RESUMO
The growing molecular identification of renal transporter genes is revealing that alternative splicing is common among transporters. In this paper, I review the physiological consequences of alternative splicing in some genes encoding renal transporters in which spliced isoforms have recently been identified. In some cases, the spliced isoforms resulted in nonfunctional proteins, which, however, possess a dominant negative effect on the cotransporter function, suggesting that the presence of such isoforms can be important in the functional regulation of the transporter. In most transporter genes, however, the spliced isoforms have been shown to be functional, resulting in a variety of physiological consequences, including, for example, changes in the polarization of isoforms to the apical or basolateral membrane, changes in pharmacological or kinetic properties, and changes in tissue distribution or intrarenal localization. In some cases, although the spliced isoform is functional, the consequence of splicing is still unknown. Different regulation among isoforms is an interesting possibility. Thus the diversity of several renal transporters is enhanced by alternative splicing mechanisms.
Assuntos
Processamento Alternativo , Proteínas de Transporte/genética , Rim/química , Proteínas de Membrana Transportadoras , Transportadores de Ânions Orgânicos Dependentes de Sódio , Simportadores , Animais , Humanos , Glicoproteínas de Membrana/genética , Proteínas de Transporte de Monossacarídeos/genética , Proteínas de Transporte de Fosfato/genética , Simportadores de Sódio-Bicarbonato/genética , Trocadores de Sódio-Hidrogênio/genética , Transportadores de Sulfato , Transportadores de UreiaRESUMO
The K-Cl cotransporters (KCCs) have a broad range of physiological roles, in a number of cells and species. We report here that Xenopus laevis oocytes express a K-Cl cotransporter with significant functional and molecular similarity to mammalian KCCs. Under isotonic conditions, defolliculated oocytes exhibit a Cl(-)-dependent (86)Rb(+) uptake mechanism after activation by the cysteine-reactive compounds N-ethylmaleimide (NEM) and mercuric chloride (HgCl(2)). The activation of this K-Cl cotransporter by cell swelling is prevented by inhibition of protein phosphatase-1 with calyculin A; NEM activation of the transporter was not blocked by phosphatase inhibition. Kinetic characterization reveals apparent values for the Michaelis-Menten constant of 27.7 +/- 3.0 and 15.4 +/- 4.7 mM for Rb(+) and Cl(-), respectively, with an anion selectivity for K(+) transport of Cl(-) = PO(4)(3-) = Br(-) > I(-) > SCN(-) > gluconate. The oocyte K-Cl cotransporter was sensitive to several inhibitors, including loop diuretics, with apparent half-maximal inhibition values of 200 and 500 microM for furosemide and bumetanide, respectively. A partial cDNA encoding the Xenopus K-Cl cotransporter was cloned from oocyte RNA; the corresponding transcript is widely expressed in Xenopus tissues. The predicted COOH-terminal protein fragment exhibited particular homology to the KCC1/KCC3 subgroup of the mammalian KCCs, and the functional characteristics are the most similar to those of KCC1 (Mercado A, Song L, Vazquez N, Mount DB, and Gamba G. J Biol Chem 275: 30326--30334, 2000).
Assuntos
Proteínas de Transporte/metabolismo , Oócitos/metabolismo , Simportadores , Xenopus laevis/metabolismo , Sequência de Aminoácidos/genética , Animais , Ânions/metabolismo , Proteínas de Transporte/antagonistas & inibidores , Proteínas de Transporte/genética , Feminino , Cinética , Dados de Sequência Molecular , RNA Mensageiro/metabolismo , Homologia de Sequência de Aminoácidos , Xenopus laevis/genética , Cotransportadores de K e Cl-RESUMO
BACKGROUND: Dialysate protein loss is involved in the etiology of hypoalbuminemia and malnutrition on continuous ambulatory peritoneal dialysis (CAPD). Patients with high peritoneal membrane permeability had the lowest serum albumin (Alb) and highest dialysate protein concentrations and achieved higher small solute dialysis/plasma equilibration in a shorter time than patients with low peritoneal transport. The aim of this prospective crossover study was to evaluate whether protein loss might be decreased in patients with high peritoneal permeability on short dwell-time (DT) peritoneal dialysis. METHODS: Five high and nine high-average peritoneal transport patients were subjected to the following sequential dialysis schemes (four exchanges/day, glucose 1.5%): scheme A, three daytime exchanges (4-6 h DT) and one nightly (8-12 h DT) for 2-3 days, scheme B, 3-h DT each and dry peritoneum at night during 5 days, a wash-out period similar to scheme A, and scheme C, 2-h DT each and dry peritoneum the remainder of day and night during 5 days. Dialysate Alb, IgG, IgA, and IgM losses and adequacy of dialysis were evaluated at the end of each scheme. RESULTS: Dialysate IgM was not detected. All protein losses were reduced with the short DT dialysis schemes; however, dialysis CCl and KT/V(urea) were also decreased. In patients with high peritoneal transport type, the 3-h DT dialysis scheme achieved a reduction in Alb loss without significant reduction of adequacy of dialysis. CONCLUSIONS: Peritoneal Alb, IgG, and IgA losses are significantly reduced in patients with high peritoneal permeability on short dwell-time dialysis and extended dry periods. However, a reduction of dialysis contribution to small solute clearances was also observed, Three-hour dwell-time dialysis may be particularly useful in patients with high peritoneal transport type, as it tends to reduce peritoneal protein loss without notably reducing adequacy of dialysis.
Assuntos
Diálise Peritoneal Ambulatorial Contínua/efeitos adversos , Peritônio/metabolismo , Proteínas/metabolismo , Adulto , Estudos de Coortes , Feminino , Humanos , Imunoglobulina M/metabolismo , Masculino , Pessoa de Meia-Idade , PermeabilidadeRESUMO
PURPOSE: To study the effect of aminoguanidine (AMG), an inhibitor of nitric oxide production, on the ocular infection of Balb/c mice with herpes simplex virus (HSV) type 1 strain F and HSV-2 strain G. METHODS: Animals were treated with different amounts of AMG (0.5, 0.1, and 0.05 mg/mouse) by topical application in the eye from postinfection (PI) days -2 through +5, considering 0 the day of infection. At different PI days, development of herpetic keratitis was evaluated in treated and control mice. RESULTS: Treated animals showed a dose-dependent increase in ocular disease after viral infection, compared with control animals. Viral titers in ocular washings were higher in AMG-treated mice (PI day 2, HSV-1: AMG 0.5 mg, 1.3 x 10(3) plaque-forming units (PFU)/ml; control, 0. 22 x 10(2) PFU/ml, P < 0.025). At PI day 3, control corneas had only scattered inflammatory cells, whereas those from treated animals showed a conspicuous infiltrate consisting primarily of neutrophils. Viral titers were also higher in brains of treated mice. These animals died earlier and in a greater proportion than control animals (percentage of mortality, PI day 12, HSV-1: AMG 0.5 mg, 40% +/- 4%; control, 18% +/- 3%, P < 0.05). CONCLUSIONS: These data indicate an inhibitory effect of nitric oxide on HSV ocular infection.
Assuntos
Córnea/efeitos dos fármacos , Inibidores Enzimáticos/uso terapêutico , Guanidinas/uso terapêutico , Ceratite Herpética/tratamento farmacológico , Óxido Nítrico Sintase/antagonistas & inibidores , Administração Tópica , Animais , Córnea/enzimologia , Córnea/virologia , DNA Viral/análise , Progressão da Doença , Relação Dose-Resposta a Droga , Herpesvirus Humano 1/isolamento & purificação , Herpesvirus Humano 1/fisiologia , Herpesvirus Humano 2/isolamento & purificação , Herpesvirus Humano 2/fisiologia , Ceratite Herpética/patologia , Ceratite Herpética/virologia , Camundongos , Camundongos Endogâmicos BALB C , Óxido Nítrico Sintase/genética , Óxido Nítrico Sintase/metabolismo , Soluções Oftálmicas , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Gânglio Trigeminal/virologiaRESUMO
BACKGROUND: We have previously shown that the prevalence of hepatitis associated with the hepatitis C virus (HCV) in patients with end stage renal disease in our institution is 10.2%. However, quantification of viral RNA in plasma and its relation with clinical variables has never been studied in our patients. Thus, the aim of the present work was to quantify the HCV viral load in patients with ESRD in dialysis, and to correlate these values with the dialysis modality and the viral genotype. METHODS: We performed a transverse, prospective and comparative study in patients with HCV infection in hemodialysis, continuous ambulatory peritoneal dialysis and patients in peritoneal dialysis, but with history of hemodialysis. Viral load was quantified with RT-PCR by using a commercial kit known as Amplicor HCV 2.0. Clinical variables studied were: age, gender, end stage renal disease etiology, modality and time in dialysis, transfusions, serum albumin, aminotransferases, blood urea nitrogen, and serum creatinine. RESULTS: Twenty four patients in dialysis with HCV infection entered into the study. Of these patients, 25% were on peritoneal dialysis, 29% on peritoneal dialysis with history of hemodialysis, and 46% were in hemodialysis. The average viral load (copies x 10(6)/mL) was 1.41 +/- 3.01. Viral load was lower in patients on peritoneal dialysis than in patients treated, or with history of hemodialysis (0.20 +/- 0.12 vs 2.04 +/- 0.88; p < 0.05). We observed no differences in viral load among patients with different viral genotypes. DISCUSSION: The average viral load of our patients in dialysis is lower than the levels usually observed in hepatitis C infected patients without end stage renal disease. The lower viral load in patients treated with peritoneal dialysis, and no history of hemodialysis, probably denotes lower risk of chronic liver disease in these subpopulation.
Assuntos
Hepacivirus/isolamento & purificação , Hepatite C/epidemiologia , Falência Renal Crônica/complicações , Adulto , Idoso , Estudos Transversais , Feminino , Genótipo , Hepacivirus/classificação , Hepacivirus/genética , Hepatite C/complicações , Hepatite C/transmissão , Hepatite C/virologia , Humanos , Falência Renal Crônica/terapia , Testes de Função Hepática , Masculino , México/epidemiologia , Pessoa de Meia-Idade , Diálise Peritoneal Ambulatorial Contínua/efeitos adversos , Prevalência , Estudos Prospectivos , RNA Viral/genética , RNA Viral/isolamento & purificação , Diálise Renal/efeitos adversos , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Reação Transfusional , Carga Viral , Viremia/epidemiologia , Viremia/virologiaRESUMO
In the absence of vasopressin, medullary thick ascending limb cells express a K(+)-independent, furosemide-sensitive Na(+)-Cl(-) cotransporter that is inhibited by hypertonicity. The murine renal specific Na(+)-K(+)-2 Cl(-) cotransporter gene (SLC12A1) gives rise to six alternatively spliced isoforms. Three feature a long COOH-terminal domain that encodes the butmetanide-sensitive Na(+)-K(+)-2 Cl(-) cotransporter (BSC1-9/NKCC2), and three with a short COOH-terminal domain, known as mBSC1-A4, B4, or F4 (19). Here we have determined the functional characteristics of mBSC1-A4, as expressed in Xenopus laevis oocytes. When incubated at normal oocyte osmolarity (approximately 200 mosmol/kgH(2)O), mBSC1-4-injected oocytes do not express significant Na(+) uptake over H(2)O-injected controls, and immunohistochemical analysis shows that the majority of mBSC1-4 protein is in the oocyte cytoplasm and not at the plasma membrane. In contrast, when mBSC1-4 oocytes are exposed to hypotonicity (approximately 100 mosmol/kgH(2)O), a significant increase in Na(+) uptake but not in (86)Rb(+) uptake is observed. The increased Na(+) uptake is Cl(-) dependent, furosemide sensitive, and cAMP sensitive but K(+) independent. Sodium uptake increases with decreasing osmolarity between 120 and 70 mosmol/kgH(2)O (r = 0.95, P < 0.01). Immunohistochemical analysis shows that in hypotonic conditions mBSC1-A4 protein is expressed in the plasma membrane. These studies indicate that the mBSC1-A4 isoform of the SLC12A1 gene encodes a hypotonically activated, cAMP- and furosemide-sensitive Na(+)-Cl(-) cotransporter. Thus it is possible that alternative splicing of the BSC1 gene could provide the molecular mechanism enabling the Na(+)-Cl(-)-to-Na(+)-K(+)-2Cl(-) switching in thick ascending limb cells.
Assuntos
Processamento Alternativo/fisiologia , Proteínas de Transporte/genética , Proteínas de Transporte/metabolismo , Diuréticos/farmacologia , Furosemida/farmacologia , Sulfonamidas , 1-Metil-3-Isobutilxantina/farmacologia , Animais , Transporte Biológico/efeitos dos fármacos , Transporte Biológico/fisiologia , Bumetanida/farmacologia , Proteínas de Transporte/química , Membrana Celular , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/antagonistas & inibidores , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Citosol/metabolismo , Inibidores Enzimáticos/farmacologia , Feminino , Expressão Gênica/fisiologia , Soluções Hipotônicas/farmacologia , Isomerismo , Isoquinolinas/farmacologia , Alça do Néfron/enzimologia , Mamíferos , Oócitos/fisiologia , Concentração Osmolar , Inibidores de Fosfodiesterase/farmacologia , Radioisótopos de Sódio/farmacocinética , Simportadores de Cloreto de Sódio-Potássio , Trítio , Xenopus laevisRESUMO
BACKGROUND/AIMS: Several lines of evidence support that the kidney is involved in the increase of arterial blood pressure, and some genetic studies suggest that the thiazide-sensitive Na+:Cl- cotransporter could be implicated in the development of hypertension. In the present study, we analyzed the Na+:Cl- cotransporter mRNA levels in the kidney during the development of hypertension in three experimental models. METHODS: The first model included 18 spontaneously hypertensive rats studied at 4, 10, and 16 weeks of age. The second model included 28 Wistar rats with two-kidney, one-clip Goldblatt hypertension studied at 7, 14, 21, and 28 days. The third model included 6 Wistar rats treated with N(G)-nitro-L-arginine methyl ester during 10 days. Respective controls were studied for all models. At the end of each experimental period, the systolic blood pressure was measured in the tail by plethysmography. Individual renal cortex total RNA was extracted, and the mRNA levels of the thiazide-sensitive Na+:Cl- cotransporter were assessed following a semiquantitative RT-PCR strategy. RESULTS: All experimental models developed systemic hypertension. However, the level of mRNA expression of the Na+:Cl- cotransporter did not change in any of the models studied as compared with their respective controls. CONCLUSION: Our results suggest that a change in mRNA levels of the thiazide-sensitive Na+:Cl- cotransporter is not associated with the development of hypertension in spontaneously hypertensive rats, in rats with renovascular hypertension, nor in rats with hypertension induced by nitric oxide synthesis inhibition.
Assuntos
Proteínas de Transporte/genética , Hipertensão/genética , Receptores de Droga/genética , Simportadores , Animais , Benzotiadiazinas , Proteínas de Transporte/metabolismo , Modelos Animais de Doenças , Diuréticos , Regulação da Expressão Gênica , Hipertensão/metabolismo , Hipertensão/fisiopatologia , Hipertensão Renovascular/genética , Hipertensão Renovascular/metabolismo , Hipertensão Renovascular/fisiopatologia , RNA Mensageiro/biossíntese , RNA Mensageiro/genética , Ratos , Ratos Endogâmicos SHR , Ratos Endogâmicos WKY , Ratos Wistar , Receptores de Droga/metabolismo , Inibidores de Simportadores de Cloreto de Sódio/metabolismo , Simportadores de Cloreto de Sódio , Membro 3 da Família 12 de Carreador de SolutoRESUMO
BACKGROUND: The present study was designed to know the clinical course of lupus nephritis and the risk factors associated with the development of end stage renal disease. METHODS: This a retrospective study performed in a cohort of 154 patients with biopsy proven lupus nephritis that were seen in our hospital between 1984 and 1990. The clinical records of all patients were reviewed in order to collect the following information at the time of the biopsy: age, sex, number and type of lupus criteria according with the American College of Reumathology, mean arterial pressure, serum creatinine, BUN, and albumin, as well as urinary protein excretion. The follow up was registered from the day the biopsy was performed to one of the following end points: end stage renal disease (defined as requirement of chronic dialysis), death or the end of study. All biopsies were analyzed by light microscopy to obtain the hystological subtype of lupus nephritis (WHO classification) and when type IV was diagnosed, the activity and chronicity indexes were also assessed. Kaplan-Meier survival tables were constructed. The association of clinical and laboratory variables with the development of end stage renal disease was obtained by log rank analysis. Variables obtained as significant were used to evaluate their individual impact using either the Cox multivariate proportional hazard method. RESULTS: Follow up was complete in 144 patients with a follow up time of 68 +/- 38 months. Ninety three patients were female with mean age of 28 +/- 9 years. At the time of the biopsy, renal manifestations had been present for 35 +/- 38 months and the number of lupus criteria per patient were 4 +/- 1. The clinical picture at the time of the biopsy was: nephrotic syndrome in 60%, non nephrotic proteinuria in 40%, and nephritic syndrome in only 2%. The hystological type of lupus nephritis was: I in 2%, II in 8%, III in 6%, IV in 71% and V in 11%. At the end of the study 28 patients developed end stage renal disease. For the whole group the survival of renal function was 85% at 70 months and 70% at 140 months. All, but one patient that developed end stage renal disease exhibited type IV nephropathy. In this subpopulation the mean activity and chronicity indexes were 8.5 +/- 3.5 and 3.1 +/- 2.4, respectively. By multivariate analysis the strongest predictors of end stage renal disease were the serum creatinine at the time of the biopsy, chronicity index, and age. The higher the serum creatinine and chronicity index at the time of biopsy, the higher the probability of developing end stage renal disease. CONCLUSIONS: We conclude that the clinical course of lupus nephritis in our population is similar to that seen in other series. The variables indicating advanced renal disease, such as high serum creatinine and chronicity index, were the strongest predictors of end stage renal disease.
Assuntos
Falência Renal Crônica/epidemiologia , Falência Renal Crônica/etiologia , Nefrite Lúpica/complicações , Adulto , Feminino , Humanos , Masculino , Prognóstico , Estudos Retrospectivos , Fatores de RiscoRESUMO
Cyclosporine toxicity mainly affects kidney and liver function. We have previously shown that cyclosporine nephrotoxicity alters kidney nitric oxide synthase mRNA pattern of expression. To determine if nitric oxide synthase expression changes are mediated directly by cyclosporine or by secondary hemodynamic alterations induced by cyclosporine, we evaluated if these effects are tissue specific and if nifedipine-induced vasodilation prevents these alterations. Uninephrectomized Wistar rats treated for 7 days with olive oil, cyclosporine (30 mg/kg), nifedipine (3 mg/kg), and nifedipine+cyclosporine were studied. In vehicle and cyclosporine groups, the gene expression of the neuronal, inducible, and endothelial nitric oxide synthases in cerebellum, heart, intestine, liver, renal cortex, and medulla was evaluated. The administration of cyclosporine was associated with nephrotoxicity and hepatotoxicity, increased endothelial nitric oxide synthase mRNA levels in renal cortex and liver, and a decrease in inducible nitric oxide synthase and neuronal nitric oxide synthase in renal medulla. The mRNA levels of the 3 nitric oxide synthase isoforms were not affected in any other tissue. Nifedipine did not alter nitric oxide synthase expression in the control group but prevented changes associated with cyclosporine. These results suggest that cyclosporine-induced changes in the pattern of expression of the nitric oxide synthases may be secondary to its hemodynamic effects.
Assuntos
Ciclosporina/farmacologia , Nifedipino/farmacologia , Óxido Nítrico Sintase/efeitos dos fármacos , Óxido Nítrico Sintase/genética , RNA Mensageiro/efeitos dos fármacos , Animais , Peso Corporal/efeitos dos fármacos , Ciclosporina/toxicidade , Taxa de Filtração Glomerular/efeitos dos fármacos , Gliceraldeído-3-Fosfato Desidrogenases/metabolismo , Isoenzimas/genética , Isoenzimas/metabolismo , Córtex Renal/efeitos dos fármacos , Córtex Renal/enzimologia , Medula Renal/efeitos dos fármacos , Medula Renal/enzimologia , Fígado/efeitos dos fármacos , Fígado/enzimologia , Testes de Função Hepática , Masculino , Nefrectomia , Óxido Nítrico Sintase/metabolismo , Óxido Nítrico Sintase Tipo I , Óxido Nítrico Sintase Tipo II , Óxido Nítrico Sintase Tipo III , Especificidade de Órgãos , RNA Mensageiro/metabolismo , Ratos , Ratos WistarRESUMO
BACKGROUND: The prevalence of hepatitis C in patients with end stage renal disease, under renal replacement therapy either with hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD), is higher than in the general population. The prevalence of hepatitis C in patients under dialysis, however, is unknown in Mexico. Thus, the major goals of the present study were to determine the prevalence of hepatitis C in our patients on dialysis, and the risk factors associated with it. METHODS: We performed a cross-sectional and comparative study in patients under dialysis in three hospital centers in the south of Mexico City. For every patient we evaluated: age, gender, etiology of the renal failure, modality and time in dialysis, transfusion and surgical history, serum albumin, aminotranferases, BUN, and serum creatinine. The presence of hepatitis C was assessed by ELISA II and qualitative RT-PCR in blood samples. In all patients diagnosed as having hepatitis C, RT-PCR to amplified part of the virus genome was also carried out in the dialysis fluid. RESULTS: We studied 235 dialysis patients that were classified according to their dialysis modality in: 132 patients under CAPD, 17 under CAPD and history of HD (PD/HD) and 86 under HD. The time under dialysis was different between the study groups: CAPD 29.6 +/- 22.3 months, PD/HD 39 +/- 42.3 and HD 14.2 +/- 15.6 (p < 0.01). The presence of hepatitis C was detected in 24 of the 235 patients, for a global prevalence of 10.2%. In no case was viral RNA found in the dialysis fluid. The prevalence varied, however, according to the type of dialysis. It was in the CAPD group 4.5%, 12.7% in the HD group, and 41.1% in the PD/HD group (p < 0.001). The multivariate analysis showed that the risk factors for hepatitis C are transfusions before the year of 1991 (Odds Ratio = 6.4), and history of hepatitis (OR = 4.3). Since less patients are seen with transfusions before 1991, we constructed another model in which this variable was excluded. This new multivariate model showed that history of surgery (OR = 4.4), the use of HD as the dialysis modality (OR = 3.5), and prolonged time under dialysis (OR = 1.01) were all significantly associated with the presence of hepatitis. DISCUSSION: Our results show that the prevalence of hepatitis C is lower in our patients that the prevalence reported by many others (average of other countries 18.5%). Since we found a higher prevalence in HD than in CAPD, even with the lower time under dialysis in the HD group, it is possible that our lower overall prevalence is secondary to the fact that CAPD is the most frequent mode of dialysis in our country. We observed the highest prevalence in the PD/HD group, that is probably due to longer exposure to the risk factors. The association with transfusions before 1991 indicates that the infection was acquired in some patients before dialysis was started. Our results showed that the CAPD is the dialysis technique with lower risk of hepatitis C infection.
Assuntos
Hepatite C/epidemiologia , Hepatite C/etiologia , Falência Renal Crônica/complicações , Adulto , Estudos Transversais , Feminino , Humanos , Falência Renal Crônica/terapia , Masculino , Pessoa de Meia-Idade , Prevalência , Diálise RenalRESUMO
The thiazide-sensitive Na(+)-Cl(-) cotransporter (TSC) is the major pathway for salt reabsorption in the apical membrane of the mammalian distal convoluted tubule. When expressed in Xenopus laevis oocytes, rat TSC exhibits high affinity for both cotransported ions, with the Michaelis-Menten constant (K(m)) for Na(+) of 7.6 +/- 1.6 mM and for Cl(-) of 6.3 +/- 1.1 mM, and Hill coefficients for Na(+) and Cl(-) consistent with electroneutrality. The affinities of both Na(+) and Cl(-) were increased by increasing concentration of the counterion. The IC(50) values for thiazides were affected by both extracellular Na(+) and Cl(-). The higher the Na(+) or Cl(-) concentration, the lower the inhibitory effect of thiazides. Finally, rTSC function is affected by extracellular osmolarity. We propose a transport model featuring a random order of binding in which the binding of each ion facilitates the binding of the counterion. Both ion binding sites alter thiazide-mediated inhibition of transport, indicating that the thiazide-binding site is either shared or modified by both Na(+) and Cl(-).
Assuntos
Proteínas de Transporte/metabolismo , Receptores de Droga/metabolismo , Inibidores de Simportadores de Cloreto de Sódio/metabolismo , Inibidores de Simportadores de Cloreto de Sódio/farmacologia , Sódio/metabolismo , Simportadores , Animais , Bendroflumetiazida/metabolismo , Bendroflumetiazida/farmacologia , Sítios de Ligação/efeitos dos fármacos , Transporte Biológico/efeitos dos fármacos , Proteínas de Transporte/genética , Cloretos/metabolismo , Cloretos/farmacologia , Diuréticos , Hidroclorotiazida/metabolismo , Hidroclorotiazida/farmacologia , Concentração de Íons de Hidrogênio , Concentração Inibidora 50 , Cinética , Metolazona/metabolismo , Metolazona/farmacologia , Microinjeções , Modelos Biológicos , Oócitos/efeitos dos fármacos , Oócitos/metabolismo , Concentração Osmolar , Politiazida/metabolismo , Politiazida/farmacologia , Ratos , Receptores de Droga/genética , Sódio/farmacologia , Simportadores de Cloreto de Sódio , Membro 3 da Família 12 de Carreador de Soluto , XenopusRESUMO
The K(+)-Cl(-) cotransporters (KCCs) are members of the cation-chloride cotransporter gene family and fall into two phylogenetic subgroups: KCC2 paired with KCC4 and KCC1 paired with KCC3. We report a functional comparison in Xenopus oocytes of KCC1 and KCC4, widely expressed representatives of these two subgroups. KCC1 and KCC4 exhibit differential sensitivity to transport inhibitors, such that KCC4 is much less sensitive to bumetanide and furosemide. The efficacy of these anion inhibitors is critically dependent on the concentration of extracellular K(+), with much higher inhibition in 50 mm K(+) versus 2 mm K(+). KCC4 is also uniquely sensitive to 10 mm barium and to 2 mm trichlormethiazide. Kinetic characterization reveals divergent affinities for K(+) (K(m) values of approximately 25.5 and 17.5 mm for KCC1 and KCC4, respectively), probably due to variation within the second transmembrane segment. Although the two isoforms have equivalent affinities for Cl(-), they differ in the anion selectivity of K(+) transport (Cl(-) > SCN(-) = Br(-) > PO(4)(-3) > I(-) for KCC1 and Cl(-) > Br(-) > PO(4)(-3) = I(-) > SCN(-) for KCC4). Both KCCs express minimal K(+)-Cl(-) cotransport under isotonic conditions, with significant activation by cell swelling under hypotonic conditions. The cysteine-alkylating agent N-ethylmaleimide activates K(+)-Cl(-) cotransport in isotonic conditions but abrogates hypotonic activation, an unexpected dissociation of N-ethylmaleimide sensitivity and volume sensitivity. Although KCC4 is consistently more volume-sensitive, the hypotonic activation of both isoforms is critically dependent on protein phosphatase 1. Overall, the functional comparison of these cloned K(+)-Cl(-) cotransporters reveals important functional, pharmacological, and kinetic differences with both physiological and mechanistic implications.
Assuntos
Proteínas de Transporte/metabolismo , Cloretos/metabolismo , Potássio/metabolismo , Simportadores , Animais , Compostos de Bário/farmacologia , Transporte Biológico/efeitos dos fármacos , Bumetanida/farmacologia , Proteínas de Transporte/genética , Cloretos/farmacologia , Etilmaleimida/farmacologia , Furosemida/farmacologia , Humanos , Cinética , Toxinas Marinhas , Camundongos , Ácido Okadáico/farmacologia , Oócitos , Oxazóis/farmacologia , Fosfoproteínas Fosfatases/antagonistas & inibidores , Isoformas de Proteínas/metabolismo , Proteína Fosfatase 1 , Piretrinas/farmacologia , Proteínas Recombinantes/metabolismo , Rubídio/metabolismo , Tubarões , Xenopus laevis , Cotransportadores de K e Cl-RESUMO
UNLABELLED: Percutaneous renal biopsy is an invasive procedure that can result in major and minor complications. The objective of this study was to know the frequency and type of complications in relation with this procedure, as well as the efficacy to obtain enough material for diagnosis. METHODS: Retrospective study. We review the charts of patients to whom a percutaneous renal biopsy of native kidneys was done between January 1970 and March 1996. The following data were obtained: age, gender, clinical and histopathological diagnosis, complications associated with the procedure (minor: hematuria, local infections, hematoma; major: transfusions, severe infections, surgery, nephrectomy, arteriography, embolism and death). RESULTS: We analyzed 1,005 renal biopsies in 840 patients, mean age 37.7 +/- 13.1 years, 67% female. There were no complications in 88.8% (893 biopsies), minor complications in 8.65% (87 biopsies) and only in 2.4% of the procedures major complications. We divided the cases in two groups: percutaneous renal biopsy without complications (n = 893, 89%) and with complications (n = 112, 11%). The most frequent complications were hematuria (91 cases, 9.1%) and perirenal hematoma (29 cases, 2.7%). In these cases transfusion was required in 2.4% (26). Infectious complications were: urosepsis in 7 cases (0.7%), bacteremia, sepsis and perirenal abscesses (1 case each, 0.1%). One patient died because of multiple complications (0.1%). We observed greater risk of major complications on patients in those who biopsy was done because of acute renal failure (OR 4.03, p < 0.003). DISCUSSION: In our experience percutaneous renal biopsy is a low risk procedure. Most complications are minor and without clinical repercussion. There must be a strict selection criteria of the patients to whom percutaneous renal biopsy is going to be done because of the risk of severe complications.
Assuntos
Biópsia por Agulha/efeitos adversos , Rim/patologia , Abscesso/etiologia , Injúria Renal Aguda/diagnóstico , Injúria Renal Aguda/patologia , Adulto , Feminino , Hematoma/etiologia , Hematúria/etiologia , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Fatores de Risco , Infecções Urinárias/etiologiaRESUMO
INTRODUCTION: Continuous replacement therapy of renal function has gained acceptance over the last decade for the treatment of acute renal failure. In the present study we present our experience using continuous hemodialysis (CHD) in our institution. PATIENTS AND METHODS: This is a prospective analysis of the CHD treated patients in the intensive care unit (ICU) of our institution over an 24-month period. CHD was performed through a double-lumen catheter such as Mahurkar. We have performed 28 CHD procedures in 28 patients, from which four were excluded from the analysis. Three patients were excluded as CHD lasted less than 12 hours and one patient because he had chronic renal failure. The studied variables were: heart and respiratory rate, mean arterial pressure, body temperature, APACHE II classification status, arterial gasometry, cell blood count, BUN, creatinine, serum electrolytes, and hepatic enzymes. We also registered urine output, diuretic use, and the mean dose of inotropic drugs employed per day. These variables were obtained at the admittance to the ICU, before the initiation of CHD and after 24 and 48 hours. We also registered age, gender, and final evolution. RESULTS: We evaluated 24 patients with mean age of 58.1 +/- 17.5 years in which CHD was use for a mean time of 4.6 +/- 2.8 days. Total ultrafiltrate was 19.5 +/- 8.4 liters, for a mean of 4.2 liters per day. CHD resulted in improvement of heart and respiratory rate, mean arterial pressure and laboratory variables such as arterial pH, bicarbonate concentration, BUN and potassium. It also decreased significant by the use of inotropic drugs. Five out of twenty-four patients survived (20.8%). The survived patients had significant lower age than the died patients (39.2 +/- 20 years vs. 63 +/- 13.3; p < 0.001), lower time between the admittance to ICU and the beginning of CHD (1.4 +/- 0.5 days vs. 3.5 +/- 2.6; p < 0.01) and lower APACHE II classification at admittance to ICU (7.4 +/- 1.6 vs. 19.0 +/- 2.7; p < 0.001) and at the start of CHD (13.6 +/- 3.2 vs. 24.7 +/- 3.7; p < 0.001). However, multivariate analysis revealed that the only variable associated with a better survival was a lower time between the admittance to intensive care and the beginning of CHD. DISCUSSION: CHD is a safe technique that can be used for acute renal failure patients who have contraindications for intermittent HD. This technique can be used in hospitals offering intermittent hemodialysis and intensive care. CHD use is associated with improvement of hemodynamic and metabolic alterations in patients with shock. Our data support the concept that the earlier the initiation of CHD the better the prognosis.