanedione > progesterone = 11-ketoprogesterone > 6,19-oxidoprogesterone = 11-keto-6,19-oxidoprogesterone > or = corticosterone. All C21-deoxysteroids, except 11,19-oxidoprogesterone, exhibited parabolic log dose-response functions, indicating an effect that opposes renal sodium retention at high doses. 11,19-Oxidoprogesterone and the natural corticoids exhibited normal, exponential, log dose-response curves. Diverse geometric parameters related to molecular planarity were calculated and their correlation with biopharmacological properties was attempted. The best linear regression was obtained for correlation of the concavity of log dose-response parabolas (second-order coefficients) of C21-deoxysteroids with the C3 = O/ring D angle of these molecules. A good linear regression could also be obtained for correlation of the affinity of C21-deoxysteroids, except 11,19-oxidoprogesterone, for purified type I mineralocorticoid receptors with those angles. The latter correlation deteriorated upon incorporation of the affinity data for the three natural corticoids, due to similar affinities of these hormones for type I mineralocorticoid receptors, but could be restored when the binding data for the unpurified, corticosterone-binding globulin-containing stage of the receptors were considered. In vivo binding data followed the same trend as that for unpurified receptors.

Colocalization of 11 beta-hydroxysteroid dehydrogenase and mineralocorticoid receptors in cultured vascular smooth muscle cells.

Colocalization of mineralocorticoid receptors (MR) and 11 beta-hydroxysteroid dehydrogenase (11-HSD), the enzyme acting as a protector of MR, in the same cell of mineralocorticoid (MC)-responsive tissues is crucial to the concept of enzymic regulation of intracellular cortisol levels in these tissues. Such colocalization was demonstrated in the epithelial cells of the renal distal tubule. The aim of the present study was to examine if MR and 11-HSD activity can be colocalized in cells of another target tissue to mineralocorticoids, the arteries. Vascular smooth muscle (VSM) cells were cultured, and absence of dedifferentiation was ascertained up to the eighth passage. High affinity binding of [3H]aldosterone (ALDO) was demonstrated in the intact cultured cells, and Kd and Bmax values were calculated from Scatchard plots. The activity of 11-HSD was demonstrated in the cultured cells by incubating them with [3H]-cortisol in the presence of cofactors, and isolating [3H]-cortisone. Other [3H]-metabolites formed were 11 beta-hydroxy- and 11-keto-androstenedione. These data support the view that arterial tree is a target organ for mineralocorticoids and may be of importance in the pathogenetic mechanism of MC-induced hypertension.