(Na+ + K+)-ATPase is a target for phosphoinositide 3-kinase/protein kinase B and protein kinase C pathways triggered by albumin.

In recent decades, evidence has confirmed the crucial role of albumin in the progression of renal disease. However, the possible role of signaling pathways triggered by physiologic concentrations of albumin in the modulation of proximal tubule (PT) sodium reabsorption has not been considered. In the present work, we have shown that a physiologic concentration of albumin increases the expression of the α1 subunit of (Na(+) + K(+))-ATPase in LLC-PK1 cells leading to an increase in enzyme activity. This process involves the sequential activation of PI3K/protein kinase B and protein kinase C pathways promoting inhibition of protein kinase A. This integrative network is inhibited when albumin concentration is increased, similar to renal disease, leading to a decrease in the α1 subunit of (Na(+) + K(+))-ATPase expression. Together, the results indicate that variation in albumin concentration in PT cells has an important effect on PT sodium reabsorption and, consequently, on renal sodium excretion.

Role of estrogen and progesterone in the modulation of CNG-A1 and Na/K+-ATPase expression in the renal cortex.

The steroid hormones, estrogen and progesterone, are involved mainly in the control of female reproductive functions. Among other effects, estrogen and progesterone can modulate Na(+) reabsorption along the nephron altering the body's hydroelectrolyte balance. In this work, we analyzed the expression of cyclic nucleotide-gated channel A1 (CNG-A1) and α1 Na(+)/K(+)-ATPase subunit in the renal cortex and medulla of female ovariectomized rats and female ovariectomized rats subjected to 10 days of 17ß-estradiol benzoate (2.0 µg/kg body weight) and progesterone (1.7 mg/kg body weight) replacement. Na(+)/K(+) ATPase activity was also measured. Immunofluorescence localization of CNG-A1 in the cortex and medulla was performed in control animals. We observed that CNG-A1 is localized at the basolateral membrane of proximal and distal tubules. Female ovariectomized rats showed low expression of CNG-A1 and low expression and activity of Na(+)/K(+) ATPase in the renal cortex. When female ovariectomized rats were subjected to 17ß-estradiol benzoate replacement, normalization of CNG-A1 expression and Na(+)/K(+) ATPase expression and activity was observed. The replacement of progesterone was not able to recover CNG-A1 expression and Na(+)/K(+) ATPase expression at the control level. Only the activity of Na(+)/K(+) ATPase was able to be recovered at control levels in animals subjected to progesterone replacement. No changes in expression and activity were observed in the renal medulla. The expression of CNG-A1 is higher in cortex compared to medulla. In this work, we observed that estrogen and progesterone act in renal tissues modulating CNG-A1 and Na(+)/K(+) ATPase and these effects could be important in Na(+) and water balance.

Na(+)-ATPase in spontaneous hypertensive rats: possible AT(1) receptor target in the development of hypertension.

Clinical and experimental data show an increase in sodium reabsorption on the proximal tubule (PT) in essential hypertension. It is well known that there is a link between essential hypertension and renal angiotensin II (Ang II). The present study was designed to examine ouabain-insensitive Na(+)-ATPase activity and its regulation by Ang II in spontaneously hypertensive rats (SHR). We observed that Na(+)-ATPase activity was enhanced in 14-week-old but not in 6-week-old SHR. The addition of Ang II from 10(-12) to 10(-6) mol/L decreased the enzyme activity in SHR to a level similar to that obtained in WKY. The Ang II inhibitory effect was completely reversed by a specific antagonist of AT(2) receptor, PD123319 (10(-8) mol/L) indicating that a system leading to activation of the enzyme in SHR is inhibited by AT(2)-mediated Ang II. Treatment of SHR with losartan for 10 weeks (weeks 4-14) prevents the increase in Na(+)-ATPase activity observed in 14-week-old SHR. These results indicate a correlation between AT(1) receptor activation in SHR and increased ouabain-insensitive Na(+)-ATPase activity. Our results open new possibilities towards our understanding of the pathophysiological mechanisms involved in the increased sodium reabsorption in PT found in essential hypertension.

Changes in angiotensin receptors expression play a pivotal role in the renal damage observed in spontaneously hypertensive rats.

The renal renin-angiotensin system plays a central role in the development of hypertension. The aim of this work was to verify the expression of angiotensin II receptors AT(1)R and AT(2)R in the microsomal fraction of renal cortex and correlate this with the development of hypertension and renal damage in spontaneously hypertensive rats (SHR) using Wistar-Kyoto rats (WKY) as controls. AT(1)R expression increased (126%) and AT(2)R expression decreased (66%) in 4-wk-old SHR; AT(2) expression decreased in 14-wk-old SHR (61%) compared with respective age-matched WKY. These modifications were correlated to the increase in protein kinase C activity and decrease in protein kinase A activity. Four-week-old SHR showed large accumulations of macrophages in kidney glomerulus and the tubulointerstitial area, dense cortical collagen deposition, and arterial proliferative changes in the walls of arterioles and medium-sized vessels. Similar modifications were also observed in 14-wk-old SHR. Four-week-old SHR treated with losartan (30 mg·kg(-1)·day(-1)) or hydralazine (15 and 30 mg·kg(-1)·day(-1)) by gavage for 10 wk did not develop hypertension. The decrease in AT(2)R expression and renal damage observed in SHR remained even after treatment with hydralazine. On the other hand, losartan treatment prevented the modifications observed in 14-wk-old SHR, indicating that renal injuries are caused specifically by AT(1) rather than an increase in blood pressure. Our results indicate that the imbalance in AT(1)R and AT(2)R expression is associated with an inflammatory process that contributes to renal injury in adult SHR and to the development of hypertension.

Ceramide-activated protein kinases A and C zeta inhibit kidney proximal tubule cell Na(+)-ATPase.

The basolateral membranes of kidney proximal tubule cells have (Na(+)+K(+))-ATPase and Na(+)-ATPase activities, involved in Na(+) reabsorption. We showed that ceramide (Cer) modulates protein kinase A (PKA) and protein kinase C (PKC), which are involved in regulating ion transporters. Here we show that ceramide, promotes 60% inhibition of Na(+)-ATPase activity (I(50) approximately 100nM). This effect was completely reversed by inhibiting PKA but did not involve the classic PKC signaling pathway. In these membranes we found the Cer-activated atypical PKC zeta (PKCzeta) isoform. When PKCzeta is inhibited, Cer ceases to inhibit the Na(+)-ATPase, allowing the cAMP/PKA signaling pathway to recover its stimulatory effect on the pump. There were no effects on the (Na(+)+K(+))-ATPase. These results reveal Cer as a potent physiological modulator of the Na(+)-ATPase, participating in a regulatory network in kidney cells and counteracting the stimulatory effect of PKA via PKCzeta.

Na(+)-ATPase and protein kinase C are targets to 1-O-hexadecylphosphocoline (miltefosine) in Trypanosoma cruzi.

Miltefosine has been shown to be a very active compound against Trypanosoma cruzi. Here, we evaluated the effects of miltefosine on the activity of the Na(+)-ATPase and protein kinase C (PKC) present in the plasma membrane of T. cruzi. Furosemide (2mM), a specific inhibitor of Na(+)-ATPase, abolished the growth of T. cruzi showing a crucial role of this enzyme to parasite growth. Miltefosine inhibited the Na(+)-ATPase activity with IC(50)=18+/-5 microg mL(-1). This effect was shown to be reversible, dependent on the pH and Ca(2+). The inhibition was not observed when the membranes were solubilized with 0.1% deoxycholate, suggesting that the interaction between the enzyme and membrane phospholipids might be important for the drug effect. Miltefosine also inhibited the parasite PKC activity, but through a Na(+)-ATPase-independent way. Altogether the results indicate that miltefosine inhibits T. cruzi growth through, at least in part, the inhibition of both Na(+)-ATPase and PKC activities.

Inhibition of renal Na+-ATPase activity by inosine is mediated by A1 receptor-induced inhibition of the cAMP signaling pathway.

We have previously demonstrated that adenosine is deaminated to inosine in the isolated basolateral membrane (BLM) of kidney proximal tubules. This work investigates the possible effect of inosine on proximal tubule Na(+)-ATPase activity. Inosine reduced Na(+)-ATPase activity by 70%. This effect of inosine was completely attenuated by 10(-8) M DPCPX, an A(1) receptor-selective antagonist, but it was not affected by either 10(-8) M DMPX or 10(-7) M MRS1523, A(2) and A(3) receptor-selective antagonists, respectively. The inhibitory effect of inosine was blocked by: (1) 10(-6) M GDPbetaS, a trimeric G protein inhibitor; (2) 1microg/ml pertussis toxin, a Gi protein inhibitor; (3) 10(-6) M forskolin, an adenylyl cyclase activator; (4) 10(-9) M cholera toxin, a Gs protein activator; (5) 10(-6)M cAMP. Our results demonstrate that the inhibitory effect of inosine on the sodium pump is mediated by the A(1) receptor/Gi/cAMP pathway.

Adenosine deamination to inosine in isolated basolateral membrane from kidney proximal tubule: implications for modulation of the membrane-associated protein kinase A.

In this work, the metabolism of adenosine by isolated BLM associated-enzymes and the implications of this process for the cAMP-signaling pathway are investigated. Inosine was identified as the major metabolic product, suggesting the presence of adenosine deaminase (ADA) activity in the BLM. This was confirmed by immunoblotting and ADA-specific enzyme assay. Implications for the enzymatic deamination of adenosine on the receptor-modulated cAMP-signaling pathway were also investigated. We observed that inosine induced a 2-fold increase in [(35)S] GTPgammaS binding to the BLM and it was inhibited by 10(-6)M DPCPX, an A(1) receptor-selective antagonist. Inosine (10(-7)M) inhibited protein kinase A activity in a DPCPX-sensitive manner. Molecular association between ADA and G(alphai-3) protein-coupled A(1) receptor was demonstrated by co-immunoprecipitation assay. These data show that adenosine is deaminated by A(1) receptor-associated ADA to inosine, which in turn modulates PKA in the BLM through A(1) receptor-mediated inhibition of adenylyl cyclase.

A importância da qualidade de vida em pacientes hipertensos / The importance of quality life in hipertensive patients

Objetivo: Avaliar a qualidade de vida dos pacientes hipertensos, que realizam tratamento na Clínica da Família Olímpia Esteves. Metodologia: O trabalho foi realizado em etapas: captação, entrevista e aplicação de instrumento para a avaliação da qualidade de vida, o Formulário Abreviado de Avaliação em Saúde, SF-36. Resultados: O SF36 é um instrumento para mensurar aspectos multidimensionais da saúde, englobando 8 domínios: capacidade funcional, aspecto físico, dor, estado geral de saúde, vitalidade, aspecto social, aspecto emocional e saúde mental. Foram avaliados 34 pacientes: 85,29% mulheres; 14,71% homens; 61,32% com mais de 60 anos; 35,29% sofreram acidente vascular cerebral e 29,41% têm diabetes. A média dos domínios do SF-36 com menor valor obtido foram dor (36,9), limitação por aspecto físico (48,4), limitação por aspecto emocional (49,9) e capacidade funcional (53,8). Verificou - se que pacientes com comorbidades associadas apresentam maior prejuízo na qualidade de vida. Conclusão: Este estudo aponta que pacientes hipertensos sofrem a influência de diversas limitações nas atividades de vida diária, podendo acarretar prejuízos significativos nos domínios de aspectos mentais. Portanto, a ampliação do cuidado na rede de atenção básica, pode ser uma estratégia para melhoria da qualidade de vida do paciente hipertenso.

Objective: To evaluate the quality of life of hypertensive patients that undergoing treatment at the Clinic of Olympia Family Esteves. Methodology: The study was carried out in stages: collection, interview and application tool for evaluating the quality of life, Short Form Health Evaluation, SF-36. Results: The SF-36 is an instrument for measuring multidimensional aspects of health, covering 8 domains: functional capacity, physical aspects, pain, general health, vitality, social aspects, emotional aspects and mental health. 34 patients were evaluated: 85.29% women; 14.71% men; 61.32% over 60 years; 35.29% had stroke and 29.41% have diabetes. The average of the SF-36 with lower value obtained were pain (36.9), role limitations due to physical appearance (48.4), role limitations due to emotional aspects (49.9) and functional capacity (53.8). It was found that patients with associated comorbidities have greater impairment in quality of life. Conclusion: This study shows that hypertensive patients are influenced by a number of limitations in activities of daily living and may cause significant damage in the fields of mental aspects. Therefore, the expansion of care in the primary care network, may be a strategy to improve the hypertensive patient's quality of life.

Ceramide is a potent activator of plasma membrane Ca2+-ATPase from kidney-promixal tubule cells with protein kinase A as an intermediate.

The kidney-proximal tubules are involved in reabsorbing two-thirds of the glomerular ultrafiltrate, a key Ca(2+)-modulated process that is essential for maintaining homeostasis in body fluid compartments. The basolateral membranes of these cells have a Ca(2+)-ATPase, which is thought to be responsible for the fine regulation of intracellular Ca(2+) levels. In this paper we show that nanomolar concentrations of ceramide (Cer(50) = 3.5 nm), a natural product derived from sphingomyelinase activity in biological membranes, promotes a 50% increase of Ca(2+)-ATPase activity in purified basolateral membranes. The stimulatory effect of ceramide occurs through specific and direct (cAMP-independent) activation of a protein kinase A (blocked by 10 nm of the specific inhibitor of protein kinase A (PKA), the 5-22 peptide). The activation of PKA by ceramide results in phosphorylation of the Ca(2+)-ATPase, as detected by an anti-Ser/Thr specific PKA substrate antibody. It is observed a straight correlation between increase of Ca(2+)-ATPase activity and PKA-mediated phosphorylation of the Ca(2+) pump molecule. Ceramide also stimulates phosphorylation of renal Ca(2+)-ATPase via protein kinase C, but stimulation of this pathway, which inhibits the Ca(2+) pump in kidney cells, is counteracted by the ceramide-triggered PKA-mediated phosphorylation. The potent effect of ceramide reveals a new physiological activator of the plasma membrane Ca(2+)-ATPase, which integrates the regulatory network of glycerolipids and sphingolipids present in the basolateral membranes of kidney cells.