Famotidine,a histamine-2-receptor antagonist,inhibits the increase in rat gastric H+/K+-ATPase mRNA induced by intravenous infusion of gastrin 17 and histamine

We examined the effects of gastrin and histamine on rat gastric H⁺/K⁺-ATPase, the enzyme responsible for H⁺ secretion, gene expressionin vivo. Gastrin 17 (G 17) or histamine dihydrochloride (histamine) was continuously infused through the femoral vein of anesthetized rats. Gastric H⁺/K⁺-ATPase mRNA levels were measured using northern blot analysis. Infusion of G 17 and histamine increased the H⁺/K⁺-ATPase mRNA level significantly compared with basal control level or vehicle control level (P<0.01). However, pretreatment with famotidine, a potent histamine-2 (H₂)-receptor antagonist, inhibited the increase of rat gastric H⁺/K⁺-ATPase mRNA following G 17 and histamine infusion. These findings indicate that both histamine and G 17 increase expression of H⁺/K⁺-ATPase mRNA by activating H₂ receptor on the parietal cell.     

Effect of hypermethioninemia on some parameters of oxidative stress and on Na<Superscript>+</Superscript>,K<Superscript>+</Superscript>-ATPase activity in hippocampus of rats

In the present study we investigated the effect of chronic administration of methionine, a metabolite accumulated in many inherited pathological conditions such as methionine adenosyltransferase deficiency and homocystinuria, on some parameters of oxidative stress, namely thiobarbituric acid reactive substances (TBARS), catalase activity and total thiol content, as well as on Na⁺,K⁺-ATPase activity in rat hippocampus. For chronic treatment, rats received subcutaneous injections of methionine (1.34–2.68 μmol/g of body weight), twice a day, from the 6th to the 28th day of age and controls received saline. Animals were killed 12 h after the last injection. Results showed that chronic hypermethioninemia significantly increased TBARS, decreased Na⁺,K⁺-ATPase activity but did not alter catalase and total thiol content. Since chronic hypermethioninemia altered TBARS and Na⁺,K⁺-ATPase activity at 12 h after methionine administration, we also investigated the effect of acute administration of this amino acid on the same parameters studied after chronic methionine administration. For acute treatment,29-day-old rats received one single injection of methionine (2.68 μmol/g of body weight) or saline and were killed 1, 3 or 12 h later. Results showed that rats subjected to acute hypermethioninemia presented a reduction of Na⁺,K⁺-ATPase activity and an increase in TBARS when the animals were killed at 3 and 12 h, but not at 1 h, after methionine administration. These data indicate that hypermethioninemia increases lipid peroxidation which may, at least partially, explain the effect of methionine on the reduction in Na⁺,K⁺-ATPase activity. If confirmed in human beings, our findings could suggest that the induction of oxidative stress and the inhibition of Na⁺,K⁺-ATPase activity caused by methionine might contribute to the neurophysiopathology observed in patients with severe hypermethioninemia.     

Ammonia addedin vitro,but not moderate hyperammonemiain vivo,stimulates glutamate uptake and H+-ATPase activity in synaptic vesicles of the rat brain

The uptake of radiolabelled neurotransmitters: glutamate (GLU), GABA, and dopamine (DA) and the activity of the vacuolar type H⁺-pumping ATPase (H⁺-ATPase), were measured in crude synaptic vesicles treatedin vitro with a neurotoxic (3 mM) dose of NH₄ ⁺ (acetate or chloride), or isolated from rats with a moderate increase of brain ammonia (to 0.6 mM) induced by i.p. administration of ammonium acetate (HA rats) or a hepatotoxin-thioacetamide (HE rats).In vitro treatment with ammonium salts increased the sodium-independent, chloride-dependent uptake of GLU but did not stimulate the uptake of GABA or DA. Thein vitro treatment also stimulated the H⁺-ATPase activity. Since H⁺-ATPase generates the electrochemical gradient driving synaptic vesicular neurotransmitter transport, its stimulation by ammonia may have facilitated GLU uptake. However the GLU specificity of the effect must be related to other factors differentially affecting GLU uptake and the uptake of other neurotransmitters. Enhanced GLU accumulation in the synaptic vesicles may contribute to the increase of synaptic GLU exocytosis previously reported to accompany acute increases of brain ammonia to toxic levels. However, GLU uptake and H⁺-ATPase activity, but also the uptake of GABA and DA, were unchanged in synaptic vesicles prepared from rats with HA or HE. This indicates that changes in GLU and/or GABA release reported for moderate hyperammonemic conditions must be elicited by factors unrelated to the synaptic vesicular transport of the amino acids.     

Isoform-specific alterations in cardiac and erythrocyte Na ,K-ATPase activity induced by norepinephrine

Background: Myocardial Na⁺,K⁺-ATPase activities are decreased in congestive heart failure because of an increase in plasma norepinephrine levels, but it is difficult to monitor the activities in the clinical setting.Methods and Results: This study investigated whether erythrocyte Na⁺,K⁺-ATPase activity can reflect myocardial enzyme activity and whether isoform-specific alterations occur in the presence of catecholamine. Na⁺,K⁺-ATPase activity was measured by the colorimetric method by using the left ventricular myocardium and erythrocytes prepared from eight rabbits given norepinephrine for 7 days and from eight control rabbits that received saline. The protein levels of total catalytic subunit and α₁ - or α₃-isoform of Na⁺,K⁺-ATPase were determined by Western blot analysis. Na⁺,K⁺-ATPase activity was lower in both myocardium and erythrocytes from norepinephrine-treated rabbits than control rabbits (P < .01 and P < .01, respectively). There was a close correlation in Na⁺,K⁺-ATPase activity between myocardium and erythrocytes (r = .963). Total catalytic subunit protein level was lower in myocardium from norepinephrine-treated rabbits than control rabbits, but the α₁-isoform level was similar between the two groups. The α₃-isoform level was lower in norepinephrinetreated rabbits than control rabbits. In erythrocytes, α₁-isoform was lower in norepinephrinetreated rabbits than control rabbits.Conclusions: Na⁺,K⁺-ATPase activity in myocardium could be reflected in erythrocyte membrane, although there was a difference in isoform-specific regulation between the two.     

Nitric Oxide-Mediated Regulation of Gastric H+, K+-ATPase and Alcohol Dehydrogenase Following Ethanol-Induced Injury in Rats

The mucosal protective effect of nitric oxide(NO) was examined by usingN^G-nitro-L-arginine methyl ester (L-NAME) asnitric oxide synthase (NOS) inhibitor and nitroprusside(NP) as NO donating agent, in ethanol-induced rat gastric lesion model.The results are summarized as follows: (1) As gastrictissue samples were examined by light microscopy,intragastric exposure of ethanol was demonstrated to induce gastric injury, which was more prominentin female rats. The depletion of NO by L-NAME treatmentexacerbated the ethanol-induced gastric lesion but NPtogether with ethanol promoted repair of the mucosal injury, especially in female rats. (2)Gastric H⁺, K⁺-ATPase enzymeactivity, which was responsible for acid secretion,seemed not to be effected by ethanol treatment. Togetherwith ethanol, L-NAME treatment activated, whereas NP treatmentinhibited, the enzyme activity in female rats. (3)Ethanol treatment inhibited gastric alcoholdehydrogenase (ADH) activity, which was responsible forthe first-pass metabolism of ethanol. Together with ethanol,L-NAME did not effect the enzyme activity whereas NPtreatment disappeared the inhibitory effect of ethanolin both gender. Hydroxyl radical (OH) scavenger activity was found to increase in ethanol andethanol + NP groups in both sexes, but superoxideradical (O₂ ^-) scavengeractivity did not change. The results indicate that NOmay ameliorate the damaging effect of ethanol possibly by regulating acidsecretion, ethanol metabolism, and antioxidant contentin rat gastric mucosa.     

Effect of phenylalanine and p-chlorophenylalanine on Na+, K+-ATPase activity in the synaptic plasma membrane from the cerebral cortex of rats

Na⁺, K⁺-ATPase activity was measured in synaptic plasma membrane from cerebral cortex of Wistar rats subjected to experimental phenylketonuria, i.e., chemical hyperphenylalaninemia induced by subcutaneous administration of 5.2 μmol phenylalanine /g body weight (twice a day) plus 0.9 μmol p-chlorophenylalanine /g body weight (once a day). The treatment was performed from the 6^th to the 14^th postpartum day and rats were killed 12 h after the last injection. Synaptic plasma membrane from cerebral cortex was prepared by a discontinuous density sucrose gradient for Na⁺, K⁺-ATPase activity determination. The results showed that the enzyme activity was decreased by 30% in animals subjected to experimental phenylketonuria when compared to control. Thein vitro effects of the drugs on Na⁺, K⁺-ATPase activity were also investigated. Phenylalanine and p-chlorophenylalanine inhibited the enzyme activity and this inhibition was reversed by alanine. In addition, competition between phenylalanine and p-chlorophenylalanine for binding to the enzyme was observed, suggesting a common binding site for these substances. Our results suggest that reduction of Na⁺, K⁺-ATPase activity may be one of the mechanisms related to the brain dysfunction observed in human PKU.     

Intrastriatal Hypoxanthine Reduces Na<Superscript>+</Superscript>,K<Superscript>+</Superscript>-ATPase Activity and Induces Oxidative Stress in the Rats

The main objective of this study was to investigate the effects of a single intrastriatal injection of hypoxanthine, a metabolite accumulated in Lesch Nyhan disease and possibly involved in its neuropathology, on Na⁺,K⁺-ATPase activity, as well as on some parameters of oxidative stress, namely chemiluminescence (an index of lipid peroxidation), total radical-trapping antioxidant parameter—TRAP (an index of total antioxidant capacity of the tissue) and total thiol protein membrane content, in striatum, cerebral cortex and hippocampus of rats. Results show that hypoxanthine significantly decreased Na⁺,K⁺-ATPase activity and TRAP while increased chemiluminescence in all ipsislateral structures tested. However, no effect on total thiol protein membrane content was detected. We suggest that hypoxanthine induces oxidative stress in all cerebral structures studied (striatum, hippocampus and cerebral cortex) and that the reduction of Na⁺,K⁺-ATPase activity was probably mediated by reactive oxygen species.     

Quantification in crude homogenates of rat myocardial Na+, K+-and Ca2+-ATPase by K+ and Ca2+-dependent pNPPase. Age-dependent changes

Assays for complete quantification of Na⁺, K⁺-and Ca²⁺-ATPase in crude homogenates of rat ventricular myocardium by determination of K⁺-and Ca²⁺-dependentp-nitrophenyl phosphatase (pNPPase) activities were evaluated and optimized. Using these assays the total K⁺-and Ca²⁺-dependentpNPPase activities in ventricular myocardium of 11–12 week-old rats were found to be 2.98±0.10 and 0.29±0.02 mol×min^–1×g^–1 wet wt. (mean±SEM) (n=5), respectively. Coefficient of variance of interindividual determinations was 7 and 12%, respectively. The total Na⁺, K⁺-and Ca²⁺-ATPase concentrations were estimated to 2 and 10 nmol×g^–1 wet wt., respectively. Evaluation of a putative developmental variation revealed a biphasic age-related change in the rat myocardial Ca²⁺-dependentpNPPase activity with an increase from birth to around the third week of life followed by a decrease. By contrast, the K⁺-dependentpNPPase activity of the rat myocardium showed a decrease from birth to adulthood. It was excluded that the changes were simple out-come of variations in water and protein content of myocardium. Expressed per heart, the K⁺-and Ca²⁺-dependentpNPPase activity gradually increased to a plateau. The present assay for Na⁺, K⁺-ATPase quantification has the advantage over [³H] ouabain binding of being applicable on the ouabain-resistant rat myocardium, and is more simple and rapid than measurements of K⁺-dependent 3-0-methylfluorescein phosphatase (3-0-MFPase) in crude tissue homogenates. Furthermore, with few modifications thepNPPase assay allows quantification of Ca²⁺-ATPase on crude myocardial homogenates. Age-dependent changes in K⁺-and Ca²⁺-dependentpNPPase activities are of developmental interest and indicate the importance of close age match in studies of quantitative aspects of Na⁺, K⁺-and Ca²⁺-ATPase in excitable tissues.Abbreviations Na⁺, K⁺-ATPase sodium, potassium-dependent ATPase - Ca²⁺-ATPase caldium-dependent ATPase - pNP p-nitrophenyl - pNPP p-nitrophenyl phosphate - 3-0-MFP 3-0 methylfluorescein phosphate - DOC sodium deoxycholate     

Insulin does not regulate vascular smooth muscle Na+, K+-ATPase activity in rabbit aorta

Summary To determine whether insulin regulates vascular smooth muscle Na⁺, K⁺-ATPase activity and if impaired insulin stimulation of vascular smooth muscle Na⁺, K⁺-ATPase activity could be a cause of increased vascular reactivity to norepinephrine and angiotensin II in diabetic states, the effects of insulin on Na⁺, K⁺-ATPase activity were examined in normal rabbit aortic intima-media incubated with normal plasma glucose and myo-inositol levels for 30 min. Insulin at 100 U/ml (600 pmol/l) had no effect on Na⁺, K⁺-ATPase activity. At 250 U/ml it caused a 4.2±0.8% increase, and at 500 U/ml insulin caused a 17.7±1.4% increase in Na⁺, K⁺-ATPase activity that was completely inhibited by amiloride (1 mmol/l). Human insulin-like growth factor I (600 pmol/l) caused an 18.0±1.0% increase in Na⁺, K⁺-ATPase activity that was inhibited by amiloride. Insulin does not regulate (stimulate) aortic vascular smooth muscle Na⁺, K⁺-ATPase activity. Supraphysiological insulin concentrations, probably acting through an insulin-like growth factor I receptor, stimulate Na⁺/H⁺ exchange in aortic vascular smooth muscle and cause small secondary increases in Na⁺, K⁺-ATPase activity. In aortic intima-media incubated with normal plasma glucose and myo-inositol levels, endogenously released adenosine stimulates and maintains a component of resting Na⁺, K⁺-ATPase activity and stimulates acute increases in activity when norepinephrine (1 mol/l) or angiotensin II (100 nmol/l) is added. These adenosine-stimulated components of Na⁺, K⁺-ATPase activity are selectively inhibited when the medium glucose is raised to 30 mmol/l during a 30-min equilibration and 30-min incubation. Insulin (100 U/ml) added during the incubation had no effect on the alterations in Na⁺, K⁺-ATPase activity induced by glucose at an elevated plasma level. Impaired insulin stimulation of vascular smooth muscle Na⁺, K⁺-ATPase activity is not a possible cause for alterations in vascular reactivity in diabetes.     

Proline Administration Decreases Na+,K+-ATPase Activity in the Synaptic Plasma Membrane from Cerebral Cortex of Rats

Buffered proline was injected subcutaneously into rats twice a day at 8 h intervals from the 6^th to the 28^th day of age. Control rats received saline in the same volumes. The animals were weighed and killed by decapitation 12 h after the last injection. Cerebral cortex was used for the determination of Na⁺,K⁺-ATPase and Mg²⁺-ATPase activities. Body, whole brain and cortical weights were similar in the two groups. Na⁺,K⁺-ATPase activity was significantly reduced (by 20%) in membranes from the proline-treated group compared to the controls, whereas Mg²⁺-ATPase activity was not affected by proline. In another set of experiments, synaptic plasma membranes were prepared from cerebral cortex of 29-day-old rats and incubated with proline at final concentrations ranging from 0.1 to 2.0 mM. Na⁺,K⁺-ATPase activity, but not Mg²⁺-ATPase activity, was inhibited by 20-30%. Since proline concentrations in plasma of chronically treated rats and of type ll hyperprolinemic children are of the same order of magnitude as those tested in vitro, the results suggest that reduction of Na⁺,K⁺-ATPase activity may contribute to the neurological dysfunction found in some patients affected by type ll hyperprolinemia.     

Gastric H+, K+-ATPase as a therapeutic target in peptic ulcer disease

The presence of unbuffered acid appears to be an essential contributory factor in the pathogenesis of peptic ulcer disease. Treatment has concentrated therefore on the reduction of acidity, and the last decade has seen the widespread and effective use of H₂ antagonists. They are, at low doses, more successful in improving the natural history of duodenal ulcer disease than of gastric or esophageal ulceration. The H₂ receptor plays a central role in activation of parietal cell acid secretion, and antagonists at this receptor block most (but not all) of the acid secretion due to even gastrinergic or muscarinic (vagal) stimulation. In hypergastrinemic states such as Zollinger-Ellison syndrome, or where acid secretion has to be inhibited by more than 20% over a 24-hr period, such as for treatment of esophagitis, NSAID damage, or gastric ulcers, the dose and frequency of administration of the currently available antagonists must be increased to achieve reliable therapy. This has led to a search for an alternative target for acid inhibitory drugs, such as the gastric acid pump, the H⁺,K⁺-ATPase. This article focuses on the function of this ATPase and suggests that inhibition of this pump will provide a more efficacious means of reduction of acid secretion by the stomach, hence improving and simplifying therapy of acid related diseases.This work was supported in part by grants from NIH and the USVA.     

Cytosolic pH regulation in density-defined subpopulations of bronchoalveolar macrophages

Bronchoalveolar macrophages (m) represent a heterogeneous population of morphologically and functionally distinct cells. In mixed populations of bronchoalveolar m, cytosolic pH (pH _i ) regulation has been shown to involve both Na⁺-dependent and -independent mechanisms for H⁺ extrusion, i.e., passive H⁺ extrusion in exchange for extracellular Na⁺ (Na⁺-H⁺ exchange or NHE) and active H⁺ extrusion by plasmalemmal vacuolar-type H⁺-ATPase (V-ATPase), respectively. The present studies explored the possibility that individual subpopulations of bronchoalveolar m possess distinct ensembles of H⁺ extrusion mechanisms. Rabbit bronchoalveolar m were separated into five density-defined subpopulations using a discontinuous density gradient. Scanning and transmission electron microscopy revealed morphological differences between the subpopulations. The number of plasmalemmal projections and electron-dense inclusions increased with increments in cell density. The subpopulations were also functionally distinct. Fe receptor-mediated phagocytosis increased in the increasing density subpopulations. Despite these differences, all subpopulations displayed Na⁺-dependent and -independent mechanisms for pH _i recovery from intracellular acid loads (ammonia prepulse technique). We conclude that NHE and V-ATPase activities were present in each subpopulation. These findings support the use of mixed populations to study pH _i homeostasis in bronchoalveolar m. Offprint requests to: Akhil Bidani     

Changes in Antioxidant Status,Protein Concentration,Acetylcholinesterase, (Na<Superscript>+</Superscript>,K<Superscript>+</Superscript>)-, and Mg<Superscript>2+</Superscript>-ATPase Activities in the Brain of Hyper- and Hypothyroid Adult Rats

It is a common knowledge that metabolic reactions increase in hyperthyroidism and decrease in hypothyroidism. The aim of this work was to investigate how the metabolic reactions could affect the total antioxidant status (TAS), protein concentration (PC) and the activities of acetylcholinesterase (AChE), (Na⁺,K⁺)-ATPase and Mg²⁺-ATPase in the brain of hyper- and hypothyroid adult male rats. Hyperthyroidism was induced in rats by subcutaneous administration of thyroxine (25 g/100 g body weight) once daily for 14 days, while hypothyroidism was induced by oral administration of propylthiouracil (0.05%) for 21 days. TAS, PC, and enzyme activities were evaluated spectrophotometrically in the homogenated brain of each animal. TAS, PC, and Mg²⁺-ATPase activity were found unaffected in hyperthyroidism, while AChE and Na⁺,K⁺-ATPase activities were reduced by 25% (p < 0.01). In contrast, TAS, (Na⁺,K⁺)-ATPase and Mg²⁺-ATPase activities were found to be increased (approx. 23–30%, p < 0.001) in the hypothyroid brain, while AChE activity and PC were shown to be inhibited (approx. 23–30%, p < 0.001). These changes on brain enzyme activities may reflect the different metabolic effects of hyper- and hypothyroidism. Such changes of the enzyme activities may differentially modulate the brain intracellular Mg²⁺, neural excitability, as well as the uptake and release of biogenic amines.     

Inhibition of CO<Subscript>2</Subscript> production from glucose by arginine in brain slices of rats

In the present study we evaluated the in vivo effect of arginine on CO₂ production from glucose in a medium with physiological and high extracellular K⁺ concentrations. We also tested the influence of the nitric oxide synthase inhibitor, N^ω-nitro-L-arginine methyl ester (L-NAME), on the effects elicited by arginine in order to investigate the possible participation of NO and/or its derivatives on the effects of arginine on CO₂ production from glucose. Sixty-day-old rats were treated with a single intraperitoneal injection of saline (control; group I), arginine (0.8 g/kg; group II), L-NAME (2.0 mg/kg; group III) or arginine (0.8 g/kg) plus L-NAME (2.0 mg/kg; group IV) and were killed 1 h later. Results showed that arginine administration inhibited CO₂ production from glucose at physiological extracellular K⁺ concentration and L-NAME prevented such effect. In contrast, arginine administration had no effect on CO₂ production from glucose at high extracellular K⁺ concentration. Based on these data, we also investigated the in vitro effect of arginine on CO₂ production from glucose in a medium with physiological extracellular K⁺ concentration in hippocampus slices. Results showed that arginine (0.1–1.5 mM) when added to the incubation medium did not alter CO₂ production from glucose in hippocampus slices of untreated rats. In addition, we also demonstrated that arginine inhibits Na⁺, K⁺-ATPase activity. The data indicate that the reduction of CO₂ production by arginine was probably mediated by NO and/or its derivatives, which could act inhibiting the activity of Na⁺, K⁺-ATPase. The results suggest that arginine impairs energy metabolism in hippocampus slices of rats.     

Transgenic overexpression of translationally controlled tumor protein induces systemic hypertension via repression of Na+,K+-ATPase

Inhibition of Na⁺,K⁺-ATPase has been implicated in the pathogenesis of hypertension via its effect on smooth muscle reactivity and myocardial contractility. We recently demonstrated that translationally controlled tumor protein (TCTP) interacts with the 3rd cytoplasmic domain of Na⁺,K⁺-ATPase α₁-subunit and acts as its cytoplasmic repressor. Therefore, we hypothesized that repression of Na⁺,K⁺-ATPase by overexpressed TCTP might underlie the development of hypertension. In the present study, we confirmed that transgenic mice overexpressing TCTP developed systemic arterial hypertension at about 6 weeks after birth. Vascular smooth muscle of TCTP-overexpressing transgenic mice also displayed augmented contractile response to vasoconstrictors and attenuated relaxation response to vasodilators. These responses seem to be caused by reduced Na⁺,K⁺-ATPase activity and increased intracellular calcium, suggesting that inhibition of Na⁺,K⁺-ATPase by overexpression of TCTP is involved in the pathogenesis of hypertension. This study provides a new link between alteration of sodium pump activity and hypertension in vivo, and suggests that TCTP might be a therapeutic target for the treatment of hypertension.     

INTESTINAL DOPAMINERGIC ACTIVITY IN OBESE AND LEAN ZUCKER RATS: RESPONSE TO HIGH SALT INTAKE

The present study examined intestinal dopaminergic activity and its response to high salt (HS, 1% NaCl over a period of 24 hours) intake in obese (OZR) and lean Zucker rats (LZR). The basal Na⁺,K⁺-ATPase activity (nmol Pi/mg protein/min) in the jejunum of OZR was higher than in LZR on normal salt (NS) (OZR-NS=111.3±6.0 vs. LZR-NS=88.0±8.3). With the increase in salt intake, the basal Na⁺,K⁺-ATPase activity significantly increased in both animals (OZR-HS=145.9±11.8; LZR-HS=108.8±6.7). SKF 38393 (10?nM), a specific D₁-like dopamine receptor agonist, inhibited the jejunal Na⁺,K⁺-ATPase activity in OZR on HS intake, but failed to inhibit enzyme activity in OZR on NS intake and LZR on NS and HS intakes. The aromatic L-amino acid decarboxylase (AADC) activity in OZR was lower than in LZR on NS intake. The HS intake increased AADC activity in OZR, but not in LZR. During the NS intake the jejunal monoamine oxidase (MAO) activity in OZR was similar to that in LZR. The HS intake significantly decreased MAO activity in both OZR and LZR. The jejunal COMT activity in OZR was higher than in LZR on NS intake. The HS intake reduced COMT activity in OZR but not LZR. It is concluded that inhibition of jejunal Na⁺,K⁺-ATPase activity through D₁ dopamine receptors is dependent on salt intake in OZR, whereas in LZR, the enzyme failed to respond to the activation of D₁ dopamine receptors irrespective of their salt intake.     

Supplementation with vitamins E plus C or soy isoflavones in ovariectomized rats: effect on the activities of Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>-ATPase and cholinesterases

Since a previous study demonstrated that ovariectomized rats present an activation of Na⁺, K⁺-ATPase and acetylcholinesterase (AChE) activities, in the present study we investigated the influence of vitamins E plus C or soy isoflavones on the effects elicited by ovariectomy on the activities of these enzyme in hippocampus of ovariectomized rats. We also determined the effect of the same compounds on the reduction of serum butyrylcholinesterase (BuChE) activity caused by ovariectomy. Female adult Wistar rats were assigned to one of the following groups: sham (submitted to surgery without removal of the ovaries) and ovariectomized. Seven days after surgery, animals were treated for 30 days with a single daily intraperitoneous injection of vitamins E (40 mg/kg) plus C (100 mg/kg) or saline (control). In another set of experiments, the rats were fed for 30 days on a special diet with soy protein or a standard diet with casein (control). Rats were sacrificed after treatments and the hippocampus was dissected and serum was separated. Data demonstrate that vitamins E plus C reversed the activation of Na⁺, K⁺-ATPase and AChE in hippocampus of ovariectomized rats. Conversely, soy protein supplementation reversed the increase of AChE activity, but not of Na⁺, K⁺-ATPase activity, caused by ovariectomized group. Neither treatment was able to reverse the reduction of serum BuChE activity. Furthermore, treatments with vitamins E plus C or soy were unable to reverse the decrease in estradiol levels caused by ovariectomy. Our findings show that the treatment with vitamins E plus C significantly reversed the effect of ovariectomy on hippocampal Na⁺, K⁺-ATPase and AChE activities. However, a soy diet that was rich in isoflavones was able to reverse just the increase of AChE. Neither treatment altered the reduction in serum BuChE activity. Taken together, these vitamins and soy may have a protective role against the possible brain dysfunction observed in some menopause women. Vitamins E plus C and soy isoflavones may be a good alternative as a novel therapeutic strategy.     

Benign gastric polyps: morphological and functional origin

The most common types of benign gastric polyps are fundic gland polyps, hyperplastic polyps, and adenomas. The aim of this study was to determine on which morphological and functional background benign gastric polyps develop. The study includes 85 consecutive patients with gastric polyps and sex- and age-matched controls without polyps selected at random from a general population sample. The type of polyp was hyperplastic in 52 (61%), fundic gland in 18 (21%), adenoma in 10 (12%), carcinoid in 2 (2%), hamartoma in 2 (2%), and inflammatory fibroid in 1 (1%) of the cases. Routine biopsies from the gastric corpus and antrum were examined for presence of gastritis and H. pylori. Blood samples were analyzed for H. pylori antibodies, H⁺,K⁺-ATPase antibodies, gastrin, and pepsinogen I. Patients with hyperplastic polyps had increased P-gastrin concentrations and S-H⁺,K⁺-ATPase antibody titers and decreased S-pepsinogen I concentrations with a high prevalence of atrophic corpus gastritis or pangastritis. A similar pattern was observed among patients with adenomas, whereas patients with fundic gland polyps had normal serology and a lower prevalence of gastritis and H. pylori infection than controls. In conclusion, hyperplastic polyps and adenomas are generally associated with atrophic gastritis. Patients with fundic gland polyps seem to have a sounder mucosa than controls. Whereas the risk of malignant gastric neoplasia is increased in patients with hyperplastic polyps or adenomas, this does not seem to be the case in patients with fundic gland polyps.     

Synaptic Plasma Membrane Na<Superscript>+</Superscript>, K<Superscript>+</Superscript>-ATPase Activity is Significantly Reduced by the α-Keto Acids Accumulating in Maple Syrup Urine Disease in Rat Cerebral Cortex

The objective of the present study was to investigate the in vitro effects of the branched-chain α-keto acids accumulating in maple syrup urine disease, namely L-2-ketoisocaproic acid, L-2-keto-3-methylvaleric acid and L-2-ketoisovaleric acid on Na⁺, K⁺-ATPase activity in synaptic plasma membranes from cerebral cortex of 35-day-old rats. All keto acids significantly inhibited Na⁺, K⁺-ATPase activity at concentrations similar (1 mM) or even lower (0.5 mM) than those found in blood and cerebrospinal fluid of maple syrup urine disease patients. We also tested the effects of alanine on this enzyme activity. Alanine per se did not alter Na⁺, K⁺-ATPase activity, but totally prevented the branched-chain α-keto acids-induced Na⁺, K⁺-ATPase inhibition, indicating that alanine and the keto acids may possibly bind to the same site on the enzyme. We also observed that the branched-chain amino acids leucine, isoleucine and valine also inhibited Na⁺ K⁺-ATPase activity to a similar degree as that of the branched-chain α-keto acids and that alanine was able to fully prevent these effects. Considering that Na⁺, K⁺-ATPase is a critical enzyme for normal brain development and functioning, it is presumed that these findings may be involved in the pathophysiology of the neurological dysfunction of maple syrup urine disease.     

Angiotensin II AT1 Receptor/Signaling Mechanisms in The Biphasic Effect of The Peptide on Proximal Tubular Na+,K+-ATPase

The present study was designed to determine the cellular signaling mechanisms responsible for mediating the effects of angiotensin II on proximal tubular Na⁺,K⁺-ATPase activity. Angiotensin II produced a biphasic effect on Na⁺,K⁺-ATPase activity: stimulation at 10^-13-10^-10M followed by inhibition at 10^-7-10^-5M of angiotensin II. The stimulatory and inhibitory effects of angiotensin II were antagonized by losartan (1nM) suggesting the involvement of AT, receptor. Angiotensin IT produced inhibition of forskolin-stimulated CAMP accumulation at 10^-13-10^-10M followed by a stimulation in basal CAMP levels at 10^-7-10^-5M. Pretreatment of proximal tubules with losartan (1nM) antagonized both the stimulatory and inhibitory effects of angiotensin II on CAMP accumulation. Pretreatment of the proximal tubules with pertussis toxin (PTx) abolished the stimulation of Na⁺,K⁺-ATPase activity but did not affect the inhibition of Na⁺,K⁺-ATPase activity produced by angiotensin II. Pretreatment of the tubules with cholera toxin did not alter the biphasic effect of angiotensin II on Na⁺,K⁺-ATPase activity. Mepacrine (l0μM), a phospholipase A2 (PLA2) inhibitor, reduced only the inhibitory effect of angiotensin II on Na⁺,K⁺-ATPase activity. These results suggest that the activation of AT₁angiotensin II receptors stimulates Na⁺,K⁺-ATPase activity via a PTx-sensitive G protein-linked inhibition of adenylyl cyclase pathway, whereas the inhibition of Na⁺,K⁺-ATPase activity following AT₁receptor activation involves multiple signaling pathways which may include stimulation of adenylyl cyclase and PLA2