Customisation and validation of a low-volume plasma renin activity immunoassay: Enabling of regulatory compliant determination in paediatric trials.

OBJECTIVES: Investigations of plasma renin activity (PRA) in children are urgently required. Small-volume, regulatory guideline compliant, bioanalytical assays tailored for paediatric application could facilitate to overcome this hurdle. Ethical constraints given e.g. by the European Medicines Agency need to be addressed and reliable data generation in line with Good Clinical Laboratory Practice must be ensured. METHODS: A PRA enzyme-linked immunosorbent assay (ELISA) was tailored for paediatric application and validated in the context of the U.S. Food and Drug Administration bioanalytical guideline. Performance verification of the assay was conducted by participation in an interlaboratory ring test, evaluation of incurred sample reanalysis and an application-orientated approach in children. RESULTS: A five-fold reduction of required plasma volume to 100 µL was achieved without limiting the calibration range. Between-run accuracy and precision varied no more than 5.0% and 6.3%, respectively. No substantial matrix effect was detected and the inter-run precision for parallelism was 11.1%. Stability experiments approved the freeze-thaw stability, short-term stability as well as 37 weeks of long-term stability. The assay successfully participated in the interlaboratory ring test, showing non-inferiority regarding radioimmunoassay (RIA). Moreover, PRA in plasma samples of neonates was successfully determined. Conducted incurred sample reanalysis confirmed the comparability and reliability of the assay with regard to international regulatory bioanalytical guidelines. CONCLUSION: A fit-for-purpose PRA ELISA characterised by low-volume application was successfully established, indicating non-inferiority regarding commonly applied RIAs. Reliability of the regulatory-compliant PRA assay was proven by participation in an interlaboratory ring test and its application in a paediatric population.

Levels of angiotensin peptides in healthy and cardiovascular/renal-diseased paediatric population-an investigative review.

The renin-angiotensin-aldosterone system (RAAS) plays a major role in the regulation of blood pressure and homeostasis. Therefore, it is a commonly used target for pharmacotherapy of cardiovascular diseases in adults. However, the efficacy of this pharmacotherapy can only be limitedly derived into children. Comprehensive knowledge of the humoral parameters acting in the paediatric RAAS (e.g. angiotensin I, angiotensin II, angiotensin 1-7, angiotensin III, and angiotensin IV) might facilitate a more effective and rational pharmacotherapy in children. Therefore, this review aims to provide an overview of the maturing RAAS. Out of 925 identified records, 35 publications were classified as relevant. Physiological and pathophysiological concentrations of angiotensin peptides were compiled and categorised according to European Medicines Agency age groups. Age has a major impact on circulating angiotensin I, angiotensin II, and angiotensin 1-7, which is reflected in an age-dependent decrease during childhood. In contrast to data obtained in adults, no gender-related differences in angiotensin levels were identified. The observed increase in peptide concentrations regarding cardiac- and renal-diseased children is influenced by surgical repair, while evidence for a pharmacological impact is conflicting. A comprehensive set of angiotensin I, angiotensin II, and angiotensin 1-7 values from neonates up to adolescents was compiled. Indicating age as a strong effector. However, evidence about potential promising targets of the RAAS like angiotensin III and angiotensin IV is still lacking in children.

Validated low-volume aldosterone immunoassay tailored to GCLP-compliant investigations in small sample volumes.

INTRODUCTION: Heart failure is well investigated in adults, but data in children is lacking. To overcome this shortage of reliable data, appropriate bioanalytical assays are required. OBJECTIVES: Development and validation of a bioanalytical assay for the determination of aldosterone concentrations in small sample volumes applicable to clinical studies under Good Clinical Laboratory Practice. METHODS: An immunoassay was developed based on a commercially available enzyme-linked immunosorbent assay and validated according to current bioanalytical guidelines of the EMA and FDA. RESULTS: The assay (range 31.3-1000 pg/mL [86.9-2775 pmol/L]) is characterized by a between-run accuracy from - 3.8% to - 0.8% and a between-run imprecision ranging from 4.9% to 8.9% (coefficient of variation). For within-run accuracy, the relative error was between - 11.1% and + 9.0%, while within-run imprecision ranged from 1.2% to 11.8% (CV). For parallelism and dilutional linearity, the relative error of back-calculated concentrations varied from - 14.1% to + 8.4% and from - 7.4% to + 10.5%, respectively. CONCLUSIONS: The immunoassay is compliant with the bioanalytical guidelines of the EMA and FDA and allows accurate and precise aldosterone determinations. As the assay can run low-volume samples, it is especially valuable for pediatric investigations.

Validated low-volume immunoassay for the reliable determination of direct renin especially valuable for pediatric investigations.

INTRODUCTION: The pharmacotherapy of pediatric patients suffering from heart failure is extrapolated from adults due to missing data in children. OBJECTIVES: Development and validation of a low-volume immunoassay for the reliable determination of renin. EXPERIMENTAL: The immunoassay was validated according to international guidelines. RESULTS: The assay allows the reliable determination of renin in 40 µL plasma within a calibration range of 4-128 pg/mL. Between-run accuracy varied from -3.3 to +3.0% (relative error), while between-run precision ranged from 4.9 to 11.3% (coefficient of variation). CONCLUSION: The low-volume immunoassay facilitates the reliable collection of pharmacodynamic data in children.

Synthetic dural graft septoplasty in epistaxis from hereditary hemorrhagic telangiectasia / Septoplastia con injerto de dura sintética en epistaxis por telangiectasias hemorrágicas hereditarias

Abstract It is an autosomal dominant vascular disorder, which has a variety of clinical manifestations, with epistaxis being one of the most common. Many treatment options exist for epistaxis, but with no consensus on which is the method of choice. We describe the case of a patient with hereditary hemorrhagic telangiectasia (HHT) secondary epistaxis with septoplasty managed with synthetic hard graft, which improved intensity and frequency of bleeding episodes. This technique is a variant of the septodermoplasty described by several authors, but the use of synthetic dura can help in obtaining better results and avoid taking skin grafts from other sites different from the surgical site.

Resumen Esta condición es un trastorno vascular autosómico dominante, que tiene una variedad de manifestaciones clínicas; entre las más comunes, se encuentra epistaxis. Existen múltiples opciones terapéuticas para la epistaxis, pero no hay un consenso sobre cuál es el método de elección. Se describe el caso de un paciente con epistaxis secundaria a telangiectasias hemorrágicas hereditarias (THH) manejado con septoplastia con injerto de dura sintética, la cual obtuvo mejoría en la intensidad y frecuencia de los episodios de sangrados. Esta técnica es un variante de la septodermoplastia descrita por diversos autores, pero el uso de dura sintética puede ayudar a obtener mejores resultados y evita toma de injertos dérmicos de otros sitios diferentes al sitio quirúrgico.

Synthetic dural graft septoplasty in epistaxis from hereditary hemorrhagic telangiectasia.

It is an autosomal dominant vascular disorder, which has a variety of clinical manifestations, with epistaxis being one of the most common. Many treatment options exist for epistaxis, but with no consensus on which is the method of choice. We describe the case of a patient with hereditary hemorrhagic telangiectasia (HHT) secondary epistaxis with septoplasty managed with synthetic hard graft, which improved intensity and frequency of bleeding episodes. This technique is a variant of the septodermoplasty described by several authors, but the use of synthetic dura can help in obtaining better results and avoid taking skin grafts from other sites different from the surgical site.

Esta condición es un trastorno vascular autosómico dominante, que tiene una variedad de manifestaciones clínicas; entre las más comunes, se encuentra epistaxis. Existen múltiples opciones terapéuticas para la epistaxis, pero no hay un consenso sobre cuál es el método de elección. Se describe el caso de un paciente con epistaxis secundaria a telangiectasias hemorrágicas hereditarias (THH) manejado con septoplastia con injerto de dura sintética, la cual obtuvo mejoría en la intensidad y frecuencia de los episodios de sangrados. Esta técnica es un variante de la septodermoplastia descrita por diversos autores, pero el uso de dura sintética puede ayudar a obtener mejores resultados y evita toma de injertos dérmicos de otros sitios diferentes al sitio quirúrgico.

Reparación endoscópica transnasal de la atresia de coanas. Estado del arte: resultados en 16 casos Hospital Universitario del Valle - Universidad del Valle. Cali, Colombia / Transnasal endoscopic repair of choanal atresia. State of the Art: results in 16 cases

Objetivo: Describir la epidemiologia local y la experiencia en el manejo de casos de atresia de coanas con la técnica de cirugía endoscópica transnasal e instrumental de poder. Diseño: Estudio retrospectivo. Metodología: Se toman 16 casos con diagnóstico de atresia de coanas, en los que fueron consideradas variables clínicas, método diagnóstico, lateralidad, tipo de atresia, manejo inicial y técnica quirúrgica. Se realizó análisis estadístico en Stata, versión 11.1. Resultados: En esta serie de casos, diez eran mujeres y seis hombres, con una relación mujer-hombre de 1,7:1; 56% de ellos fueron bilaterales, 56% de presentaron anomalías congénitas y la edad al diagnóstico fue postneonatal en el 81%. No se encontró asociación estadística entre sexo, tipo de atresia y lateralidad. El principal método diagnóstico fue la tomografía axial computarizada, en el 87,6% de los estudios. El 94% de los pacientes presentaron buen resultado quirúrgico funcional con la técnica endoscópica…

Objective: Describe the local epidemiology and the experience in the management of choanal atresia with endoscopic transnasal approach and power instruments. Methodology: Retrospective study of 16 cases with diagnosis of choanal atresia was considered variable clinics, diagnosis method, laterality, type of atresia, initial management and surgical technique. We performed statistical analysis in Stata, version 11.1. Results: In this series of cases, 10 was women and 6 was men, relation 1,7:1; 56% had associated congenital anomalies, the age of diagnosis was post neonatal 81%. There was no statistical association between sex, type of atresia and latelality. The main method diagnosis was the TAC in 87.6%. 94% of the patients showed a good surgical outcome with functional endoscopic technique. Conclusions: The experience observed in this series of cases with the use of technique endoscopic transnasal and power instrumentation (Shaver - Drill), represent a form of technique minimal invasive approach for this type of nasal congenital pathology with low degree of morbility, complications and excellent functional results…

Membrane translocation of glutaric acid and its derivatives.

The neurodegenerative disorder glutaric aciduria type I (GA I) is characterized by increased levels of cytotoxic metabolites such as glutaric acid (GA) and 3-hydroxyglutaric (3OHGA). The present report summarizes recent investigations providing insights into mechanisms of intra- and intercellular translocation of these metabolites. Initiated by microarray analyses in a mouse model of GA I, the sodium-dependent dicarboxylate cotransporter 3 (NaC3) was the first molecule identified to mediate the translocation of GA and 3OHGA with high and low affinity, respectively. More recently, organic anion transporters (OAT) 1 and 4 have been reported to be high-affinity transporters for GA and 3OHGA as well as D-2- and L-2-hydroxyglutaric acid (D2OHGA, L2OHGA). The concerted action of NaC3 and OATs may be important for the directed uptake and excretion of GA, 3OHGA, D2OHGA and L2OHGA in kidney proximal tubule cells. In addition, experimental data on cultured neuronal and glial cells isolated from mouse brain demonstrated that GA rather than 3OHGA may competitively inhibit the anaplerotic supply of tricarboxylic acid cycle intermediates from astrocytes to neurons. The identification of GA and GA derivative transporters may represent targets for new approaches to treat patients with GA I and related disorders.

[Therapy of viral hepatitis]. / Therapie der viralen Hepatitiden.

Chronic viral hepatitis is a leading cause of chronic hepatitis, liver cirrhosis, hepatic decompensation and hepatocellular carcinoma worldwide. Here, we will briefly review common indications and current therapies for chronic hepatitis B and C and discuss practical aspects of these therapies. Current therapies for hepatitis C aim at viral eradication. With the introduction of pegylated interferon and ribavirin viral eradication is successful in about 55% of treated patients. The goal of therapy of HBe antigen positive chronic hepatitis B is seroconversion to anti-HBe which can be achieved with interferon alpha in 25-45% of patients. A loss of HBs can be achieved in approximately 10%. Responders proceed significantly less to cirrhosis or hepatocellular carcinoma. Anti-HBe positive patients can be treated with interferon alpha or lamivudine. The former requires longer treatment and the results are disappointing. Lamivudine is a promising agent in the treatment of chronic hepatitis B, but the success is hampered by a high relapse rate and the emergence of viral resistance.

Transport of organic anions across the basolateral membrane of proximal tubule cells.

Renal proximal tubules secrete diverse organic anions (OA) including widely prescribed anionic drugs. Here, we review the molecular properties of cloned transporters involved in uptake of OA from blood into proximal tubule cells and provide extensive lists of substrates handled by these transport systems. Where tested, transporters have been immunolocalized to the basolateral cell membrane. The sulfate anion transporter 1 (sat-1) cloned from human, rat and mouse, transported oxalate and sulfate. Drugs found earlier to interact with sulfate transport in vivo have not yet been tested with sat-1. The Na(+)-dicarboxylate cotransporter 3 (NaDC-3) was cloned from human, rat, mouse and flounder, and transported three Na(+) with one divalent di- or tricarboxylate, such as citric acid cycle intermediates and the heavy metal chelator 2,3-dimercaptosuccinate (succimer). The organic anion transporter 1 (OAT1) cloned from several species was shown to exchange extracellular OA against intracellular alpha-ketoglutarate. OAT1 translocated, e.g., anti-inflammatory drugs, antiviral drugs, beta-lactam antibiotics, loop diuretics, ochratoxin A, and p-aminohippurate. Several OA, including probenecid, inhibited OAT1. Human, rat and mouse OAT2 transported selected anti-inflammatory and antiviral drugs, methotrexate, ochratoxin A, and, with high affinities, prostaglandins E(2) and F(2alpha). OAT3 cloned from human, rat and mouse showed a substrate specificity overlapping with that of OAT1. In addition, OAT3 interacted with sulfated steroid hormones such as estrone-3-sulfate. The driving forces for OAT2 and OAT3, the relative contributions of all OA transporters to, and the impact of transporter regulation by protein kinases on renal drug excretion in vivo must be determined in future experiments.

Anti-Fas induces hepatic chemokines and promotes inflammation by an NF-kappa B-independent, caspase-3-dependent pathway.

Agonistic antibodies against the Fas receptor, when administered to mice in vivo, cause significant apoptosis in the liver. In this study we show that anti-Fas antibody not only causes apoptosis of liver cells but also provokes hepatic inflammation. Two hours after injection of anti-Fas, when mice displayed evidence of caspase-3 activation and apoptosis, we found significant hepatic induction of the CXC chemokines macrophage inflammatory protein-2 and KC. Coincident with the chemokine induction was infiltration of the hepatic parenchyma by neutrophils. Neutralization experiments identified that chemokines were the cause of Fas-induced hepatic inflammation, with KC having the predominant effect. Chemokine induction in the livers of anti-Fas-treated mice was not associated with activation of NF-kappa B. Instead, it coincided with nuclear translocation of activator protein-1 (AP-1). AP-1 activation in liver was detected 1-2 h after anti-Fas treatment, suggesting a connection to the onset of apoptosis. When apoptosis was prevented by pretreating mice with a caspase-3 inhibitor, AP-1 activation and hepatic chemokine production were both significantly reduced. Hepatic inflammation was also reduced by 70%. Taken together, these findings indicate that Fas ligation can induce inflammation in the liver in vivo. Inflammation does not arise from Fas-mediated signaling through NF-kappa B; rather, it represents an indirect effect, requiring activation of caspase-3 and nuclear translocation of AP-1.

Virological and immunological effects of combination antiretroviral therapy with zidovudine, lamivudine, and indinavir during primary human immunodeficiency virus type 1 infection.

Forty-seven patients presenting with primary human immunodeficiency virus (HIV) infection were treated with zidovudine 200 mg 3 times a day, lamivudine 150 mg 2 times a day, and indinavir 800 mg 3 times a day for 1 year. From a mean pretreatment viral RNA level of 4.93 log(10) copies/mL, the proportions of patients having <500 copies/mL at 24 and 52 weeks were 92.0% and 89.2%, respectively. For the 35 patients with data available at 24 and 52 weeks, the corresponding proportions for the <50 copies/mL analysis were 86.6% and 79.3%, respectively. The change in virus load was -2.19 and -2.41 log(10) copies/mL at weeks 8 and 52, respectively. CD4 cell counts increased, from a mean of 546 cells/mm(3), by 142 cells/mm(3) at week 24 and by 210 cells/mm(3) at week 52. Three patients discontinued the study because of drug-related toxicity. Six (12.8%) patients had adverse experiences associated with nephrolithiasis. Combination therapy with zidovudine, lamivudine, and indinavir during primary HIV infection results in a profound and sustained reduction in virus load with concurrent recovery of the CD4 cell population.

Potential-dependent steady-state kinetics of a dicarboxylate transporter cloned from winter flounder kidney.

The two-electrode voltage-clamp technique in combination with tracer uptake experiments was used to investigate the dependence of dicarboxylate transport kinetics on membrane potential in Xenopus laevis oocytes expressing the flounder renal high-affinity-type sodium dicarboxylate cotransporter (fNaDC-3). Steady-state succinate-dependent currents in the presence of Na+ were saturable with an apparent affinity constant for succinate, K0.5,succ, of 60 microM. K0.5,succ was independent of membrane potential, suggesting succinate binding at the surface of the fNaDC-3 protein. The maximal succinate-dependent current, deltaImax, increased with hyperpolarization, suggesting that the empty carrier may translocate net charge. Succinate-induced currents showed sigmoidal dependence on Na+ concentration, and K0.5,Na+ decreased with hyperpolarization, suggesting Na+ binding in an ion well. Lowering the external Na+ concentration to 20 mM increased K0.5,succ approximately threefold. Succinate-induced currents were inhibited by Li+ with an Ki,Li+ of approximately 0.5 mM, and a Hill coefficient of below unity indicating the interaction of one Li+ ion with an inhibitory site at fNaDC-3.

Rare AIDS-defining diseases in the Swiss HIV Cohort Study.

The objective of this study was to investigate the spectrum and frequency of rare AIDS-defining diseases in the Swiss HIV Cohort Study. AIDS-defining diseases contributing less than 1% to the absolute number of all recorded AIDS-defining diseases in at least one of five periods (1988-1990, 1991-1992, 1993-1994, 1995-1996, 1997) were defined as being rare. A total of 9110 HIV-infected subjects were included in this study. Over the entire 9-year period, the following rare diseases were diagnosed: progressive multifocal leukoencephalopathy (n = 138), disseminated cryptococcosis (n = 67), visceral herpes simplex disease (n = 66), primary cerebral lymphoma (n = 65), indeterminate cerebral lesion (n = 50), cryptococcal meningitis (n = 34), Mycobacterium kansasii disease (n = 32), recurrent Salmonella septicemia (n = 22), intestinal isosporiasis (n = 21), candidiasis of the trachea, bronchi and lungs (n = 19), toxoplasma retinitis (n = 16), disseminated toxoplasmosis (n = 8), invasive cervical carcinoma (n = 8), extrapulmonary Pneumocystis disease (n = 5), disseminated histoplasmosis (n = 1) and disseminated coccidioidomycosis (n = 1). Rare diseases accounted for 7.3% of all AIDS-defining diseases over the entire 9-year period. Physicians should be aware of the likelihood of a broad spectrum of AIDS-defining diseases in HIV-infected patients.

Expression cloning and characterization of a novel sodium-dicarboxylate cotransporter from winter flounder kidney.

A cDNA coding for a Na+-dicarboxylate cotransporter, fNaDC-3, from winter flounder (Pseudopleuronectes americanus) kidney was isolated by functional expression in Xenopus laevis oocytes. The fNaDC-3 cDNA is 2384 nucleotides long and encodes a protein of 601 amino acids with a calculated molecular mass of 66.4 kDa. Secondary structure analysis predicts at least eight membrane-spanning domains. Transport of succinate by fNaDC-3 was sodium-dependent, could be inhibited by lithium, and evoked an inward current. The apparent affinity constant (Km) of fNaDC-3 for succinate of 30 microM resembles that of Na+-dicarboxylate transport in the basolateral membrane of mammalian renal proximal tubules. The substrates specific for the basolateral transporter, 2,3-dimethylsuccinate and cis-aconitate, not only inhibited succinate uptake but also evoked inward currents, proving that they are transported by fNaDC-3. Succinate transport via fNaDC-3 decreased by lowering pH, as did citrate transport, although much more moderately. These characteristics suggest that fNaDC-3 is a new type of Na+-dicarboxylate transporter that most likely corresponds to the Na+-dicarboxylate cotransporter in the basolateral membrane of mammalian renal proximal tubules.

NH4+ conductance in Xenopus laevis oocytes.II. Effect Of hypoosmolality.

Superfusing Xenopus laevis oocytes with NH4Cl (10 mmol/l, pH 7.5) resulted in an inward current at a clamp potential of -70 mV. In paired experiments (n=22), the NH4Cl-induced peak current was -293+/-94 nA, under control conditions (osmolality: 240 mosmol/kg), and rose to -523+/-196 nA when osmolality was reduced to 144 mosmol/kg. In parallel with the rise in NH4Cl-induced inward current, membrane conductance at -70 mV doubled and the zero-current potential changed from +3.3+/-9.4 mV to -22.0+/-8.0 mV (n=22) in the presence of NH4Cl during exposure to a hypoosmolar solution. In the absence of NH4Cl, oocytes responded to hypoosmolality with a shift in zero-current potential to more negative values and an increased conductance which became partially sensitive to isosorbiddinitrate (ISDN), suggesting the activation of a volume-sensitive K+ channel. Membrane conductance in the presence of NH4Cl was decreased by ISDN to similar extents under isoosmolal and hypoosmolal conditions, indicating that NH4+ enters the oocytes through a volume-sensitive conductance separate from the ISDN-sensitive K+ channel.

[Emergencies in HIV infection]. / Notfallsituationen bei HIV-Infektion.

Emergencies in HIV-infected patients are a common complication which may occur at any stage of the disease. Opportunistic infections may lead to irreversible damages of organs such as the brain, the eye or the lung. With the widely use of antiretroviral therapy side effects of reverse transcriptease inhibitors and proteinase inhibitors and drug interactions are frequent causes of severe symptoms such as nausea and diarrhoea or of complications such as anaemia or leucopenia. As with Non-HIV-associated emergencies empiric therapy may be necessary to treat patients to prevent severe organ damage.

Hydrolysis of dietary fat by pancreatic lipase stimulates cholecystokinin release.

BACKGROUND & AIMS: The hypothesis that cholecystokinin release requires adequate dietary fat digestion in the small intestine was investigated in 10 healthy volunteers, and the consequences of reduced fat hydrolysis on pancreaticobiliary secretions were assessed. METHODS: Fat hydrolysis was inhibited by intraduodenal perfusion of tetrahydrolipstatin, an irreversible lipase inhibitor. An oil emulsion containing 0, 30, 60, or 120 mg tetrahydrolipstatin was perfused. After a 40-minute basal period, a test meal was eaten to stimulate cholecystokinin release and pancreaticobiliary responses. RESULTS: In the control without tetrahydrolipstatin, lipase output increased threefold with meal ingestion and remained doubled for 4 hours. At the ligament of Treitz, free fatty acid concentration averaged 60% of total fatty acids. Increasing doses of tetrahydrolipstatin induced a dose-dependent inhibition of duodenal lipase activity (P < 0.01); 120 mg tetrahydrolipstatin eliminated the postprandial lipase peak activity, free fatty acid levels decreased to < 5% of total fatty acids, and plasma cholecystokinin levels were suppressed by 77% (P < 0.01). Amylase and trypsin outputs were reduced by 77% and 59%, respectively, and bilirubin secretion was virtually abolished (P < 0.01). CONCLUSIONS: These findings show that tetrahydrolipstatin prevents triglyceride hydrolysis and that plasma cholecystokinin release, gallbladder emptying, and pancreatic enzyme secretion require adequate triglyceride digestion. These data also support the concept of negative feedback regulation of cholecystokinin secretion.

NH4+ conductance in Xenopus laevis oocytes. I. Basic observations.

Current-clamp and voltage-clamp techniques were used to study the effects of NH4+ on the cell membrane conductance in Xenopus laevis oocytes. Superfusing the oocytes with NH4Cl resulted in a depolarization of the oocyte's cell membrane potential and, at a clamp potential of -70 mV, in an inward current. The magnitude of the inward current was proportional to the NH4Cl concentration in the extracellular solution and on membrane potential. The reversal potential, Erev , was -35.5 +/- 11.6 mV under control conditions and -3.1 +/- 11.0 mV (n = 19) in the presence of NH4Cl (10 mmol/l). Superfusion of the oocytes with nominally Ca2+-free solution affected the NH4Cl-evoked response only marginally. Replacement of extracellular Na+ by N-methyl-D-glucamine+ markedly reduced, but did not eliminate, the NH4Cl-sensitive current and shifted the reversal potential to more negative potentials. The NH4Cl-induced current was substantially inhibited by 0.1 mmol/l flufenamate, and was less affected by blockers of the endogenous K+ conductance, Ba2+ and isosorbiddinitrate (ISDN). The results are compatible with the activation of a conductance by NH4Cl for Na+ and NH4+. The mechanism by which NH4Cl activates the conductance remains unknown.