Moxonidine inhibits Na+/H+ exchange in proximal tubule cells and cortical collecting duct

The lateral arm free flap can be harvested as a fascial flap or fasciocutaneous flap. In this report we describe the use of the lateral arm fascial flap for degloving injuries of the fingers and for skin loss on the dorsum of the hand with exposure of tendons and bones. Concomitant reconstruction of a missing phalanx with a portion of the distal humerus is also described. The use of the fascial flap allows a large area of tissue to be harvested, and still, the donor site can be closed primarily. The fascia is thin and pliable and so conforms well to the contour of the fingers. Its bulk does not interfere with finger motion, and its undersurface creates a gliding surface for tendons. Complications in the reported cases were negligible.     

Intracellular pH regulation in bovine aortic endothelial cells: evidence of both Na+/H+ exchange and Na+-dependent Cl-/HCO3- exchange

Regulation of intracellular pH (pHi) was studied in cultured bovine aortic endothelial cells, an important cell system for cardiovascular research. Suspended cells were acidified by the NH4Cl prepulse technique as well as by exposure to CO2/HCO3-. Subsequent rates of pHi recovery were monitored using the fluorescent dye 2',7'-bis(2-carboxyethyl)-5-(6)-carboxyfluorescein (BCECF). In HCO3(-)-free solutions, an EIPA-sensitive, Na+-dependent mechanism fully accounted for realkalinization, namely the Na+/H+ exchanger (NHE). In the presence of HCO3-, an additional acid efflux mechanism was found. This one was dependent on Na+ and intracellular Cl-, EIPA-insensitive but DIDS-sensitive, and therefore represented a Na+-dependent Cl-/HCO3- exchanger (NCBE). In summary, two acid-extruding mechanisms were identified in bovine aortic endothelial cells: NHE and NCBE.     

Phenotype resembling Gitelman's syndrome in mice lacking the apical Na+-Cl- cotransporter of the distal convoluted tubule

Mutations in the gene encoding the thiazide-sensitive Na+-Cl- cotransporter (NCC) of the distal convoluted tubule cause Gitelman's syndrome, an inherited hypokalemic alkalosis with hypomagnesemia and hypocalciuria. These metabolic abnormalities are secondary to the deficit in NaCl reabsorption, but the underlying mechanisms are unclear. To gain a better understanding of the role of NCC in sodium and fluid volume homeostasis and in the pathogenesis of Gitelman's syndrome, we used gene targeting to prepare an NCC-deficient mouse. Null mutant (Ncc-/-) mice appear healthy and are normal with respect to acid-base balance, plasma electrolyte concentrations, serum aldosterone levels, and blood pressure. Ncc-/- mice retain Na+ as well as wild-type mice when fed a Na+-depleted diet; however, after 2 weeks of Na+ depletion the mean arterial blood pressure of Ncc-/- mice was significantly lower than that of wild-type mice. In addition, Ncc-/- mice exhibited increased renin mRNA levels in kidney, hypomagnesemia and hypocalciuria, and morphological changes in the distal convoluted tubule. These data indicate that the loss of NCC activity in the mouse causes only subtle perturbations of sodium and fluid volume homeostasis, but renal handling of Mg2+ and Ca2+ are altered, as observed in Gitelman's syndrome.     

Enhanced Na+/H+ exchange in Cushing's syndrome reflects functional hypermineralocorticoidism

BACKGROUND: Patients with Cushing's syndrome exhibit a bimodal distribution of maximal rates of the erythrocyte amiloride-sensitive Na+/H+ exchange (NHE). Enhanced erythrocyte NHE has recently been found in patients with primary aldosteronism. OBJECTIVE: To test the hypothesis that occult hypermineralocorticoidism in a subset of patients with Cushing's syndrome is responsible for the greater than normal NHE. METHODS: NHE was measured as maximal initial rate (Vmax) of amiloride-inhibited efflux of H+ into an alkaline Na+-containing medium, for 47 patients with hypercortisolism (20 with pituitary adenomas, 18 with adrenal adenomas, and nine with ectopic production of adrenocorticotropin). Clinical appearance, blood pressure levels, plasma aldosterone and deoxycorticosterone levels, serum electrolytes, and urine (tetrahydrocortisol plus 5-alpha-tetrahydrocortisol) : tetrahydrocortisone ratios were assessed for all patients. Twenty patients (10 with greater than normal NHE and 10 with low-to-normal NHE) were randomly selected from 47 patients with hypercortisolism, and treated with 200 mg/day spironolactone for 7 days. NHE in these patients was assessed before starting the treatment and 2 days after its cessation. RESULTS: Greater than normal NHE (Vmax) was associated with peripheral edema, high diastolic blood pressure, hypokalemia, and high urine (tetrahydrocortisol plus 5-alpha-tetrahydrocortisol) : tetrahydrocortisone ratios. The enhanced NHE was rapidly normalized by treatment with spironolactone. CONCLUSION: Erythrocyte NHE in patients with hypercortisolism and functional hypermineralocorticoidism is greater than normal due to incomplete peripheral conversion of cortisol (which binds to mineralocorticoid receptors) into metabolically inactive cortisone.     

Carbachol-induced increase of Na+/H+ antiport and recruitment of Na+,K(+)-ATPase in rabbit lacrimal acini

Parallel arrays of Na+/H+ and Cl-/HCO3- antiporters are believed to catalyze the first step of transepithelial electrolyte secretion in lacrimal glands by coupling Na+ and Cl- influxes across acinar cell basolateral membranes. Tracer uptake methods were used to confirm the presence of Na+/H+ antiport activity in membrane vesicles isolated from rabbit lacrimal gland fragments. Outwardly-directed H+ gradients accelerated 22Na+ uptake, and amiloride inhibited 96% of the H+ gradient-dependent 22Na+ flux. Amiloride-sensitive 22Na+ influx was half-maximal at an extravesicular Na+ concentration of 14 mM. In vitro stimulation of isolated lacrimal acini with 10 microM carbachol for 30 min increased Na+/H+ antiport activity of a subsequently isolated basolateral membrane sample 2.5-fold, but it did not significantly affect Na+/H+ antiport activity measured in intracellular membrane samples. The same treatment increased basolateral membrane Na+,K(+)-ATPase activity 1.4-fold; this increase could be accounted for by decreases in the Na+,K(+)-ATPase activities of intracellular membranes. Thus, it appears that cholinergic stimulation causes recruitment of additional Na+,K(+)-ATPase pump units to the acinar cell basolateral plasma membrane. The mechanistic basis of the increase in basolateral membrane Na+/H+ antiport activity remains unclear.     

Structural requirements for potential Na/H exchange inhibitors obtained from quantitative structure-activity relationships of monocyclic and bicyclic aroylguanidines

The quantitative structure-activity relationship (QSAR) of N-(3-amino-6-chloro-5-ethylisopropylaminopyrazine-4-carbonyl) guanidine (EIPA) 1ac and its derivatives as Na/H exchange inhibitors was analyzed using th steric parameters and an indicator variable. The results indicated that bicyclic aroylguanidines might have Na/H exchange inhibitory activity. Therefore, various bicyclic aroylguanidines were synthesized and tested for Na/H exchange inhibitory activity. The QSAR study of the bicyclic aroylguanidines showed that hydrophobic bicyclic rings seemed to be preferable for potent activity. The hydrophobicity of the aroyl ring moiety was thought to be particularly important. Thus, the QSAR of EIPA and its derivatives was re-analyzed using hydrophobicity and steric parameters. The results indicated that high hydrophobicity of the pseudo-ring moiety and a substituent of appropriate length at the position corresponding to the 5-position of the naphthalene ring enhance the activity. As expected from the results, 5-bromo-2-naphthoylguanidine 3b and 5-methoxy-2-naphthoylguanidine 3c exhibited strong activity. These findings will be helpful to design new, potent Na/H exchange inhibitors.     

Functional communication between cardiac ATP-sensitive K+ channel and Na/K ATPase

Insecticide resistance often is blamed for failures of insecticides to control cat fleas, Ctenocephalides felis (Bouché). Yet the genetics and adaptive advantage of resistance traits remain unexamined. Lethal doses of insecticides that kill 50% of the population fluctuate 7-fold within a cat flea strain. Many reports of flea resistance may be attributable to variable mortality from effects of solvents, substrates, humidities, temperatures, colonization, and ages of fleas. Resistance ratios (ratios of lethal doses of a resistant to a susceptible strain) are < 690-fold in fleas; lower than many other arthropods. This, plus strain variability, hinders resistance detection. Relationships between resistance levels, control failures, and health threats are unclear. Insensitive acetylcholinesterase, knockdown recovery, glutathione transferase conjugation, and mixed function oxidase/cytochrome P450 are demonstrated resistance mechanisms in cat fleas. Ecological genetics of resistance in cat fleas probably involves flea transfer among hosts, host movements, refugia, founder effects, and mortality from abiotic factors. Understanding cat flea resistance requires population monitoring before, during, and after insecticide treatments using conventional and rapid molecular bioassays. Sustained insecticide release devices such as flea collars and long-lived insecticide residues for premises possibly contribute to the development of resistance. New systemic and topical insecticides, especially when given prophylactically, may act similarly. Eliminating insecticides prevents insecticide resistance but necessitates application of biorational tactics incorporating mechanical, environmental, and cultural controls. Using high temperatures, low humidities, host grooming and such tactics as decreasing doses, increasing action thresholds, rotating insecticides, and leaving spatial and temporal refugia may suppress cat flea resistance.     

Erythrocyte Na/K ATPase activity and diabetes: relationship with C-peptide level

The purpose of this study is to clarify the volume effect of epidural saline injection 20 min after spinal anesthesia. Thirty patients undergoing combined spinal and epidural anesthesia for orthopedic surgery were randomly divided into two groups: a control group (n = 15) and a saline group (n = 15). In the control group, 2% lidocaine 3 ml with 0.4% tetracaine was injected into the subarachnoid space from L 4-5 interspace using Durasafe (Becton Dickinson, USA) and saline was not injected into the epidural space. In the saline group, saline 10 ml was injected through an epidural catheter 20 min after spinal anesthesia. The levels of analgesia 20 min after spinal anesthesia were not significantly different between the groups. However, the levels of analgesia 3, 5, 10, 40 and 100 min after epidural saline injection in the saline group were significantly higher than those in the control group (P < 0.05). The highest analgesic level was obtained 10 min after epidural saline injection and reached to T 4.3 +/- 1.1. In conclusion, epidural saline injection increases the analgesic level 20 min after spinal anesthesia because of the volume effect.     

Hypokalaemic alkalosis, acquired Gitelman''s and Bartter''s syndrome in chronic sialoadenitis

The use of a glucose biosensor coupled to microdialysis sampling in a flow injection analysis system is described to follow the growth of Escherichia coli in a glucose-containing liquid culture medium. The experimental set-up permitted a throughput rate of 25 samples h-1. Growth curves were modelled by a modified Gompertz equation, which permitted the determination of lag time and maximum specific growth rate. The time required to produce an appreciable variation in the biosensor response (minimum detection time, MDT) was determined. A plot of MDT versus microbial concentration was found to be linear in the range 10(6)-10(10) colony forming units (cfu) ml-1. A microbial concentration of 10(6) cfu ml-1 can be detected after about 5 h.     

Hoe 694, a new Na+/H+ exchange inhibitor and its effects in cardiac ischaemia

1. The benzoylguanidine derivative Hoe 694 ((3-methylsulphonyl-4- piperidino-benzoyl) guanidine methanesulphonate) was characterized as an inhibitor of Na+/H+ exchange in rabbit erythrocytes, rat platelets and bovine endothelial cells. The potency of the compound was slightly lower or comparable to ethylisopropyl amiloride (EIPA). 2. To investigate a possible cardioprotective role of the Na+/H+ exchange inhibitor Hoe 694, rat isolated working hearts were subjected to ischaemia and reperfusion. In these experiments all untreated hearts suffered ventricular fibrillation on reperfusion. Addition of 10(-7) M Hoe 694 to the perfusate almost abolished reperfusion arrhythmias in the rat isolated working hearts. 3. Hoe 694 reduced the release of lactate dehydrogenase (LDH) and creatine kinase (CK), which are indicators of cellular damage during ischaemia, into the venous effluent of the hearts by 60% and 54%, respectively. 4. The tissue content of glycogen at the end of the experiments was increased by 60% and the high energy phosphates ATP and creatine phosphate were increased by 240% and 270% respectively in the treated hearts as compared to control hearts. 5. Antiischaemic effects of the Na+/H+ exchange inhibitor, Hoe 694, were investigated in a second experiment in anaesthetized rats undergoing coronary artery ligation. In these animals, pretreatment with Hoe 694 caused a dose-dependent reduction of ventricular premature beats and ventricular tachycardia as well as a complete suppression of ventricular fibrillation down to doses of 0.1 mg kg-1, i.v. Blood pressure and heart rate remained unchanged. 6. We conclude that the new Na+/H+ exchange inhibitor, Hoe 694, shows cardioprotective and antiarrhythmic effects in ischaemia and reperfusion in rat isolated hearts and in anaesthetized rats. In view of the role which Na+/H+ exchange seems to play in the pathophysiology of cardiac ischaemia these effects could probably be attributed to Na+/H+ exchange inhibition.     

Hydrogen peroxide decreases pHi in human aortic endothelial cells by inhibiting Na+/H+ exchange

Postischemic endothelial dysfunction may occur as a result of the effects of endogenous oxidants like hydrogen peroxide. Since endothelium-dependent vasodilator function may be affected by pHi, the effect of hydrogen peroxide on endothelial pHi was examined. Hydrogen peroxide (100 micromol/L for 10 minutes) decreased pHi from 7.24+/-0.01 to 7.02+/-0.02 and inhibited recovery from an ammonium chloride-induced intracellular acid load in carboxy SNARF 1 (c-SNARF 1)-loaded human aortic endothelial cells in bicarbonate-free solution. Prior inhibition of Na+/H+ exchange with 5-(N-ethyl-N-isopropyl)amiloride (10 micromol/L), by removal of extracellular Na+, or by glycolytic inhibition with iodoacetic acid blocked the subsequent effect of hydrogen peroxide on pHi. A 2-minute exposure to 100 micromol/L H2O2 decreased intracellular ATP levels by approximately 40%; this was prevented by 3-aminobenzamide and nicotinamide (1 mmol/L each), inhibitors of the DNA repair enzyme poly(ADP-ribose) polymerase. Both 3-aminobenzamide and nicotinamide significantly inhibited the hydrogen peroxide-induced intracellular acidification and the effect of hydrogen peroxide on recovery from an intracellular acid load. Hydrogen peroxide decreases pHi in human endothelial cells by inhibiting Na+/H+ exchange. This appears to be mediated by activation of the DNA repair enzyme poly(ADP-ribose) polymerase and subsequent depletion of intracellular ATP. Since a decrease in pHi in this range may alter the activity of NO synthase or affect the synthesis of vasodilator prostaglandins, the effect of hydrogen peroxide on the endothelial Na+/H+ exchanger may be important in the pathogenesis of postischemic endothelial dysfunction.     

Genetic factors, Na K ATPase activity and neuropathy in diabetics]

A genetic predisposition to develop a polyneuropathy in case of diabetes seems to exist. Some ethnic groups such as North Africans are prone to develop a diabetic polyneuropathy. To identify this predisposition could help in targeting a preventive treatment. We have observed that red cell Na/K ATPase activity was lower among diabetic patients than controls and even lower when diabetic neuropathy was present. Now an impaired NA/K ATPase activity has been implicated in the pathogenesis of diabetic neuropathy and ethnic differences in this enzyme activity have been demonstrated. For these reasons, we have compared red cell Na/K ATPase activity of European and North African individuals with or without diabetes and in case of diabetes with or without neuropathy. Among European subjects, Na/K ATPase activity was higher in 46 control subjects than in 84 insulin-dependent diabetic patients (405 +/- 16 nmol.mg Prot-1h-1 versus 282 +/- 10 p. < 0.05) and in the diabetic group Na/K ATPase activity was lower in the patients presenting with neuropathy (242 +/- 19 versus 323 +/- 12 p. < 0.05). The mean red cell Na/K ATPase activity was lower in 16 North African control subjects than in their European counterparts (296 +/- 26 p. < 0.05). The same observation was made when comparing 24 North Africans insulin dependent diabetic patients to the European diabetics (246 +/- 20 p. < 0.05). A low Na/K ATPase activity appears to be a risk marker of diabetic neuropathy. It could explain the propensity of North African patients to develop this diabetic complication. A restriction polymorphism exist on the first intron of the ATP1 A1 gene coding for the ATPase alpha 1 isoform. This isoform is preponderent in the nervous tissue and exclusive in red cells. Among European diabetic individuals, the presence of the restricted allele is strongly associated to diabetic neuropathy, confering a relative risk of 6.5 (95%, confidence interval 3.3-13). The restricted allele is associated to a lower Na/K ATPase activity but only among diabetic patients and not in control subjects. This fact suggests an interaction between genetic factors (the restriction polymorphism of ATP1 A1 gene) and environmental factors (diabetes) to induce a decrease in Na/K ATPase activity which in turn could favor the development of diabetic neuropathy. Among North African individuals the impairement of Na/K ATPase activity is not explained by the presence of this polymorphism. Other genetic factors remain to be identified.     

Role of Na+/H+ exchange in the recovery of contractility during hypercapnia in cat papillary muscles

Cholesterol reduction reduces ischaemic cardiovascular morbidity and mortality in the asymptomatic healthy population as well as in those with known coronary artery disease. Angiographic studies have also demonstrated regression of atherosclerotic plaques as well as retardation of new atheroma formation with such therapy. Yet, there is a consistent inability to reduce overall mortality in cholesterol-lowering drug trials. An excess of suicide, homicide and violence has been attributed to cholesterol reduction interfering with membrane lipids and receptors, leading to aggressive behaviour. The risk and benefits of cholesterol reduction must thus be weighed in the individual patient; it is more useful in those with known coronary artery disease who are at high risk of subsequent ischaemic cardiovascular events.     

Droplet phenomena in the Ni/Na/D2EHPA/H2O system

Droplet behavior in the liquid-liquid extraction of nickel by mixtures of the sodium and hydrogen forms of di-2-ethylhexylphosphoric acid in toluene is reported. Mass transfer to single drops of organic phase dispersed in the aqueous has been measured. When the aqueous phase has low electrolyte concentration, visible wakes appear which are due to emulsification of the sodium salt. Mass transfer of the nickel is accompanied by transfer of water and, in some instances, by the emulsification process. The rate of mass transfer is fast and ensures some 50 pet approach to equilibrium in the residence times studied here. The effect of tributylphosphate is to improve the transfer rate but, for low electrolyte concentrations, the modifier does not remove the wakes.     

Tension generation and increase in voltage-activated Na+ current by crotamine

It is suggested that working memory comprises a system for the temporary storage and manipulation of information, forming an important link between perception and controlled action. Evidence is presented for a three-component model, comprising an attentional control system, the central executive, and two subsidiary slave systems. One of these the, the visuo-spatial sketch pad holds and manipulates spatial information, while the other, the phonological loop performs a similar function for auditory and speech-based information. Evidence is presented for the view that the phonological loop has evolved as a mechanism to facilitate the acquisition of language.     

Effect of inhibitors of Na+/H+-exchange and gastric H+/K+ ATPase on cell volume, intracellular pH and migration of human polymorphonuclear leucocytes

1. Stimulation of chemotaxis of human polymorphonuclear leucocytes (PMNs) with the chemoattractive peptide fMLP (N-formyl-Met-Leu-Phe) is paralleled by profound morphological and metabolic alterations like changes of intracellular pH (pHi) and cell shape. The present study was performed to investigate the interrelation of cell volume (CV) regulatory ion transport, pHi and migration of fMLP stimulated PMNs. 2. Addition of fMLP to PMNs stimulated directed migration in Boyden chamber assays and was accompanied by rapid initial intracellular acidification and cell swelling. 3. Inhibition of the Na+/H+ exchanger suppressed fMLP stimulated cell migration, accelerated the intracellular acidification and inhibited the fMLP-induced cell swelling. 4. Step omission of extracellular Na+ caused intracellular acidification, which was accelerated by subsequent addition of gastric H+/K+ ATPase inhibitor SCH 28080, or by omission of extracellular K+ ions. In addition Na+ removal caused cell swelling, which was further enhanced by fMLP. 5. H+/K+ATPase inhibitors omeprazole and SCH 28080 inhibited stimulated migration and blunted the fMLP-induced increase in CV. 6. Increasing extracellular osmolarity by addition of mannitol to the extracellular solution caused cell shrinkage followed by regulatory volume increase, partially due to activation of the Na+/H+ exchanger. In fMLP-stimulated cells the CV increase was counteracted by simultaneous addition of mannitol. Under these conditions the fMLP stimulated migration was inhibited. 7. The antibacterial activity of PMNs was not modified by Hoe 694 or omeprazole. 8. Western analysis with a monoclonal anti gastric H+/K+ ATPase beta-subunit antibody detected a glycosylated 35 kD core protein in lysates of mouse and human gastric mucosa as well as in human PMNs. 9. The results indicate that fMLP leads to cell swelling of PMNs due to activation of the Na+/H+ exchanger and a K+-dependent H+-extruding mechanism, presumably an H+/K+ ATPase. Inhibition of these ion transporters suppresses the increase in CV and precludes PMNs from stimulated migration.