RESUMEN
A thin fluid layer in alveoli is normal and results from a balance of fluid entry and fluid uptake by transepithelial salt and water reabsorption. Conventional wisdom suggests the reabsorption is via epithelial Na+ channels (ENaC), but if all Na+ reabsorption were via ENaC, then amiloride, an ENaC inhibitor, should block alveolar fluid clearance (AFC). However, amiloride blocks only half of AFC. The reason for failure to block is clear from single-channel measurements from alveolar epithelial cells: ENaC channels are observed, but another channel is present at the same frequency that is nonselective for Na+ over K+, has a larger conductance, and has shorter open and closed times. These two channel types are known as highly selective channels (HSC) and nonselective cation channels (NSC). HSC channels are made up of three ENaC subunits since knocking down any of the subunits reduces HSC number. NSC channels contain α-ENaC since knocking down α-ENaC reduces the number of NSC (knocking down ß- or γ-ENaC has no effect on NSC, but the molecular composition of NSC channels remains unclear). We show that NSC channels consist of at least one α-ENaC and one or more acid-sensing ion channel 1a (ASIC1a) proteins. Knocking down either α-ENaC or ASIC1a reduces both NSC and HSC number, and no NSC channels are observable in single-channel patches on lung slices from ASIC1a knockout mice. AFC is reduced in knockout mice, and wet wt-to-dry wt ratio is increased, but the percentage increase in wet wt-to-dry wt ratio is larger than expected based on the reduction in AFC.
Asunto(s)
Canales Iónicos Sensibles al Ácido/metabolismo , Canales Epiteliales de Sodio/metabolismo , Alveolos Pulmonares/metabolismo , Células Epiteliales Alveolares/efectos de los fármacos , Células Epiteliales Alveolares/metabolismo , Animales , Líquido del Lavado Bronquioalveolar , Células Cultivadas , Activación del Canal Iónico/efectos de los fármacos , Ratones Endogámicos C57BL , Ratones Noqueados , Modelos Biológicos , Oxígeno/farmacología , Unión Proteica/efectos de los fármacos , Subunidades de Proteína/metabolismo , Alveolos Pulmonares/efectos de los fármacos , Venenos de Serpiente/toxicidad , Agua/metabolismoRESUMEN
Many hormonal pathways contribute to the regulation of renal epithelial sodium channel (ENaC) function, a key process for maintaining blood volume and controlling blood pressure. In the present study, we examined whether the peptide hormone prolactin (PRL) regulates ENaC function in renal epithelial cells (A6). Basolateral application of several different concentrations of PRL dramatically stimulated the transepithelial current in A6 cells, increasing both amiloride-sensitive (ENaC) and amiloride-insensitive currents. Using cell-attached patch clamp, we determined that PRL increased both the number (N) and open probability (Po) of ENaC present in the apical membrane. Inhibition of PKA with H-89 abolished the effect of PRL on amiloride-sensitive and insensitive transepithelial currents and eliminated the increase in ENaC NPo with PRL exposure. PRL also increased cAMP in A6 cells, consistent with signaling through the cAMP-dependent PKA pathway. We also identified that PRL induced activity of a 2-pS anion channel with outward rectification, electrophysiological properties consistent with ClC4 or ClC5. RT-PCR only detected ClC4, but not ClC5 transcripts. Here, we show for the first time that PRL activates sodium and chloride transport in renal epithelial cells via ENaC and ClC4.
Asunto(s)
Canales de Cloruro/metabolismo , Células Epiteliales/efectos de los fármacos , Canales Epiteliales de Sodio/metabolismo , Prolactina/farmacología , Sodio/metabolismo , Amilorida/farmacología , Animales , Línea Celular , AMP Cíclico/metabolismo , Células Epiteliales/metabolismo , Ratones , Técnicas de Placa-Clamp/métodosRESUMEN
Female sex predisposes individuals to poorer outcomes during respiratory disorders like cystic fibrosis and influenza-associated pneumonia. A common link between these disorders is dysregulation of alveolar fluid clearance via disruption of epithelial sodium channel (ENaC) activity. Recent evidence suggests that female sex hormones directly regulate expression and activity of alveolar ENaC. In our study, we identified the mechanism by which estradiol (E2) or progesterone (P4) independently regulates alveolar ENaC. Using cell-attached patch clamp, we measured ENaC single-channel activity in a rat alveolar cell line (L2) in response to overnight exposure to either E2 or P4. In contrast to P4, E2 increased ENaC channel activity (NPo) through an increase in channel open probability (Po) and an increased number of patches with observable channel activity. Apical plasma membrane abundance of the ENaC α-subunit (αENaC) more than doubled in response to E2 as determined by cell surface biotinylation. αENaC membrane abundance was approximately threefold greater in lungs from female rats in proestrus, when serum E2 is greatest, compared with diestrus, when it is lowest. Our results also revealed a significant role for the G protein-coupled estrogen receptor (Gper) to mediate E2's effects on ENaC. Overall, our results demonstrate that E2 signaling through Gper selectively activates alveolar ENaC through an effect on channel gating and channel density, the latter via greater trafficking of channels to the plasma membrane. The results presented herein implicate E2-mediated regulation of alveolar sodium channels in the sex differences observed in the pathogenesis of several pulmonary diseases.
Asunto(s)
Células Epiteliales Alveolares/metabolismo , Canales Epiteliales de Sodio/metabolismo , Estradiol/fisiología , Receptores de Estrógenos/metabolismo , Receptores Acoplados a Proteínas G/metabolismo , Animales , Células Cultivadas , Canales Epiteliales de Sodio/genética , Congéneres del Estradiol/farmacología , Femenino , Activación del Canal Iónico , Potenciales de la Membrana , Nitrilos/farmacología , Proestro/metabolismo , Transporte de Proteínas , Ratas , Ratas WistarRESUMEN
A consistent clinical finding in patients with major depressive disorder (MDD) is hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis, the system in the body that facilitates the response to stress. It has been suggested that alterations in glucocorticoid receptor (GR)-mediated feedback prolong activation of the HPA axis, leading to the dysfunction observed in MDD. Additionally, the risk for developing MDD is heightened by several risk factors, namely gender, genetics and early life stress. Previous studies have demonstrated that GR translocation is sexually dimorphic and this difference may be facilitated by differential expression of GR co-regulators. The purpose of this study was to determine the extent to which ovarian hormones alter expression of GR and its co-regulators, Fkbp5 and Ppid, in HT-22 hippocampal neurons. The impact of corticosterone (cort), estradiol (E2), and progesterone (P4) treatments on the expression of the genes Nr3c1, Ppid, and Fkbp5 was assessed in HT-22 hippocampal neurons. Treatment of cells with increasing doses of cort increased the expression of Fkbp5, an effect that was potentiated by E2. Exposure of HT-22 cells to E2 decreased the expression of Ppid and simultaneous exposure to E2 and P4 had combinatory effects on Ppid expression. The effects of E2 on Ppid extend previous work which demonstrated that serum E2 concentrations correlate with hippocampal Ppid expression in female rats. The results presented here illustrate that E2 generates an anti-translocation pattern of GR co-regulators in hippocampal cells.
Asunto(s)
Ciclofilinas/metabolismo , Estradiol/farmacología , Hipocampo/efectos de los fármacos , Neuronas/efectos de los fármacos , Receptores de Glucocorticoides/metabolismo , Proteínas de Unión a Tacrolimus/metabolismo , Animales , Línea Celular , Corticosterona/farmacología , Ciclofilinas/genética , Hipocampo/metabolismo , Neuronas/metabolismo , Progesterona/farmacología , Ratas , Receptores de Glucocorticoides/genética , Proteínas de Unión a Tacrolimus/genéticaRESUMEN
Increasing evidence suggests that the circadian clock plays an important role in the control of renal function and blood pressure. We previously showed that the circadian clock protein Period (Per)1, positively regulates the expression of the rate limiting subunit of the renal epithelial sodium channel (αENaC), which contributes to blood pressure regulation. Casein kinases 1δ and 1ε (CK1δ/ε) are critical regulators of clock proteins. CK1δ/ε must phosphorylate the circadian clock protein Per1 in order for the latter to enter the nucleus. We used a commercially available CK1δ/ε inhibitor, PF670462, to test the effect of CK1δ/ε blockade and inhibited Per1 nuclear entry on αENaC in a model of the renal cortical collecting duct (mpkCCD(c14) cells). CK1δ/ε blockade prevented Per1 and Clock from interacting with an E-box from the αENaC promoter. CK1δ/ε inhibition reduced αENaC mRNA levels by <60%. A similar decrease in αENaC mRNA was observed following siRNA-mediated CK1δ/ε knock-down. Inhibition of CK1δ/ε effectively prevented the transcriptional response of αENaC to aldosterone, suggesting an interaction between the circadian clock and aldosterone-mediated regulation of αENaC. CK1δ/ε inhibition significantly reduced αENaC but increased Caveolin-1 membrane protein levels; transepithelial current, a measure of ENaC activity, was decreased. Importantly, single channel analysis in amphibian renal cells demonstrated a dramatic decrease in the number of patches with observable ENaC current following CK1δ/ε inhibition. The present study shows for the first time that CK1δ/ε inhibition and impaired Per1 nuclear entry results in decreased αENaC expression and ENaC activity, providing further support for direct control of ENaC by the circadian clock.
Asunto(s)
Caseína Cinasa 1 épsilon/antagonistas & inhibidores , Quinasa Idelta de la Caseína/antagonistas & inhibidores , Canales Epiteliales de Sodio/metabolismo , Túbulos Renales Colectores/metabolismo , Animales , Proteínas CLOCK/metabolismo , Caseína Cinasa 1 épsilon/metabolismo , Quinasa Idelta de la Caseína/metabolismo , Línea Celular , Células Cultivadas , Canales Epiteliales de Sodio/genética , Túbulos Renales Colectores/efectos de los fármacos , Ratones , Proteínas Circadianas Period/metabolismo , Fosforilación , Pirimidinas/farmacologíaRESUMEN
The circadian clock protein period 1 (Per1) contributes to the regulation of expression of the α subunit of the renal epithelial sodium channel at the basal level and in response to the mineralocorticoid hormone aldosterone. The goals of the present study were to define the role of Per1 in the regulation of additional renal sodium handling genes in cortical collecting duct cells and to evaluate blood pressure (BP) in mice lacking functional Per1. To determine whether Per1 regulates additional genes important in renal sodium handling, a candidate gene approach was used. Immortalized collecting duct cells were transfected with a nontarget small interfering RNA or a Per1-specific small interfering RNA. Expression of the genes for α-epithelial sodium channel and Fxyd5, a positive regulator of Na, K-ATPase activity, decreased in response to Per1 knockdown. Conversely, mRNA expression of caveolin 1, Ube2e3, and ET-1, all negative effectors of epithelial sodium channel, was induced after Per1 knockdown. These results led us to evaluate BP in Per1 KO mice. Mice lacking Per1 exhibit significantly reduced BP and elevated renal ET-1 levels compared with wild-type animals. Given the established role of renal ET-1 in epithelial sodium channel inhibition and BP control, elevated renal ET-1 is one possible explanation for the lower BP observed in Per1 KO mice. These data support a role for the circadian clock protein Per1 in the coordinate regulation of genes involved in renal sodium reabsorption. Importantly, the lower BP observed in Per1 KO mice compared with wild-type mice suggests a role for Per1 in BP control as well.
Asunto(s)
Presión Sanguínea/fisiología , Túbulos Renales Colectores/metabolismo , Proteínas Circadianas Period/metabolismo , Sodio/metabolismo , Animales , Presión Sanguínea/genética , Western Blotting , Caveolina 1/genética , Caveolina 1/metabolismo , Línea Celular , Línea Celular Transformada , Endotelina-1/genética , Endotelina-1/metabolismo , Canales Epiteliales de Sodio/genética , Canales Epiteliales de Sodio/metabolismo , Regulación de la Expresión Génica , Transporte Iónico/genética , Masculino , Ratones , Ratones de la Cepa 129 , Ratones Noqueados , Modelos Genéticos , Proteínas Circadianas Period/genética , Interferencia de ARN , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Enzimas Ubiquitina-Conjugadoras/genética , Enzimas Ubiquitina-Conjugadoras/metabolismoRESUMEN
The adrenal cortex synthesizes many steroids, but the mineralocorticoid aldosterone and the glucocorticoids cortisol and corticosteroid have been viewed as the principal steroids responsible for regulation of renal electrolyte excretion. A study by Elabida et al. challenges that paradigm and suggests that progesterone, classically viewed as a sex steroid, also participates in renal electrolyte balance.
Asunto(s)
Glándulas Suprarrenales/metabolismo , Hipopotasemia/metabolismo , Riñón/metabolismo , Potasio en la Dieta/metabolismo , Progesterona/biosíntesis , Animales , Femenino , Humanos , MasculinoRESUMEN
In the renal collecting duct, mineralocorticoids drive Na(+) reabsorption, K(+) secretion, and H(+) secretion through coordinated actions on apical and basolateral transporters. Whether mineralocorticoids act through H(+),K(+)-ATPases to maintain K(+) and acid-base homeostasis is unknown. Here, treatment of mice with the mineralocorticoid desoxycorticosterone pivalate (DOCP) resulted in weight gain, a decrease in blood [K(+)] and [Cl(-)], and an increase in blood [Na(+)] and [HCO(3)(-)]. DOCP treatment increased the rate of H(+),K(+)-ATPase-mediated H(+) secretion in intercalated cells of the inner cortical collecting duct. mRNA expression of the catalytic subunit HKα(1) did not significantly change, whereas HKα(2) mRNA expression dramatically increased in the outer and inner medulla of DOCP-treated mice. A high-K(+) diet abrogated this increase in renal HKα(2) expression, showing that DOCP-mediated stimulation of HKα(2) expression depends on dietary K(+) intake. DOCP treatment of mice lacking HKα(1) (HKα(1)(-/-)) resulted in greater urinary Na(+) retention than observed in either wild-type mice or mice lacking both HKα(1) and HKα(2) (HKα(1,2)(-/-)). DOCP-treated HKα(1,2)(-/-) mice exhibited a lower blood [HCO(3)(-)] and less Na(+) and K(+) retention than either wild-type or HKα(1)(-/-) mice. Taken together, these results indicate that H(+),K(+)-ATPases-especially the HKα(2)-containing H(+),K(+)-ATPases-play an important role in the effects of mineralocorticoids on K(+), acid-base, and Na(+) balance.
Asunto(s)
Equilibrio Ácido-Base/efectos de los fármacos , Desoxicorticosterona/análogos & derivados , ATPasa Intercambiadora de Hidrógeno-Potásio/metabolismo , Riñón/efectos de los fármacos , Riñón/metabolismo , Mineralocorticoides/farmacología , Equilibrio Ácido-Base/fisiología , Animales , Presión Sanguínea/efectos de los fármacos , Presión Sanguínea/fisiología , Desoxicorticosterona/farmacología , Femenino , Hidrógeno/sangre , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Potasio/sangre , ARN Mensajero/metabolismo , Sodio/sangre , Aumento de Peso/efectos de los fármacos , Aumento de Peso/fisiologíaRESUMEN
The epithelial sodium channel (ENaC) mediates the fine-tuned regulation of external sodium (Na) balance. The circadian clock protein Period 1 (Per1) is an aldosterone-induced gene that regulates mRNA expression of the rate-limiting alpha subunit of ENaC (αENaC). In the present study, we examined the effect of Per1 on αENaC in the cortex, the site of greatest ENaC activity in the collecting duct, and examined the mechanism of Per1 action on αENaC. Compared to wild type mice, Per1 knockout mice exhibited a 50% reduction of steady state αENaC mRNA levels in the cortex. Importantly, siRNA-mediated knockdown of Per1 decreased total αENaC protein levels in mpkCCD(c14) cells, a widely used model of the murine cortical collecting duct (CCD). Per1 regulated basal αENaC expression and participated in the aldosterone-mediated regulation of αENaC in mpkCCD(c14) cells. Because circadian clock proteins mediate their effects as part of multi-protein complexes at E-box response elements in the promoters of target genes, the ability of Per1 to interact with these sequences from the αENaC promoter was tested. For the first time, we show that Per1 and Clock are present at an E-box response element found in the αENaC promoter. Together these data support an important role for the circadian clock protein Per1 in the direct regulation of αENaC transcription and have important implications for understanding the role of the circadian clock in the regulation of renal function.
Asunto(s)
Canales Epiteliales de Sodio/genética , Regulación de la Expresión Génica , Proteínas Circadianas Period/fisiología , Aldosterona/farmacología , Animales , Línea Celular , Elementos E-Box/efectos de los fármacos , Canales Epiteliales de Sodio/metabolismo , Regulación de la Expresión Génica/efectos de los fármacos , Túbulos Renales Colectores/efectos de los fármacos , Túbulos Renales Colectores/metabolismo , Ratones , Ratones Noqueados , Modelos Biológicos , Proteínas Circadianas Period/genética , Proteínas Circadianas Period/metabolismo , Regiones Promotoras Genéticas , Unión Proteica/fisiología , Transcripción Genética/efectos de los fármacos , Transcripción Genética/genéticaRESUMEN
PURPOSE OF REVIEW: We integrate recent evidence that demonstrates the importance of the gastric (HKalpha1) and nongastric (HKalpha2)-containing hydrogen potassium adenosine triphosphatases (H,K-ATPases) on physiological function and their role in potassium (K), sodium (Na), and acid-base balance. RECENT FINDINGS: Previous studies focused on the primary role of H,K-ATPases as a mechanism of K conservation during states of K deprivation. Both isoforms function in H secretion and K absorption in vivo during K deprivation, but recent findings show that these pumps also function in acid secretion in animals fed normal K-replete diets. The complicated pharmacological inhibition of both pumps is reviewed. Interestingly, HKalpha2-null mice have a reduced expression and activity of the renal epithelial Na channel alpha subunit in the colon. When the human nongastric isoform was studied in a heterologous expression system with its cognate beta subunit (NaKbeta1), the pump exhibited substantial Na affinity at the 'K'-binding site. Evidence cited herein raises the possibility that either directly or indirectly the renal HKalpha2-containing H,K-ATPase may affect Na balance. SUMMARY: Both H,K-ATPase isoforms are active in normal animals and not just under conditions of K depletion. The possibility that either one or both isoforms contribute to Na absorption, particularly in humans, raises important clinical implications for these pumps in the kidney.
Asunto(s)
ATPasa Intercambiadora de Hidrógeno-Potásio/fisiología , Riñón/enzimología , Acidosis/enzimología , Animales , ATPasa Intercambiadora de Hidrógeno-Potásio/análisis , Humanos , Transporte Iónico , Deficiencia de Potasio/enzimología , Sodio/metabolismoRESUMEN
In the collecting duct (CD), H-K-ATPases function in cation reabsorption and H secretion. This study evaluated H-K-ATPase-mediated H secretion along the mouse CD, measured as EIPA- and luminal bafilomycin A(1)-insensitive intracellular pH (pH(i)) recovery from acute H loading (NH(4)) using BCECF. pH(i) recovery was measured in 1) microperfused cortical, outer medullary, and inner medullary CDs (CCD, OMCD, and IMCD) from C57BL/6J mice fed a normal diet and 2) common murine CD cell lines. H-K-ATPase activity along the native, microperfused CD was greatest in the CCD, less in the OMCD, and least in the IMCD (0.10 +/- 0.02, 0.04 +/- 0.01, and 0.01 +/- 0.002 U/min, respectively). H-K-ATPase activity was 0.30 +/- 0.03 and 0.26 +/- 0.03 in A- and B-type ICs, respectively, and was sensitive to Sch-28080 or ouabain. pH(i) recovery was greatest in the OMCD(1) cell line (0.25 +/- 0.01) and less in mpkCCD(c14) (0.17 +/- 0.01), mIMCD-K2 (0.12 +/- 0.01), and mIMCD-3 (0.05 +/- 0.01) cells. EIPA inhibited the majority of pH(i) recovery in these cells (100%, 64%, 75%, and 80% in mpkCCD(c14), OMCD(1), mIMCD-K2, and mIMCD-3, respectively). In OMCD(1) cells, where EIPA-insensitive pH(i) recovery was greatest, H-K-ATPase activity was 0.10 +/- 0.01 and was significantly inhibited (80%) by Sch-28080. We conclude that 1) H-K-ATPase-mediated H secretion in the native mouse CD is greatest in the ICs of the CCD, 2) A- and B-type ICs possess HKalpha(1) and HKalpha(2) H-K-ATPase activity, and 3) the OMCD(1) cell line best exhibits H-K-ATPase.
Asunto(s)
Ácidos/metabolismo , ATPasa Intercambiadora de Hidrógeno-Potásio/metabolismo , Túbulos Renales Colectores/metabolismo , Animales , Línea Celular , Inhibidores Enzimáticos/farmacología , Femenino , ATPasa Intercambiadora de Hidrógeno-Potásio/genética , Concentración de Iones de Hidrógeno , Imidazoles/farmacología , Técnicas In Vitro , Membranas Intracelulares/metabolismo , Isoenzimas/genética , Corteza Renal/citología , Médula Renal/citología , Túbulos Renales Colectores/citología , Macrólidos/farmacología , Ratones , Ratones Endogámicos C57BL , Ouabaína/farmacología , Perfusión/métodos , Inhibidores de la Bomba de Protones , ARN Mensajero/metabolismo , Distribución TisularRESUMEN
The H(+)-K(+)-ATPases are ion pumps that use the energy of ATP hydrolysis to transport protons (H(+)) in exchange for potassium ions (K(+)). These enzymes consist of a catalytic alpha-subunit and a regulatory beta-subunit. There are two catalytic subunits present in the kidney, the gastric or HKalpha(1) isoform and the colonic or HKalpha(2) isoform. In this review we discuss new information on the physiological function, regulation, and structure of the renal H(+)-K(+)-ATPases. Evaluation of enzymatic functions along the nephron and collecting duct and studies in HKalpha(1) and HKalpha(2) knockout mice suggest that the H(+)-K(+)-ATPases may function to transport ions other than protons and potassium. These reports and recent studies in mice lacking both HKalpha(1) and HKalpha(2) suggest important roles for the renal H(+)-K(+)-ATPases in acid/base balance as well as potassium and sodium homeostasis. Molecular modeling studies based on the crystal structure of a related enzyme have made it possible to evaluate the structures of HKalpha(1) and HKalpha(2) and provide a means to study the specific cation transport properties of H(+)-K(+)-ATPases. Studies to characterize the cation specificity of these enzymes under different physiological conditions are necessary to fully understand the role of the H(+)-K(+) ATPases in renal physiology.
Asunto(s)
ATPasa Intercambiadora de Hidrógeno-Potásio/química , ATPasa Intercambiadora de Hidrógeno-Potásio/fisiología , Riñón/enzimología , Equilibrio Ácido-Base/fisiología , Animales , Transporte Biológico/fisiología , ATPasa Intercambiadora de Hidrógeno-Potásio/genética , Riñón/fisiología , Ratones , Ratones Noqueados , Modelos Animales , Sodio/metabolismoRESUMEN
The mineralocorticoid aldosterone is a major regulator of sodium transport in target epithelia and contributes to the control of blood pressure and cardiac function. It specifically functions to increase renal absorption of sodium from tubular fluid via regulation of the alpha subunit of the epithelial sodium channel (alphaENaC). We previously used microarray technology to identify the immediate transcriptional targets of aldosterone in a mouse inner medullary collecting duct cell line and found that the transcript induced to the greatest extent was the circadian clock gene Period 1. Here, we investigated the role of Period 1 in mediating the downstream effects of aldosterone in renal cells. Aldosterone treatment stimulated expression of Period 1 (Per1) mRNA in renal collecting duct cell lines and in the rodent kidney. RNA silencing of Period 1 dramatically decreased expression of mRNA encoding alphaENaC in the presence or absence of aldosterone. Furthermore, expression of alphaENaC-encoding mRNA was attenuated in the renal medulla of mice with disruption of the Per1 gene, and these mice exhibited increased urinary sodium excretion. Renal alphaENaC-encoding mRNA was expressed in an apparent circadian pattern, and this pattern was dramatically altered in mice lacking functional Period genes. These results suggest a role for Period 1 in the regulation of the renal epithelial sodium channel and more broadly implicate the circadian clock in control of sodium balance.
Asunto(s)
Canales Epiteliales de Sodio/genética , Regulación de la Expresión Génica , Péptidos y Proteínas de Señalización Intracelular/fisiología , Riñón/metabolismo , Aldosterona/farmacología , Animales , Células Cultivadas , Ritmo Circadiano , Perfilación de la Expresión Génica , Regulación de la Expresión Génica/efectos de los fármacos , Péptidos y Proteínas de Señalización Intracelular/genética , Masculino , Ratones , Proteínas Circadianas Period , ARN Mensajero/análisis , Ratas , Ratas Sprague-Dawley , Receptores de Glucocorticoides/fisiología , Receptores de Mineralocorticoides/fisiología , Sodio/orinaRESUMEN
Aldosterone and endothelin-1 (ET-1) act on collecting duct cells of the kidney and are important regulators of renal sodium transport and cardiovascular physiology. We recently identified the ET-1 gene (edn1) as a novel aldosterone-induced transcript. However, aldosterone action on edn1 has not been characterized at the present time. In this report, we show that aldosterone stimulated edn1 mRNA in acutely isolated rat inner medullary collecting duct cells ex vivo and ET-1 peptide in rat inner medulla in vivo. Aldosterone induction of edn1 mRNA occurred in cortical, outer medullary, and inner medullary collecting duct cells in vitro. Inspection of the edn1 promoter revealed two putative hormone response elements. Levels of heterogeneous nuclear RNA synthesis demonstrated that edn1 mRNA stimulation occurred at the level of transcription. RNA knockdowns corroborated pharmacological studies and demonstrated both mineralocorticoid receptor and glucocorticoid receptor participated in this response. Aldosterone resulted in dose-dependent nuclear translocation and binding of mineralocorticoid receptor and glucocorticoid receptor to the edn1 hormone response elements. Hormone receptors mediated the association of chromatin remodeling complexes, histone modification, and RNA polymerase II at the edn1 promoter. Direct interaction between aldosterone and ET-1 has important implications for renal and cardiovascular function.
Asunto(s)
Aldosterona/fisiología , Endotelina-1/genética , Receptores de Glucocorticoides/metabolismo , Receptores de Mineralocorticoides/metabolismo , Transporte Activo de Núcleo Celular , Animales , Médula Renal , Túbulos Renales Colectores , Regiones Promotoras Genéticas , Unión Proteica , ARN Mensajero , Ratas , Secuencias Reguladoras de Ácidos NucleicosRESUMEN
Humans are intermittently exposed to large variations in potassium intake, which range from periods of fasting to ingestion of potassium-rich meals. These fluctuations would abruptly alter plasma potassium concentration if not for rapid mechanisms, primarily in skeletal muscle and the liver, that buffer the changes in plasma potassium concentration by means of transcellular potassium redistribution and feedback control of renal potassium excretion. However, buffers have capacity limits, and even robust feedback control mechanisms require that the perturbation occur before feedback can initiate corrective action. In contrast, feedforward control mechanisms sense the effect of disturbances on the system's homeostasis. This review highlights recent experimental insights into the participation of feedback and feedforward control mechanisms in potassium homeostasis. New data make clear that feedforward homeostatic responses activate when decreased potassium intake is sensed, even when plasma potassium concentration is still within the normal range and before frank hypokalemia ensues, in addition to the classic feedback activation of renal potassium conservation when plasma potassium concentration decreases. Given the clinical importance of dyskalemias in patients, these novel experimental paradigms invite renewed clinical inquiry into this important area.