Nongenomic Effect Of Aldosterone Research Articles

The role of central amygdaloid nucleus in regulating the nongenomic effect of aldosterone on sodium intake in the nucleus tractus solitary

ObjectiveThe central nucleus of the amygdala (CeA) has dense downward fiber projections towards the nucleus tractus solitary (NTS) and can modulate the activity of NTS taste neurons. However, whether CeA affects the nongenomic role of aldosterone (ALD) in regulating sodium intake at the NTS level remains unclear.MethodsFirst, 40 adult male Sprague Dawley rats were divided into five groups, referring to different concentrations of ALD, to observe the sodium intake pattern compared with the vehicle (n = 8). ALD, the mineralocorticoid receptor antagonist spironolactone (SPI), and ALD + SPI were injected into the NTS. Then, the rats were divided into four groups (n = 16): bilateral/unilateral CeA electrolytic lesions, bilateral/unilateral CeA sham lesions. After recovery, one stainless steel 23‐gauge cannula with two tubes was implanted into the rat NTS, and all rats underwent a recovery period of 7 days. Then, each group was divided into two subgroups that received aldosterone or control solution injection, and the cumulative intake of 0.3 mol/L NaCl solution was recorded within 30 min.ResultsBilateral CeA lesion eliminated the increased 0.3 mol/L NaCl intake induced by aldosterone microinjected into the NTS (CeA lesion: 0.3 ± 0.04 ml/30 min vs. sham lesion: 1.3 ± 0.3 ml/30 min). Unilateral CeA lesion reduced the increased NaCl intake induced by aldosterone microinjected into the NTS compared with the control group (p < .05) in the first 15 min but not in 15–30 min (p > .05). In sham lesion rats, aldosterone (5 ng/0.1 μl) still induced a significant increase in NaCl intake (aldosterone: 1.3 ± 0.3 ml/30 min vs. control: 0.25 ± 0.02 ml/30 min) (p < .05).ConclusionThe results verified that the complete CeA may play an important role in aldosterone to regulate the nongenomic effect on rapid sodium intake.

The role of free radical oxidation in the kidneys in the nephroprotective action of eplerenone, a mineralocorticoid receptor antagonist, in experimental diabetes mellitus

Aim. To study the effect of eplerenone on the activity of free radical oxidation and renal function in rats with experimental diabetes mellitus induced by streptozotocin. Materials and methods . Experiments were carried out on 36 male Wistar rats. Diabetes mellitus (DM) was simulated by a single intraperitoneal injection of streptozotocin at a dose of 65 mg/kg. Eplerenone was injected into the stomach at a dose of 50 mg/kg. Results. It was found that eplerenone in experimental diabetic nephropathy (DN) significantly attenuated proteinuria: the concentration of protein in the urine became 4 times lower than in untreated DN ( p &lt; 0.001). In the kidneys, eplerenone therapy normalized the structure and function of renal glomeruli and restored the podocyte number, which was reduced by 37.8% in the DN model. Free radical oxidation (FRO) in the kidneys of rats treated with eplerenone increased – the concentration of thiobarbituric acid reactive substances rose by 1.5 times ( p = 0.009), and changes in the activity of antioxidant enzymes, such as superoxide dismutase (a decrease by 2.4 times, p = 0.002), catalase (an increase by 1.8 times, р &lt; 0,001), and glutathione peroxidase (an increase by 1.5 times, р &lt; 0.001) were observed, as opposed to the values in the controls. Conclusion. In streptozotocin-induced experimental diabetic nephropathy in rats, eplerenone had a nephroprotective effect, but increased oxidative stress in the kidneys. The increase in FRO could be determined by the nongenomic effect of aldosterone, which accumulates under conditions of prolonged mineralocorticoid receptor (MR) blockade. The nephroprotective effect of eplerenone can be associated with the weakening of the genomic effects of aldosterone, realized with the participation of MR.

Видовые особенности негеномной реакции главных клеток собирательных трубок почек крыс и мышей на альдостерон

We have previously shown the fast nongenomic effect of aldosterone on intracellular sodium ([Na+]i) in the principal cells of rat kidney cortical collecting duct (CCD) in low sodium outer medium (14 mM NaCl). The method of fluorescence microscopy with the intracellular dye Sodium Green was used to study the rate of [Na+]i changes in response to external sodium shift (from 137 to 14 mM ) in Wistar rat and C57bl/6 mouse principal cells. In the presence of aldosterone (10 nM), the level of intracellular sodium in the rat principal cells was higher than in control at the low sodium medium (14 mM NaCl) (р˂0.05). In the principal cells of the mice kidney CCD, the response to a sharp change in the sodium level in the outer medium was significantly faster than we have found in rat, and the nongenomic response to aldosterone (10 nM) was weaker than in rats (р˂0.05). The data obtained for the first time demonstrated the differences in the fast nongenomic aldosterone effects in the principal cells of rat and mice CCD on intracellular sodium balance.

Role of the central nucleus of the amygdala in regulating the nongenomic effect of aldosterone on sodium intake in rat nucleus tractus solitarius

To reveal the nongenomic effect of aldosterone on the regulation of sodium intake in the nucleus tractus solitarius (NTS) and the role of central nucleus of the amygdala (CeA) in regulating this effect. Adult male SD rats were divided into four groups and underwent operations to induce bilateral CeA electrolytic lesions (400 μA, 25 s; n=28), bilateral sham CeA lesions (n=28), unilateral CeA lesions (n=28), or unilateral sham CeA lesions (n=26). After 3 days of recovery, the rats received implantation of a stainless steel 23-gauge cannula wih two tubes into the NTS followed by a recovery period of 7 days. The rats in each group were then divided into two subgroups for microinjection of aldosterone (50 ng/μL) or control solution in the NTS, and the cumulative intake within 30 min of 0.3 mol/L NaCl solution was recorded for each rat. Bilateral CeA lesions (3 days) eliminated the increased 0.3 mol/L NaCl intake induced by aldosterone microinjected into the NTS (0.3±0.04 mL in CeA lesion group vs 1.3±0.3 mL in sham lesion group). Unilateral CeA lesion (3 days) reduced aldosterone-induced increase of NaCl intake in the first 15 min (P &lt; 0.05) but not in 15-30 min (P &gt; 0.05). In rats with sham lesions, aldosterone (50 ng/μL) still induced a significant increase in NaCl intake[1.3±0.3 mL vs 0.25±0.02 mL in the control group; F (3, 224)=24.0, P &lt; 0.05]. The regulation of sodium intake by aldosterone is subjected to descending facilitatory modulation by the bilateral CeA, and CeA integrity is essential for aldosterone to execute the nongenomic effect in regulating rapid sodium intake.

Nongenomic effect of aldosterone on angiotensin II type 1 receptor dimerization in human renal proximal tubular cells: Implications for endoplasmic reticulum stress

Nongenomic effect of aldosterone on angiotensin II type 1 receptor dimerization in human renal proximal tubular cells: Implications for endoplasmic reticulum stress

Fast Nongenomic Effect of Aldosterone on the Volume of Principal Cells in Collecting Tube and Genetic Heterogeneity of Epithelial Sodium Channel in the Postnatal Ontogenesis of Rat Kidney.

The effects of amiloride, epithelial sodium pump inhibitor, on the fast nongenomic effect of aldosterone in principal cells of an isolated segment of the distal portion of renal collecting tubes were studied in 10-day-old and adult rats. Fluorescent staining with Calcein AM showed various effects of amiloride (10(-5) M) on the stabilizing effect of aldosterone (10 nM) in hypotonic shock (280/140 mOsm/kg). Amiloride attenuated by 30% the effect of aldosterone on the amplitude of principal cell swelling in adult animals and almost completely abolished this effect in 10-day rats (p<0.05). These age-specific differences in the contribution of the distal portion of the collecting tube to the nongenomic effect of aldosterone did not depend on genetic heterogeneity of its α-subunit.

Action of ANP on the nongenomic dose-dependent biphasic effect of aldosterone on NHE1 in proximal S3 segment

The rapid (2min) nongenomic effects of aldosterone (ALDO) and/or spironolactone (MR antagonist), RU 486 (GR antagonist), atrial natriuretic peptide (ANP) and dimethyl-BAPTA (BAPTA) on the intracellular pH recovery rate (pHirr) via NHE1 (basolateral Na+/H+ exchanger isoform), after the acid load induced by NH4Cl, and on the cytosolic free calcium concentration ([Ca2+]i) were investigated in the proximal S3 segment isolated from rats, by the probes BCECF-AM and FLUO-4-AM, respectively. The basal pHi was 7.15±0.008 and the basal pHirr was 0.195±0.012pHunits/min (number of tubules/number of tubular areas=16/96). Our results confirmed the rapid biphasic effect of ALDO on NHE1: ALDO (10−12M) increases the pHirr to approximately 59% of control value, and ALDO (10−6M) decreases it to approximately 49%. Spironolactone did not change these effects, but RU 486 inhibited the stimulatory effect and maintained the inhibitory effect. ANP (10−6M) or BAPTA (5×10−5M) alone had no significant effect on NHE1 but prevented both effects of ALDO on this exchanger. The basal [Ca2+]i was 104±3nM (15), and ALDO (10−12 or 10−6M) increased the basal [Ca2+]i to approximately 50% or 124%, respectively. RU 486, ANP and BAPTA decreased the [Ca2+]i and inhibited the stimulatory effect of both doses of ALDO. The results suggest the involvement of GR on the nongenomic effects of ALDO and indicate a pHirr-regulating role for [Ca2+]i that is mediated by NHE1, stimulated/impaired by ALDO, and affected by ANP or BAPTA with ALDO. The observed nongenomic hormonal interaction in the S3 segment may represent a rapid and physiologically relevant regulatory mechanism in the intact animal under conditions of volume alterations.

Activation of Src-ATF1 pathway is involved in upregulation of Nox1, a catalytic subunit of NADPH oxidase, by aldosterone

In this study, we mainly focused on how aldosterone regulates Nox1, a catalytic subunit of NADPH oxidase (NOX) in vascular smooth muscle cells (VSMC). We found that aldosterone can induce the expression of Nox1, which is upregulated by the activation of the Src and activating transcription factor 1 (ATF1), but can not be suppressed by the inhibitors of the epidermal growth factor receptor (EGFR) or Matrix Metalloproteinase (MMP). Aldosterone triggers ATF1 phosphorylation in dose dependent fashion, but this effect is not blocked by actinomycin D, suggesting a non-genomic effect of aldosterone. On the other hand, aldosterone induced Nox1 expression can be suppressed by the gene silencing of the ATF1 using RNA interference. Furthermore, silencing ATF1 can also attenuate aldosterone-induced O(2)(-) production and protein synthesis, and inhibit hypertrophy in this vascular cell lineage. In short, our results primarily unveiled the relationship between aldosterone and Nox1 expression and the regulation mechanism of their signal pathways in the hypertrophy of vascular smooth muscle cell. Src, ATF1, Nox1 and MR are likely efficient targets in the treating of vascular diseases but need more study.

Genomic and nongenomic stimulatory effect of aldosterone on H+-ATPase in proximal S3 segments

The genomic and nongenomic effects of aldosterone on the intracellular pH recovery rate (pHirr) via H(+)-ATPase and on cytosolic free calcium concentration ([Ca(2+)](i)) were investigated in isolated proximal S3 segments of rats during superfusion with an Na(+)-free solution, by using the fluorescent probes BCECF-AM and FLUO-4-AM, respectively. The pHirr, after cellular acidification with a NH(4)Cl pulse, was 0.064 ± 0.003 pH units/min (n = 17/74) and was abolished with concanamycin. Aldosterone (10(-12), 10(-10), 10(-8), or 10(-6) M with 1-h or 15- or 2-min preincubation) increased the pHirr. The baseline [Ca(2+)](i) was 103 ± 2 nM (n = 58). After 1 min of aldosterone preincubation, there was a transient and dose-dependent increase in [Ca(2+)](i) and after 6-min preincubation there was a new increase in [Ca(2+)](i) that persisted after 1 h. Spironolactone [mineralocorticoid (MR) antagonist], actinomycin D, or cycloheximide did not affect the effects of aldosterone (15- or 2-min preincubation) on pHirr and on [Ca(2+)](i) but inhibited the effects of aldosterone (1-h preincubation) on these parameters. RU 486 [glucocorticoid (GR) antagonist] and dimethyl-BAPTA (Ca(2+) chelator) prevented the effect of aldosterone on both parameters. The data indicate a genomic (1 h, via MR) and a nongenomic action (15 or 2 min, probably via GR) on the H(+)-ATPase and on [Ca(2+)](i). The results are compatible with stimulation of the H(+)-ATPase by increases in [Ca(2+)](i) (at 10(-12)-10(-6) M aldosterone) and inhibition of the H(+)-ATPase by decreases in [Ca(2+)](i) (at 10(-12) or 10(-6) M aldosterone plus RU 486).

Epithelial Na+ Channel (ENaC), Hormones, and Hypertension

This minireview examines both the basic science and clinical observations over the past 20 years to show how and why overstimulation of the amiloride-sensitive epithelial Na(+) channel (ENaC) expressed by epithelial principal cells of the renal collecting duct may be responsible for a large portion of hypertension in modern society. This idea is based on the finding that, in Liddle syndrome, a mutation of the beta- and/or gamma-subunits of ENaC produces an activated ion channel, in turn resulting in severe hypertension that is resistant to most forms of conventional antihypertensive therapy. ENaC can also be stimulated to conduct sodium by two hormones: aldosterone and insulin. These hormones are both often elevated in obese individuals with therapy-resistant hypertension. Thus, overstimulation of ENaC by metabolic abnormalities in obese individuals may be a likely cause of the hypertension that accompanies obesity. The molecular mechanisms underlying both Liddle syndrome and obesity-related hypertension are different (i.e. genetic and hormonal, respectively), but both have the same end result, namely increased ENaC activity.

Aldosterone activates endothelial exocytosis

Although elevated levels of aldosterone are associated with vascular inflammation, the proinflammatory pathways of aldosterone are not completely defined. We now show that aldosterone triggers endothelial cell exocytosis, the first step in leukocyte trafficking. Exogenous aldosterone stimulates endothelial exocytosis of Weibel-Palade bodies, externalizing P-selectin and releasing von Willebrand factor. Spironolactone, a nonselective mineralocorticoid receptor (MR) blocker, antagonizes aldosterone-induced endothelial exocytosis. Knockdown of the MR also decreases exocytosis, suggesting that the MR mediates exocytosis. Aldosterone triggers exocytosis within minutes, and this effect is not inhibited by actinomycin D, suggesting a nongenomic effect of aldosterone. Aldosterone treatment of endothelial cells increases leukocyte adherence to endothelial cells in culture. Taken together, our data suggest that aldosterone activates vascular inflammation in part through nongenomic, MR-mediated pathways. Aldosterone antagonism may decrease vascular inflammation and cardiac fibrosis in part by blocking endothelial exocytosis.

Effect of aldosterone on the regulation of the volume of principal cells of rat cortical collecting duct epithelium in early postnatal development

A rapid nongenomic regulatory effect of aldosterone on the volume of principal cells in the cortical segment of cortical collecting ducts (CCDs) of rat kidney was studied using the fluorescent dye calcein under hypoosmotic shock conditions (280‐140 mOsm/kg). In the presence of aldosterone (10 nM), the amplitude of cell volume growth significantly decreased ( p < 0.05) and the cell volume recovery time increased twice both in adult and ten-day-old animals. Age differences were detected when the time required for the cell volume recovery under hypoosmotic conditions was determined: in the adult animals, the cell volume recovered much more rapidly (by an order of magnitude) than in the ten-day-old animals both in the control and in the presence of aldosterone ( 0.09 ± 0.02 vs 2.8 ± 0.3 and 0.21 ± 0.03 vs 4.4 ± 0.5 , respectively, p < 0.001). This was the first study to demonstrate the involvement of aldosterone in the regulation of amplitude and dynamics of changes in the volume of CCD principal cells in early postnatal ontogeny. One of the key aspects of development of the osmoregulatory function of the kidney is the development of the molecular mechanisms of regulation of sodium transport in nephron epithelial cells by aldosterone. It is known that, in early ontogeny, kidneys of altricial animals including rats are insensitive to the antinatriuretic effect of aldosterone. Regulation of sodium transport in postnatal ontogeny of the rat is detected starting from the tenth day of life, when the transition from milk feeding to independent feeding is ended. The molecular mechanisms underlying the development of hormonal sensitivity of target cells of an immature kidney have been studied insufficiently well. It is known that the main proteins involved in the transmembrane sodium transport in the principal cells of the CCDs of rat nephron are the proteins of the apical epithelial of the sodium channel (ENaC) and the basolateral sodium pump ( Na + ,a + -ATPase) [6, 7]. The intracellular sodium concentration ([ ]) in principal cells is primarily determined by the dynamic equilibrium between the sodium influx through ENaC and its efflux form the cell into the intersticium against the concentration gradient by ATP-driven Na + ,a + -ATPase. Earlier, we showed that the expression of the genes encoding these proteins is suppressed and the intracellular sodium concentration in CCD principal cells is decreased in kidneys of tenday-old animals [1, 4]. At the same time, we discovered that aldosterone had a rapid nongenomic effect expressed in maintaining an increased [ ] in CCD principal cells at a low (14 mM) sodium concentration in the ambient medium both in adult and ten-day-old rats [4]. These data led us to assume that, along with the well-known mineralocorticoid effect, aldosterone is also involved in the regulation of the volume of CCD cells in rat nephron in hypoosmotic medium and that this mechanism functions even in the preweaning period. However, the rapid nongenomic effects of aldosterone on the regulation of the volume of CCD principal cells have been studied insufficiently comprehensively. In view of above, the goal of this study was to investigate the rapid nongenomic effect of aldosterone at a physiological concentration on the volume of CCD principal cells in kidneys of ten-day-old and adult rats under hypoosmotic shock conditions. Experiments were performed with CCDs of ten- and sixty-day-old Wistar rats, which were obtained by microdissection. The changes in the cell volume were assessed by the changes in the fluorescence intensity of the intracellular dye calcein and expressed in relative units. Fluorescence intensity was measured in the cells located at the open end of a CCD fragment; the basolateral and apical surfaces of these cells are in contact with the ambient solution. Continuous fluorescence recording during cell volume changes in response to osmotic shock was performed in our modification [11]. Renal tubule fragments contained in 100 µ l of suspension in aOa culture medium were loaded on a polylysinecoated slide and loaded with the fluorescent dye calcein

Effect of aldosterone on kinetics of intracellular sodium in cortical portion of collecting ducts in rat kidney

We studied the effect of protein kinase C inhibitor RO-31-8220 (10(-7) M) on rapid nongenomic effect of aldosterone in cells of isolated segment of distal region of collecting duct in rat kidney. Experiments with fluorescent dye Na-Green showed that the inhibitor abolished the modulating effect of aldosterone (10 nM) on intracellular sodium concentration at external sodium concentration of 14 mM. Aldosterone decreased by half the initial rate of the changes in internal sodium concentration in both 10-day and mature rats (p<0.05). Similarly to sodium channel blocker amiloride (10(-5) M), RO-31-8220 abolished rapid nongenomic effect of aldosterone on the rate of the changes in internal sodium concentration.

Nongenomic Effect of Aldosterone on Ion Transport Pathways of Red Blood Cells

The direct influence of aldosterone on the human and avian red blood cell (RBC) transport systems, Na⁺/K⁺ pump, Na⁺,K⁺,2Cl^- symporter, and K⁺ (Na⁺)/H⁺ exchanger, was investigated with tracer kinetics. The present work proved that aldosterone has no significant effect on these transport pathways. However, in young human RBCs containing reticulocytes aldosterone showed a significant inhibition of the Na⁺,K⁺,2Cl^- symporter. Investigations of the Li⁺ efflux via the Na⁺/Li⁺ exchanger using atom absorption spectroscopy revealed that aldosterone has no effect on this transporter. Studies of the effect of aldosterone on the Ca²⁺ content and the intracellular pH (pH_i) were carried out on single RBCs with a fluorescence imaging system. Both parameters are affected by aldosterone. The Ca²⁺ uptake in the presence of aldosterone, under conditions where the Ca²⁺ pump is inhibited, showed marked differences from the control. Since the effect is nifedipine-sensitive, it seems that aldosterone affects a Ca²⁺ channel. In addition, aldosterone leads to an acidification of the intracellular medium after an initial alkalisation due to an effect on the Na⁺/H⁺ exchanger.

Nongenomic Renal Effects of Aldosterone

There is increasing evidence for a dependency on aldosterone in the development of hypertension.1 How aldosterone influences the physiology that determines blood pressure or for that matter promotes the pathophysiology of high blood pressure turns out to be less than straightforward. There is the genomic pathway that begins with the binding of aldosterone to the classical mineralocorticoid receptor (MR) and ends with sodium reabsorption at the distal nephron. But aldosterone can convey nongenomic influences as well, actions that have received less attention, possibly in part because they seem counterintuitive to our genomic view of biology. Adding to the complexity of aldosterone’s actions is the fact that there are also nonepithelial (nondistal nephron) targets of aldosterone, such as the heart, the vasculature, the kidney, and other sites. In this issue of Hypertension , Schmidt et al2 describe a rapid (thus nongenomic) effect of administered aldosterone to increase resistance in renal vasculature (a nonepithelial target) in healthy human subjects. The findings follow on the heels of a rather large body of work on the genomic actions of aldosterone. Aldosterone’s nongenomic effects were first recognized more than a decade before an aldosterone-inducible gene was identified in the late 1990s.3 A nongenomic action characteristically occurs almost immediately, usually within several minutes,4 before sufficient time has elapsed for gene …

A rapid nongenomic effect of aldosterone on intracellular sodium concentration in the distal nephron segment of the rat

A rapid nongenomic effect of aldosterone on intracellular sodium concentration in the distal nephron segment of the rat

Aldosterone Rapidly Activates Na+/H+ Exchange in M-1 Cortical Collecting Duct Cells via a PKC-MAPK Pathway

Background: In this study, the mechanism of the rapid non-genomic effect of aldosterone on Na⁺/H⁺ exchanger (NHE)-mediated intracellular pH (pH_i) recovery from an acid load in murine M-1 cortical collecting duct cells was assessed. Methods: Spectrofluorescence microscopy and Western blot analysis was carried out and NH₄Cl was used to induce the acid load. Results: Aldosterone (10 nM) induced a rapid (<5 min) concentration-dependent increase in pH_i recovery in M-1 cells, an effect mimicked by its precursor deoxycorticosterone (1 nM). This response was unaffected by the mineralocorticoid receptor (MR) antagonist spironolactone (10 µM) but was significantly reduced by the NHE antagonists 5′-(N-ethyl- N-isopropyl)amiloride (EIPA) (20 µM) and cariporide (1 µM). The PKC inhibitor chelerythrine chloride (1 µM) significantly attenuated the aldosterone-induced increase in NHE1 activity. HBDDE (80 µM), a PKC_α inhibitor, inhibited the rapid aldosterone effect whereas rottlerin (15 µM), a PKC_δ antagonist, did not. The glucocorticoid receptor agonists hydrocortisone (1 µM) and dexamethasone (100 nM) decreased NHE activity, whereas the synthetic mineralocorticoid fludrocortisone (1 nM) had no significant effect. MAPK inhibition using PD98059 (25 µM) significantly attenuated the rapid aldosterone effect; Western blot analysis showed that aldosterone activation of ERK 1/2 was unaffected by pretreatment with spironolactone but was inhibited following chelerythrine chloride. Conclusion: Aldosterone causes a rapid non-genomic increase in NHE1 activity in M-1 cells via a PKC_α/MAPK pathway independent of the classical MR.

Non-genomic effects of aldosterone: new actions and questions

Although the classical actions of aldosterone are mediated through genomic pathways, there is a growing recognition of important nongenomic responses to aldosterone. New data are presented from two laboratories showing a nongenomic effect of aldosterone to activate protein kinase C (PKC) in heart and kidney. Among the actions of PKC is the stimulation of transcription factors, raising the question of whether there is an inter-relationship of nongenomic with genomic influences--aldosterone induced nongenomic effects might modulate genomic effects. This expanded role of aldosterone will require exploration in future studies.

Nongenomic effect of aldosterone on Na+,K+-adenosine triphosphatase in arterial vessels.

Aldosterone increases Na(+),K(+)-adenosine triphophatase (Na(+),K(+)-ATPase) pump activity and abundance under chronic conditions in several tissues, including rat arterial vessels. The present study was undertaken to evaluate whether aldosterone has also short-term effects on the Na(+),K(+)-ATPase of rat aorta. The pump function was measured as ouabain-sensitive (86)Rb/K uptake in aortic rings. Addition of aldosterone induced a rapid inhibition of the Na(+),K(+)-ATPase (57.0 +/- 2.3% of control values; P < 0.05; n = 8), followed by a return to control values after 120 min. The aldosterone-induced decrease in ouabain-sensitive (86)Rb/K uptake was prevented by the new mineralocorticoid receptor antagonist eplerenone. The inhibition of gene transcription (actinomycin D) or protein synthesis (cycloheximide) had no effect on short-term aldosterone action on Na(+),K(+)-ATPase. The rapid aldosterone inhibition was also observed in the presence of monensin, a sodium-specific ionophore. Rapamycin, an immunosuppressive drug that stabilizes the heat shock protein-steroid receptor complex, blocked the rapid aldosterone effect. Bisindole I, an inhibitor of protein kinase C, also blocked nongenomic action of aldosterone on the Na pump. The nongenomic effect of aldosterone was inhibited by disrupters of microtubule (colchicine). Plasma membrane protein biotinylation of aortic segments and Western blot indicated a diminished presence of catalytic isoforms of Na(+),K(+)-ATPase on the cell surface. Our findings indicate that aldosterone has a nongenomic effect on the Na(+),K(+)-ATPase of vascular tissue. This effect is mediated through protein kinase C activation and implies reduced cell surface abundance of catalytic subunits. These observations together with our previous report on chronic hormone replacement suggest that aldosterone is directly involved in ionic cellular homeostasis of the vascular system through Na pump regulation.

Aldosterone induces contraction of the resistance arteries in man

Very rapid nongenomic effects of aldosterone in vitro have been described in recent years and in vivo evidence has been reported as well. In the present study, we investigated the rapid effect of aldosterone on resistance arteries in vivo in man. We performed a randomized, placebo-controlled, double-blind crossover study on ten healthy male volunteers. Forearm blood flow (FBF) was measured using venous occlusion plethysmography in both forearms. FBF was reduced by administration of aldosterone 2.5 pmol/min at min 4 (from 4.45±0.03 to 3.3±0.25 ml/100 ml tissue) and reached its nadir at min 12 (from 4.45±0.03 to 1.6±0.08 ml/100 ml tissue, P<0.001). Our study documents a direct nongenomic effect of aldosterone on the resistance arteries in vivo in man. The rapid vasoconstrictive effect of aldosterone at physiological concentrations opens the way to investigations on the vascular role of this steroid in several disorders, such as hypertension, characterized by elevated peripheral vascular resistance.