Improvement of Na+-K+ ATPase Activity and Gene Expression Associated with Glomerular Ultrastructural Protection in Diabetic Nephropathy by Acacia senegal: Role of Oxidative Stress Disturbances / Mejora de la actividad Na+-K+ ATPasa y la Expresión Génica Asociada con la Protección Ultraestructural Glomerular en la Nefropatía Diabética por Acacia senegal: Papel de las Alteraciones del Estrés Oxidativo

SUMMARY: This study assessed the effects of Acacia Senegal (AS) combined with insulin on Na+/K+-ATPase (NKA) activity and mRNA expression, serum glucose, renal function, and oxidative stress in a rat model of diabetic nephropathy (DN). Sixty rats were equally divided into six groups: normal control, normal+AS, diabetic (DM), DM+insulin, DM+AS, and DM+insulin+AS groups. Diabetes mellitus (type 1) was induced by a single injection of streptozotocin (65 mg/kg), and insulin and AS treatments were carried until rats were culled at the end of week 12. Serum glucose and creatinine levels, hemoglobin A1c (HbA1c) were measured. Renal homogenate levels of NKA activity and gene expression, malondialdehyde, superoxide dismutase (SOD), catalase and reduced glutathione (GSH) were evaluated as well as kidney tissue histology and ultrastructure. Diabetes caused glomerular damage and modulation of blood and tissue levels of creatinine, glucose, HbA1c, malondialdehyde, NKA activity and gene expression, SOD, catalase and GSH, which were significantly (p<0.05) treated with AS, insulin, and insulin plus AS. However, AS+insulin treatments were more effective. In conclusion, combined administration of AS with insulin to rats with DN decreased NKA activity and gene expression as well as oxidative stress, and improved glycemic state and renal structure and function.

Este estudio evaluó los efectos de Acacia senegal (AS) combinada con insulina sobre la actividad Na+/K+- ATPasa (NKA) y la expresión de ARNm, la glucosa sérica, la función renal y el estrés oxidativo en un modelo de nefropatía diabética (ND) en ratas. Sesenta ratas se dividieron equitativamente en seis grupos: control normal, normal+AS, diabética (DM), DM+insulina, DM+AS y DM+insulina+AS. La diabetes mellitus (tipo 1) se indujo mediante una única inyección de estreptozotocina (65 mg/kg), y los tratamientos con insulina y AS se llevaron a cabo hasta que las ratas fueron sacrificadas al final de la semana 12. Se midieron niveles séricos de glucosa y creatinina, hemoglobina A1c (HbA1c). Se evaluaron los niveles de homogeneizado renal de actividad NKA y expresión génica, malondialdehído, superóxido dismutasa (SOD), catalasa y glutatión reducido (GSH), así como la histología y ultraestructura del tejido renal. La diabetes causó daño glomerular y modulación de los niveles sanguíneos y tisulares de creatinina, glucosa, HbA1c, malondialdehído, actividad y expresión génica de NKA, SOD, catalasa y GSH, los cuales fueron tratados significativamente (p<0,05) con AS, insulina e insulina más AS. Sin embargo, los tratamientos con AS+insulina fueron más efectivos. En conclusión, la administración combinada de AS con insulina a ratas con DN disminuyó la actividad de NKA y la expresión genética, así como el estrés oxidativo, y mejoró el estado glucémico y la estructura y función renal.

The chemical profiling of aqueous soluble fraction from Lagopsis supina and its diuretic effects via suppression of AQP and RAAS pathways in saline-loaded rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Lagopsis supina (Steph.) Ik. -Gal. ex Knorr. has been widely used as a remedy treatment for diuresis and edema in China over 2500 years. Our previous results showed that the aqueous soluble fraction from L. supina (LSB) possessed acute diuretic effect. AIM OF THE STUDY: The aim of this study was to appraise the acute (6 h) and prolonged (7 d) diuretic effects, underlying mechanisms, and chemical profiling of LSB. MATERIALS AND METHODS: The chemical profiling of LSB was performed by ultra-high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-qTOF-MS/MS). Then, oral administration of LSB (40, 80, 160 and 320 mg/kg) and furosemide (10 mg/kg) once daily for 7 consecutive days to evaluate the diuretic effects in saline-loaded rats. The body weight, food consumption, and water intake were recorded once daily. The urinary volume, pH and electrolyte concentrations (Na+, K+, Cl-, and Ca2+) were measured after administration drugs for acute and prolonged diuretic effects. In addition, the serum levels of Na+-K+-ATPase, angiotensin II (Ang II), anti-diuretic hormone (ADH), aldosterone (ALD), atriopeptin (ANP), aquaporins (AQPs)-1, 2 and 3 were determined by ELISA kits. The mRNA expressions and protein levels of AQPs-1, 2 and 3 were analyzed by real-time quantitative PCR and Western blot assays, respectively. RESULTS: 30 compounds were identified in LSB based on accurate mass and MS/MS fragmentation compared to literature, among which phenylpropanoids and flavonoids could be partly responsible for the major diuretic effect. Daily administration of LSB (160 or 320 mg/kg) prominently increased urinary excretion volume after the 2 h at the first day of treatment, remaining until the 7th day. LSB did not cause Na+ and K+ electrolyte abnormalities, and has minor effect on Cl- and Ca2+ concentrations at 320 mg/kg. Furthermore, LSB observably suppressed renin-angiotensin-aldosterone system (RAAS) activation, including decreased serum levels of Ang II, ADH, and ALD, and prominently increased serum level of ANP in rats. LSB treatment significantly down-regulated the serum levels, mRNA expressions and protein levels of AQP1, AQP2, and AQP3. CONCLUSION: LSB has a prominent acute and prolonged diuretic effects via suppression of AQP and RAAS pathways in saline-loaded rats, and support the traditional folk use of this plant. Taken together, LSB might be a potential diuretic agent.

Monensin-Induced Increase in Intracellular Na+ Induces Changes in Na+ and Ca2+ Currents and Regulates Na+-K+ and Na+-Ca2+ Transport in Cardiomyocytes.

BACKGROUND/AIMS: Monensin, an Na ionophore, increases intracellular Na ([Na]i). Alteration of [Na]i influences ion transport through the sarcolemmal membrane. So far, the effects of monensin on ventricular myocytes have not been examined in detail. The main objective of this study was to elucidate the mechanism via which monensin-evoked increases in [Na]i affect the membrane potential and currents in ventricular myocytes of guinea pigs. METHODS: Membrane potentials and currents were measured using the whole-cell patch-clamp technique in single myocytes. The concentration of intracellular Ca ([Ca]i) was evaluated by measuring fluorescence intensity of Fluo-4. RESULTS: Monensin (10-5M) shortened the action potential duration (APD) and reduced the amplitude of the plateau phase. In addition, monensin decreased the sodium current (INa) and shifted the inactivation curve to the hyperpolarized direction. Moreover, it decreased the L-type calcium current (ICa). However, this effect was attenuated by increasing the buffering capacity of [Ca]i. The Na-Ca exchange current (INa-Ca) was activated particularly in the reverse mode. Na-K pump current (INa-K) was also activated. Notably, the inward rectifying K current (IK1) was not affected, and the change in the delayed outward K current (IK) was not evident. CONCLUSION: These results suggest that the monensin-induced shortened APD and reduced amplitude of the plateau phase are primarily due to the decrease in the ICa, the activation of the reverse mode of INa-Ca, and the increased INa-K, and second due to the decreased INa. The IK and the IK1 may not be associated with the abovementioned changes induced by monensin. The elevation of [Na]i can exert multiple influences on electrophysiological phenomena in cardiac myocytes.

Effect of free and nano-encapsulated curcumin on treatment and energetic metabolism of gerbils infected by Listeria monocytogenes.

Bacterial infections require special care since the indiscriminate use of antibiotics to treat them has been linked to the emergence of resistant strains. In this sense, phytoterapeutic alternatives such as curcumin and its nanocapsules have emerged as a promising supplement in optimizing availability of bioactives and reducing the development of antimicrobial resistance. Thus, the aim of this study was to verify the effects of pure and nanoencapsulated curcumin in the treatment of experimental listeriosis in gerbils regarding many aspects including antibacterial effect, antioxidant mechanisms involved and the energetic metabolism. Four groups were used containing 6 animals each: T0 (control), T1 (infected), T2 (infected and treated with free curcumin - dose of 30 mg/kg/day) and T3 (infected and treated with nanocapsules containing curcumin - a dose of 3 mg/kg/day). Treated animals received curcumin for 6 consecutive days starting 24 h after Listeria monocytogenes infection. All animals were euthanized on the 12th day after L. monocytogenes infection. Quantitative polymerase chain reaction (qPCR) identified L. monocytogenes DNA in the spleens of all animals of the T1 group, as well as T2 (2 out of 6) and T3 (5 out of 6). The weight of the spleens confirmed the infection, since it was larger in the T1 group, differing statistically from T0, and similarly to T2 and T3. Hepatic histopathological examination showed mild infiltration of neutrophils and macrophages, except for the T3 group (only 1/6). In the liver, the pyruvate kinase activity was higher in T1 and T2 compared to T0 and T3. The adenylate kinase activity did not differ between groups. The Na+/K+ATPase activity was lower in T1 group compared to T0 and T3. Lipoperoxidation was lower in the T3 group compared to groups T0, T1 and T2. The antioxidant capacity against peroxyl radicals was higher in T1, T2 and T3 groups compared to T0. In conclusion, free curcumin showed potent antibacterial effects; however, the nanoencapsulated form was able to minimize the effects caused by L. monocytogenes regarding tissue injury, changes on enzymes of the energetic metabolism, in addition to an antioxidant effect against lipoperoxidation.

[Enriching blood effect comparison in three kinds of blood deficiency model after oral administration of drug pair of Angelicae Sinensis Radix and Chuanxiong Rhizoma and each single herb].

OBJECTIVE: Through establishing different blood deficiency animal model, to evaluate enriching blood effect changes of the drug pair of Angelicae Sinensis Radix and Chuanxiong Rhizoma and each single herb, and to explore the effect characteristics of their compatibility. METHOD: Three different methods of acetyl phenylhydrazine (APH) hemolytic method, cyclophosphamide (CTX) chemical damage method, APH-CTX complex method were used respectively to copy different blood deficiency model mice. Changes of orbit blood routine, thymus index, spleen index and ATPase activity of red cell membrane of model mice were tested. RESULT: Compared with normal group, all indexes had significant differences in three model mice. The drug pair and each single herb had significant impact on most indexes of the APH-CTX complex model mice, and on the individual indexes of APH hemolytic model mice and CTX chemical damage model mice. Therefore, APH and CTX complex blood deficiency model was more suitable for the enriching blood mechanism study of the drug pair of Angelicae Sinensis Radix and Chuanxiong Rhizoma. Compared with the single herb of Angelicae Sinensis Radix and Chuanxiong Rhizoma, the drug pair of them had presented enriching blood effect at different extent with strengthening trend in regulating the invigorating blood indexes, immune organs and energy metabolic enzymes. CONCLUSION: The results of this research have provided scientific basis for revealing the mutual promotive composition law of the drug pair of Angelicae Sinensis Radix and Chuanxiong Rhizoma, and responded effectively the mult-link and mult-target effect characteristics of Chinese medicine bio-effect, to offer reference for the bio-effect research of the complicated substance group of Chinese medicine and traditional Chinese medicine formulae, and to supply demonstrative reference for researching the formulae compatibility law which takes the single drug-drug pair-formulae as main line.

In vitro effect of valepotriates isolated from Valeriana glechomifolia on rat P-type ATPases.

Valepotriates are iridoids found in variable amounts in Valerianaceae and might be among the bioactive compounds which confer anxiolytic properties to the Valeriana species. On the other hand, unspecific cytotoxicity has also been described. Presently, however, no particular molecular target has been defined for these compounds. Here we studied the effect of valtrate, acevaltrate, and 1- ß-acevaltrate isolated from Valeriana glechomifolia on the enzymatic activity of rat P-type ATPases. Valepotriates did not affect rat skeletal muscle sarco/endoplasmic reticulum Ca²âº-ATPase (SERCA) activity at the highest concentration used (100 µM). In contrast, the same concentration inhibited roughly half of the total H⁺/K⁺-ATPase activity from rat gastric epithelium (valtrate 54.6 ± 3.2 %, acevaltrate 60.7 ± 7.3 %, 1- ß-acevaltrate 50.2 ± 3.1 %; mean ± SEM, n = 3-5). Finally, these substances showed the highest inhibitory potency toward Na⁺/K⁺-ATPase, and the inhibition curves obtained provided a similar IC50 (in µM) for rat kidney α1 isoform (valtrate 21.2, acevaltrate 22.8, 1- ß-acevaltrate 24.4) and brain hemispheres α2/ α3 isoforms (valtrate 19.4, acevaltrate 42.3, 1- ß-acevaltrate 38.3). Our results suggest that P-type ATPases are differentially inhibited by valepotriates and that Na⁺/K⁺-ATPase might be one of their molecular targets in vivo.

Modulatory action of α-tocopherol on erythrocyte membrane adenosine triphosphatase against radiation damage in oral cancer.

To investigate the possible effects of α-tocopherol on erythrocyte membrane adenosine triphosphatases against radiation damage in oral cancer patients. Adenosine triphosphatase activities were analysed in oral cancer patients before and after radiotherapy (at a dosage of 6000 cGY in five fractions per week for a period of six weeks) and after supplemented with α-tocopherol (400 IU per day for entire period of radiotherapy). The membrane bound enzymes such as Na(+)/K(+)-ATPase, Ca(2+)-ATPase, Mg(2+)-ATPase and some trace elements were altered in oral cancer patients before and after radiotherapy. Supplemented with α-tocopherol modulates the erythrocyte membrane which is damaged by radiotherapy which suggests that α-tocopherol protects the erythrocyte membrane from radiation damage in oral cancer patients.

The two C-terminal tyrosines stabilize occluded Na/K pump conformations containing Na or K ions.

Interactions of the three transported Na ions with the Na/K pump remain incompletely understood. Na/K pump crystal structures show that the extended C terminus of the Na,K-adenosine triphosphatase (ATPase) alpha subunit directly contacts transmembrane helices. Deletion of the last five residues (KETYY in almost all Na/K pumps) markedly lowered the apparent affinity for Na activation of pump phosphorylation from ATP, a reflection of cytoplasmic Na affinity for forming the occluded E1P(Na3) conformation. ATPase assays further suggested that C-terminal truncations also interfere with low affinity Na interactions, which are attributable to extracellular effects. Because extracellular Na ions traverse part of the membrane's electric field to reach their binding sites in the Na/K pump, their movements generate currents that can be monitored with high resolution. We report here electrical measurements to examine how Na/K pump interactions with extracellular Na ions are influenced by C-terminal truncations. We deleted the last two (YY) or five (KESYY) residues in Xenopus laevis alpha1 Na/K pumps made ouabain resistant by either of two kinds of point mutations and measured their currents as 10-mM ouabain-sensitive currents in Xenopus oocytes after silencing endogenous Xenopus Na/K pumps with 1 microM ouabain. We found the low affinity inhibitory influence of extracellular Na on outward Na/K pump current at negative voltages to be impaired in all of the C-terminally truncated pumps. Correspondingly, voltage jump-induced transient charge movements that reflect pump interactions with extracellular Na ions were strongly shifted to more negative potentials; this signals a several-fold reduction of the apparent affinity for extracellular Na in the truncated pumps. Parallel lowering of Na affinity on both sides of the membrane argues that the C-terminal contacts provide important stabilization of the occluded E1P(Na3) conformation, regardless of the route of Na ion entry into the binding pocket. Gating measurements of palytoxin-opened Na/K pump channels additionally imply that the C-terminal contacts also help stabilize pump conformations with occluded K ions.

Neurochemical evidence that glycine induces bioenergetical dysfunction.

Glycine tissue concentrations are increased particularly in nonketotic and ketotic hyperglycinemia, inherited metabolic disorders characterized by severe neurologic damage and brain abnormalities. The present work investigated the in vitro effects of glycine on important parameters of energy metabolism in the brain of young rats. The parameters analyzed were CO2 generated from glucose, acetate and citrate and the activities of the respiratory chain complexes I-IV, of the citric acid cycle enzymes citrate synthase, aconitase, isocitrate dehydrogenase, alpha-ketoglutarate dehydrogenase, succinate dehydrogenase, fumarase and malate dehydrogenase, of creatine kinase and Na+,K+-ATPase. Our results show that glycine significantly reduced CO2 production from acetate, but not from glucose and citrate, reflecting an impairment of the citric acid cycle function. We also observed that the activity of the mitochondrial enzyme citrate synthase was markedly inhibited by glycine, whereas the other activities of the citric acid cycle were not altered. Furthermore, the activity of the respiratory chain was reduced at complexes I-III, II-III and II, as well as of the mitochondrial isoform of creatine kinase and Na+,K+-ATPase. The data indicate that glycine severely impairs brain bioenergetics at the level of energy formation, transfer and utilization. Considering the importance of energy metabolism for brain development and functioning, it is presumed that glycine-induced impairment of brain energy homeostasis may be involved at least in part in the neurological damage found in patients affected by disorders in which brain glycine concentrations are increased.

Vasoconstrictor and inotropic effects induced by the root bark extracts of Anthocleista schweinfurthii.

The present study was undertaken to investigate the cardiovascular effect of three extracts from the root bark of Anthocleista schweinfurthii Gilg.: an aqueous extract (AE), a dichloromethane extract (DCMR) and a fraction enriched in cardiac glycoside type compounds (CARDAN). In isolated perfused frog heart, bolus injection of the extracts produced a positive inotropic effect. The responses to AE and DCMR, but not to CARDAN, were depressed by propranolol. In isolated rat aorta, DCMR produced a transient increase in contractile tension while AE and CARDAN induced a sustained constriction. AE vasoconstrictor effect was abolished by phentolamine, while contraction evoked by CARDAN was antagonized by verapamil. In aortic rings contracted in low K+ media, the addition of K+ evoked a relaxation, which was abolished by ouabain, depressed by DCMR but not affected by either A(E) or CARDAN. These observations indicate that Anthocleista schweinfurthii contains substances that promote vasoconstriction and increase cardiac contraction. The effect of DCMR was only partially mediated by inhibition of the Na+ pump while the mechanism of action of A(E) and CARDAN was distinct from the inhibition of the Na+, K+ - ATPase pump, but could involve adrenergic receptors, or either direct or indirect activation of L-type calcium channels.

[Effects of methyl protodioscin on [Ca2+]i and ATPase activity in cardiomyocytes and analysis of mechanisms].

OBJECTIVE: To study the effects of methyl protodioscin on the [Ca2+]i and the ATPase activity in cardiomyocytes, as well as their mechanisms. METHOD: The cardiomyocytes were randomly divided into three groups, the control group treated with no serumal DMEM, the MPD group treated with MPD and the dilthiazem group treated with dilthiazem. Fluorospectrophotometer was used to determined the level of myocardial cell intracellular Ca2+ [Ca2+]i. In the experiment of ATPase activity on cellular membrane, the cardiomyocytes were randomly divided into two groups, the control group treated with no serumal DMEM, the MPD group treated with MPD. The activity of Na+-K+-ATPase,Ca2+-Mg2+-ATPase and Mg2+-ATP ATPase were determined. The quantitative analysis of SERCA2a mRNA expression was studied by RT-PCR that the groups and treatments in cardiomyocytes same as the experiment for ATPase activity assay. RESULT: Under the quiescent condition, compared to the control group, the level of [Ca2+]i in cardiomyocytes of the MPD group and dilthiazem group was no different. After treatment with 40 mmol x L(-1) KCl, [Ca2+] was significantly lower in the MPD group and the dilthiazem group, and the intensity of peak value in time course of 60 s, the dilthiazem group and the MPD group also were lower than the control group (P < 0.001). Ca2+-Mg2+-ATPase and Na+-K+-ATPase in cultured rat were increased after treated with MPD compared to treatment with no serumal DMEM (P < 0.05, P < 0.01), but Mg2+-ATPase in these groups had no different. The expression of SERCA2a mRNA between the MPD group and the control group was no different. MPD could not up-regulated or down-regulated SERCA2a in endocytoplasmic reticulum. CONCLUSION: Methyl protodioscin could block the volt dependent form calcium channel in cellular membrane, and up-regulate the function of sodium pump and calcium pump, so that it could remain low calcium in the internal environment in cardiomyocytes.

Response of sodium pump to ouabain challenge in human glioblastoma cells in culture.

Bipolar disorder is a severe psychiatric condition that manifests with abnormalities in ion regulation. Previous studies have suggested that glia may be specifically involved in the pathophysiology of this condition. Since the potent sodium pump inhibitor, ouabain, has been used previously to model the ionic changes of bipolar illness, we investigated its effect of on sodium pump expression and activity in a human glioblastoma cell line. LN229 cells were grown with or without ouabain 10(-7) M for 3 days, and the effect of a therapeutic concentration of lithium was also examined. The mRNA transcription of sodium pump isoforms was determined by reverse transcriptase polymerase chain reaction (RT-PCR), and the protein expression of phosphorylated and non-phosphorylated pump isoforms was semi-quantified utilizing Western blot. Ouabain treatment caused an increase of some 6-fold in alpha1 protein expression and a doubling of alpha1 mRNA. alpha3 protein and alpha2 and alpha3 mRNA more than doubled. Lithium treatment alone had no effect, but lithium co-administered with ouabain normalized Na pump protein and mRNA expression for alpha1 and 2, but not alpha3. These results suggest that disturbance of ion regulation induces changes in glial cell sodium regulatory systems which are normalized by lithium treatment.

Suppression of Na+/H+ exchanger isoform-3 in human inflammatory bowel disease: lack of reversal by 5'-aminosalicylate treatment.

OBJECTIVE: Na+/H+ exchanger isoform 3 (NHE-3) is responsible for net uptake of NaCl and water from the gastrointestinal (GI) tract. However, its status in human inflammatory bowel diseases (IBDs) such as ulcerative colitis(UC) and Crohn's disease (CD) remains poorly understood. The aim of this study was to investigate the underlying mechanism of NHE-3 isoform expression and its modulation by 5'-aminosalicylate in human CD and UC. MATERIAL AND METHODS: Subjects were divided into three groups: 1) controls; 2) untreated/new IBD cases (n = 13) and 3) 5'-aminosalicylate-treated IBD patients (n = 13). Subjects presenting with abdominal pain but with endoscopically normal colons served as normal controls. Inflammation was confirmed by the level of myeloperoxidase (MPO) activity, malondialdehyde (MDA) concentrations and by histologic evaluation. Expressions of NHE-3 protein and mRNA, sodium pump activity and IL-1beta and TNF-alpha mRNA were estimated in the colonic biopsies using ECL-Western blot analysis,reverse transcription-polymerase chain reaction (RT-PCR) and enzyme assays. RESULTS: The level of NHE-3 protein and sodium pump activity was reduced (p < 0.05) in both the untreated and treated CD and UC patients. NHE-3 mRNA was reduced only in CD patients but not in those with UC. The treatment reversed the symptoms, but levels of MPO activity, MDA concentration, IL-1beta, TNF-alpha and infiltration of inflammatory cells remained high with the exception of IL-1beta mRNA in the treated patients. CONCLUSIONS: NHE-3 suppression is regulated differentially in CD and UC, which together with suppression of sodium pump activity will reduce NaCl and water uptake from the colonic lumen. These findings suggest a role of TNF-a in the regulation of NHE-3 expression in IBD.

The toxicity of aconitine, emodin on ICC cell and the antagonist effect of the compatibility.

The study was to investigate the effect and action mechanism of aconitine and emodin on the function of the interstitial cells of Cajal (ICC) cultured in vitro. ICC cells were treated with aconitine (0.05-8%) and emodin (0.001-2%) in single or combined synchronous experiments and the effect of emodin on aconitine was evaluated using cell viability as end-point. Both the two compounds had toxicity on ICC cell. The cell membrane integrity impairment caused by the exposure lead to the efflux of intracellular ionic ([Na+], [Ca2+] and [K+]) and the deactivation of the Na+-K+-ATPase. The ionic disturbance caused the interruption of the cellular breathing chain and resulted in anaerobic metabolism increase and the glycogen massive decomposition, at last the energy metabolism in the cells was obstructed. But the antagonist effect existed when the two compounds were exposed to ICC cells together. The compatibility (aonitine:emodin as 2:1), can significantly reversed the toxicity of aconition. In addition, synergistic effects were never observed in the range of concentrations considered. Although emodin can defer the aconition's toxicity on ICC cell, the impairment can't be totally inhibited by the compatibility with time went on. The results of our work represent a starting point to generate novel information on the interactions between aconitine and emodin in vitro, as well as a new relevant experimental approach useful to investigate the Herb compatibility with aconite and rhubarb and reference for the clinic.

Effect of clotrimazole on the pump cycle of the Na,K-ATPase.

The effect of the antimycotic drug clotrimazole (CLT) on the Na,K-ATPase was investigated using fluorescence and electrical measurements. The results obtained by steady-state fluorescence experiments with the electrochromic styryl dye RH421 were combined with those achieved by a pre-steady-state method based on fast solution exchange on a solid supported membrane that adsorbs the protein. Both techniques are suitable for monitoring the electrogenic steps of the pump cycle and are in general complementary, yielding distinct kinetic information. The experiments show clearly that CLT affects specific partial reactions of the pump cycle of the Na,K-ATPase with an affinity in the low micromolar range and in a reversible manner. All results can be consistently explained by proposing the CLT-promoted formation of an ion-occluded-CLT-bound conformational E(2) state, E(2)(CLT)(X(2)) that acts as a "dead-end" side track of the pump cycle, where X stands for H+ or K+. Na+ binding, enzyme phosphorylation, and Na+ transport were not affected by CLT, and at high CLT concentrations approximately (1/3) of the enzyme remained active in the physiological transport mode. The presence of Na+ and K+ destabilized the inactivated form of the Na,K-ATPase.

Biochemical effects of pretreatment with vitamins E and C in rats submitted to intrastriatal hypoxanthine administration.

We previously demonstrated that intrastriatal injection of hypoxanthine, the major metabolite accumulating in Lesch-Nyhan disease, inhibited Na+,K+-ATPase activity and induced oxidative stress in rat striatum. In the present study, we evaluated the action of vitamins E and C on the biochemical alteration induced by hypoxanthine administration on Na+,K+-ATPase, TBARS, TRAP, as well as on superoxide dismutase (SOD), catalase (CAT) and glutathione-peroxidase (GPx) activities in striatum of adult rats. Animals received pretreatment with vitamins E and C or saline during 7 days. Twelve hours after the last injection of vitamins or saline, animals were divided into two groups: (1) vehicle-injected group and (2) hypoxanthine-injected group. For all parameters investigated in this research, animals were sacrificed 30 min after drug infusion. Results showed that pretreatment with vitamins E and C prevented hypoxanthine-mediated effects on Na+,K+-ATPase, TBARS and antioxidant enzymes (SOD, CAT and GPx) activities; however the reduction on TRAP was not prevented by these vitamins. Although extrapolation of findings from animal experiments to humans is difficult, it is conceivable that these vitamins might serve as an adjuvant therapy in order to avoid progression of striatal damage in patients affected by Lesch-Nyhan disease.

Neurotoxicological effects of cinnabar (a Chinese mineral medicine, HgS) in mice.

Cinnabar, a naturally occurring mercuric sulfide (HgS), has long been used in combination with traditional Chinese medicine as a sedative for more than 2000 years. Up to date, its pharmacological and toxicological effects are still unclear, especially in clinical low-dose and long-term use. In this study, we attempted to elucidate the effects of cinnabar on the time course of changes in locomotor activities, pentobarbital-induced sleeping time, motor equilibrium performance and neurobiochemical activities in mice during 3- to 11-week administration at a clinical dose of 10 mg/kg/day. The results showed that cinnabar was significantly absorbed by gastrointestinal (G-I) tract and transported to brain tissues. The spontaneous locomotor activities of male mice but not female mice were preferentially suppressed. Moreover, frequencies of jump and stereotype-1 episodes were progressively decreased after 3-week oral administration in male and female mice. Pentobarbital-induced sleeping time was prolonged and the retention time on a rotating rod (60 rpm) was reduced after treatment with cinnabar for 6 weeks and then progressively to a greater extent until the 11-week experiment. In addition, the biochemical changes in blood and brain tissues were studied; the inhibition of Na(+)/K(+)-ATPase activities, increased production of lipid peroxidation (LPO) and nitric oxide (NO) were found with a greater extent in male mice than those in female mice, which were apparently correlated with their differences in the neurological responses observed. In conclusion, these findings, for the first time, provide evidence of the pharmacological and toxicological basis for understanding the sedative and neurotoxic effects of cinnabar used as a Chinese mineral medicine for more than 2000 years.

Erythrocyte membrane Na+,K+-ATPase and Mg2+-ATPase activities in subjects with methylenetetrahydrofolate reductase (MTHFR) 677 C-->T genotype and moderate hyperhomocysteinaemia. The role of L-phenylalanine and L-alanine.

BACKGROUND: Increased homocysteine (Hcy) blood levels are correlated with vascular and neurological problems. The aim of our study was to investigate erythrocyte membrane Na(+),K(+)-ATPase and Mg(2+)-ATPase activities in patients with methylenetetrahydrofolate reductase (MTHFR) 677 C-->T genotype. METHODS: Blood was obtained from 25 patients before and after folic acid supplementation and from controls (n=30) once. Plasma folate, vitamin B(12) and total antioxidant status (TAS) were measured using commercial kits, Hcy was determined by HPLC and membrane enzyme activities were measured spectrophotometrically. RESULTS: Mg(2+)-ATPase remained unaltered. Membrane Na(+),K(+)-ATPase activity was remarkably increased in patients (0.77+/-0.06 micromol Pi/h x mg protein) and decreased to normal levels (0.52+/-0.05 micromol Pi/h x mg protein; p<0.001) after therapy. TAS did not differ significantly before and after treatment. Hcy levels were significantly higher before therapy (25.4+/-2.8 micromol/L) than levels after therapy (12.1+/-2.0 micromol/L; p<0.001) and in controls (10.5+/-2.5 micromol/L, p<0.001). In vitro, L-phenylalanine (Phe) reversed to normal the stimulated enzyme from patients before therapy. In addition, Phe incubation of the Hcy activated membrane Na(+),K(+)-ATPase from controls resulted in restoration of its activity, whereas L-alanine (Ala) incubation protected the enzyme from Hcy activation. CONCLUSIONS: The increased membrane Na(+),K(+)-ATPase activity may be due to high -SH group Hcy levels. In vitro, Phe reversed the increase in enzyme activity induced by Hcy in controls, as well as the stimulated membrane enzyme in untreated patients. Ala protected the enzyme from Hcy action.

Copper modifies the activity of sodium-transporting systems in erythrocyte membrane in patients with essential hypertension.

The aim of the study was to verify the hypothesis if copper could influence the activity of sodium-transporting systems in erythrocyte membrane that could be related to essential hypertension. The examined group of patients consisted of 15 men with hypertension. The control group was 11 healthy male volunteers. The Na+/H+ exchanger (NHE) activity in erythrocytes was determined according to Orlov et al. The activity of transporting systems (ATP-Na+/K+; co-Na+/K+/Cl-; ex-Na+/Li+; free Na+ and K+ outflow [Na+, K+-outflow]) was determined according to Garay's method. The concentration of copper in plasma was assessed using atomic absorption spectrometry. The activity of ATP-Na+/K+ (micromol/L red blood cells [RBCs]/h) in hypertensive patients was 2231.5 +/- 657.6 vs 1750.5 +/- 291 in the control (p < 0.05), the activity of co-Na+/K+/Cl- (micromol/L RBCs/h) in hypertensives was 171.3 +/- 77.9 vs 150.7 +/- 53.9 in the control (NS). Na+-outflow (micromol/L RBCs/h) in hypertensives was 118.3 +/- 51.6 vs 113.3 +/- 24.4 in the control (NS). The K+-outflow (micromol/L RBCs/h) in hypertensives was 1361.7 +/- 545.4 vs 1035.6 +/- 188.3 in the control (NS). The activity of ex-Na+/Li+ (micromol/L RBCs/h) in hypertensive patients was 266.1 +/- 76.1 vs 204.1 +/- 71.6 in the control (p < 0.05). NHE activity (mmol/L RBCs/h) in hypertensives was 9.7 +/- 2.96 vs 7.7 +/- 1.33 in the control (p < 0.05). In hypertensive patients, negative correlation was found between the activity of Na+/K+/Cl- co-transport and plasma copper concentration (Rs = -0.579, p < 0.05) and between the activity of ex-Na+/Li+ and plasma copper concentration (Rs = -0.508, p < 0.05). Plasma copper concentration significantly influences the activity of sodium transporting systems in erythrocyte membrane. Copper supplementation could be expected to provide therapeutic benefits for hypertensive patients.

A new steroidal saponin from AGAVE brittoniana and its biphasic effect on the Na+-ATPase activity.

A new steroidal saponin, 3-{(O-6-deoxy-a-L-mannopyranosyl-(1 --> 4)-O-beta-D-glucopyranosyl-(1 --> 3)-O-[O-beta-D-glucopyranosyl-(1 --> 3)-beta-D-glucopyranosyl-(1 --> 2)]-O-beta-D-glucopyranosyl-(1 --> 4)-beta-D-galactopyranosyl)oxy}-6-hydroxy-(3beta,5alpha,6alpha,25R)-spirostan-12-one, was isolated from Agave brittoniana Trel. The structure was determined by extensive NMR spectroscopy studies and chemical conversions. Its effects on the Na+-ATPase and (Na+ + K+)-ATPase activities of the proximal tubule from pig kidney were evaluated. It was observed that this steroidal saponin exerts a biphasic effect on the Na+-ATPase activity. It is concluded that the effect of the aqueous extract as a diuretic is due, at least in part, to the action of saponin on the ouabain-insensitive Na+-ATPase.