M-wave changes caused by brief voluntary and stimulated isometric contractions.

INTRODUCTION: Under isometric conditions, the increase in muscle force is accompanied by a reduction in the fibers' length. The effects of muscle shortening on the compound muscle action potential (M wave) have so far been investigated only by computer simulation. This study was undertaken to assess experimentally the M-wave changes caused by brief voluntary and stimulated isometric contractions. METHODS: Two different methods of inducing muscle shortening under isometric condition were adopted: (1) applying a brief (1 s) tetanic contraction and (2) performing brief voluntary contractions of different intensities. In both methods, supramaximal stimulation was applied to the brachial plexus and femoral nerves to evoke M waves. In the first method, electrical stimulation (20 Hz) was delivered with the muscle at rest, whereas in the second, stimulation was applied while participants performed 5-s stepwise isometric contractions at 10, 20, 30, 40, 50, 60, 70, and 100% MVC. The amplitude and duration of the first and second M-wave phases were computed. RESULTS: The main findings were: (1) on application of tetanic stimulation, the amplitude of the M-wave first phase decreased (~ 10%, P < 0.05), that of the second phase increased (~ 50%, P < 0.05), and the M-wave duration decreased (~ 20%, P < 0.05) across the first five M waves of the tetanic train and then plateaued for the subsequent responses; (2) when superimposing a single electrical stimulus on muscle contractions of increasing forces, the amplitude of the M-wave first phase decreased (~ 20%, P < 0.05), that of the second phase increased (~ 30%, P < 0.05), and M-wave duration decreased (~ 30%, P < 0.05) as force was raised from 0 to 60-70% MVC force. CONCLUSIONS: The present results will help to identify the adjustments in the M-wave profile caused by muscle shortening and also contribute to differentiate these adjustments from those caused by muscle fatigue and/or changes in Na+-K+ pump activity.

Bimodal modulation of short-term motor memory via dynamic sodium pumps in a vertebrate spinal cord.

Dynamic neuronal Na+/K+ pumps normally only respond to intense action potential firing owing to their low affinity for intracellular Na+. Recruitment of these Na+ pumps produces a post-activity ultraslow afterhyperpolarization (usAHP) up to ∼10 mV in amplitude and ∼60 s in duration, which influences neuronal properties and future network output. In spinal motor networks, the usAHP underlies short-term motor memory (STMM), reducing the intensity and duration of locomotor network output in a manner dependent on the interval between locomotor bouts. In contrast to tonically active Na+ pumps that help set and maintain the resting membrane potential, dynamic Na+ pumps are selectively antagonized by low concentrations of ouabain, which, we show, blocks both the usAHP and STMM. We examined whether dynamic Na+ pumps and STMM can be influenced by neuromodulators, focusing on 5-HT and nitric oxide. Bath-applied 5-HT alone had no significant effect on the usAHP or STMM. However, this is due to the simultaneous activation of two distinct 5-HT receptor subtypes (5-HT7 and 5-HT2a) that have opposing facilitatory and suppressive influences, respectively, on these two features of the locomotor system. Nitric oxide modulation exerts a potent inhibitory effect that can completely block the usAHP and erase STMM. Using selective blockers of 5-HT7 and 5-HT2a receptors and a nitric oxide scavenger, PTIO, we further provide evidence that the two modulators constitute an endogenous control system that determines how the spinal network self-regulates the intensity of locomotor output in light of recent past experience.

The Role of Na+/K+-ATPase in the Development of Hyponatrenemia under Conditions of Hypoxic Stress in Patients with SARS-CoV-2 Infection.

We studied laboratory parameters of patients with COVID-19 against the background of chronic pathologies (cardiovascular pathologies, obesity, type 2 diabetes melitus, and cardiovascular pathologies with allergy to statins). A decrease in pH and a shift in the electrolyte balance of blood plasma were revealed in all studied groups and were most pronounced in patients with cardiovascular pathologies with allergy to statin. It was found that low pH promotes destruction of lipid components of the erythrocyte membranes in patients with chronic pathologies, which was seen from a decrease in Na+/K+-ATPase activity and significant hyponatrenemia. In patients with cardiovascular pathologies and allergy to statins, erythrocyte membranes were most sensitive to a decrease in pH, while erythrocyte membranes of obese patients showed the greatest resistance to low pH and oxidative stress.

[Different Membrane Environments Generate Multiple Functions of P-type Ion Pumps].

P-type ion pumps (P-type ATPases) are involved in various fundamental biological processes. For example, the gastric proton pump (H+,K+-ATPase) and sodium pump (Na+,K+-ATPase) are responsible for secretion of gastric acid and maintenance of cell membrane potential, respectively. In this review, we summarize three topics of our studies. The first topic is gastric H+,K+-ATPase associated with Cl--transporting proteins (Cl-/H+ exchanger ClC-5 and K+-Cl- cotransporter KCC4). In gastric parietal cells, we found that ClC-5 is predominantly expressed in intracellular tubulovesicles and that KCC4 is predominantly expressed in the apical membrane. Gastric acid (HCl) secretion may be accomplished by the two different complexes of H+,K+-ATPase and Cl--transporting protein. The second topic focuses on the Na+,K+-ATPase α1-isoform (α1NaK) associated with the volume-regulated anion channel (VRAC). In the cholesterol-enriched membrane microdomains of human cancer cells, we found that α1NaK has a receptor-like (non-pumping) function and that binding of low concentrations (nM level) of cardiac glycosides to α1NaK activates VRAC and exerts anti-cancer effects without affecting the pumping function of α1NaK. The third topic is the Na+,K+-ATPase α3-isoform (α3NaK) in human cancer cells. We found that α3NaK is abnormally expressed in the intracellular vesicles of attached cancer cells and that the plasma membrane translocation of α3NaK upon cell detachment contributes to the survival of metastatic cancer cells. Our results indicate that multiple functions of P-type ion pumps are generated by different membrane environments and their associated proteins.

Multiomic analysis of the Arabian camel (Camelus dromedarius) kidney reveals a role for cholesterol in water conservation.

The Arabian camel (Camelus dromedarius) is the most important livestock animal in arid and semi-arid regions and provides basic necessities to millions of people. In the current context of climate change, there is renewed interest in the mechanisms that enable camelids to survive in arid conditions. Recent investigations described genomic signatures revealing evolutionary adaptations to desert environments. We now present a comprehensive catalogue of the transcriptomes and proteomes of the dromedary kidney and describe how gene expression is modulated as a consequence of chronic dehydration and acute rehydration. Our analyses suggested an enrichment of the cholesterol biosynthetic process and an overrepresentation of categories related to ion transport. Thus, we further validated differentially expressed genes with known roles in water conservation which are affected by changes in cholesterol levels. Our datasets suggest that suppression of cholesterol biosynthesis may facilitate water retention in the kidney by indirectly facilitating the AQP2-mediated water reabsorption.

FXYD protein isoforms differentially modulate human Na/K pump function.

Tight regulation of the Na/K pump is essential for cellular function because this heteromeric protein builds and maintains the electrochemical gradients for Na+ and K+ that energize electrical signaling and secondary active transport. We studied the regulation of the ubiquitous human α1ß1 pump isoform by five human FXYD proteins normally located in muscle, kidney, and neurons. The function of Na/K pump α1ß1 expressed in Xenopus oocytes with or without FXYD isoforms was evaluated using two-electrode voltage clamp and patch clamp. Through evaluation of the partial reactions in the absence of K+ but presence of Na+ in the external milieu, we demonstrate that each FXYD subunit alters the equilibrium between E1P(3Na) and E2P, the phosphorylated conformations with Na+ occluded and free from Na+, respectively, thereby altering the apparent affinity for Na+. This modification of Na+ interaction shapes the small effects of FXYD proteins on the apparent affinity for external K+ at physiological Na+. FXYD6 distinctively accelerated both the Na+-deocclusion and the pump-turnover rates. All FXYD isoforms altered the apparent affinity for intracellular Na+ in patches, an effect that was observed only in the presence of intracellular K+. Therefore, FXYD proteins alter the selectivity of the pump for intracellular ions, an effect that could be due to the altered equilibrium between E1 and E2, the two major pump conformations, and/or to small changes in ion affinities that are exacerbated when both ions are present. Lastly, we observed a drastic reduction of Na/K pump surface expression when it was coexpressed with FXYD1 or FXYD6, with the former being relieved by injection of PKA's catalytic subunit into the oocyte. Our results indicate that a prominent effect of FXYD1 and FXYD6, and plausibly other FXYDs, is the regulation of Na/K pump trafficking.

Role of the Intracellular Sodium Homeostasis in Chemotaxis of Activated Murine Neutrophils.

The importance of the intracellular Ca2+ concentration ([Ca2+]i) in neutrophil function has been intensely studied. However, the role of the intracellular Na+ concentration ([Na+]i) which is closely linked to the intracellular Ca2+ regulation has been largely overlooked. The [Na+]i is regulated by Na+ transport proteins such as the Na+/Ca2+-exchanger (NCX1), Na+/K+-ATPase, and Na+-permeable, transient receptor potential melastatin 2 (TRPM2) channel. Stimulating with either N-formylmethionine-leucyl-phenylalanine (fMLF) or complement protein C5a causes distinct changes of the [Na+]i. fMLF induces a sustained increase of [Na+]i, surprisingly, reaching higher values in TRPM2-/- neutrophils. This outcome is unexpected and remains unexplained. In both genotypes, C5a elicits only a transient rise of the [Na+]i. The difference in [Na+]i measured at t = 10 min after stimulation is inversely related to neutrophil chemotaxis. Neutrophil chemotaxis is more efficient in C5a than in an fMLF gradient. Moreover, lowering the extracellular Na+ concentration from 140 to 72 mM improves chemotaxis of WT but not of TRPM2-/- neutrophils. Increasing the [Na+]i by inhibiting the Na+/K+-ATPase results in disrupted chemotaxis. This is most likely due to the impact of the altered Na+ homeostasis and presumably NCX1 function whose expression was shown by means of qPCR and which critically relies on proper extra- to intracellular Na+ concentration gradients. Increasing the [Na+]i by a few mmol/l may suffice to switch its transport mode from forward (Ca2+-efflux) to reverse (Ca2+-influx) mode. The role of NCX1 in neutrophil chemotaxis is corroborated by its blocker, which also causes a complete inhibition of chemotaxis.

[Study of the Mechanisms of Maintaining the Transparency of the Lens and Treatment of Its Related Diseases for Making Anti-cataract and/or Anti-presbyopia Drugs].

The lens of the eye is an avascular and anuclear tissue that serves to focus objects on the retina. Cataract is opacity within the clear lens that changes the transparency and refractive index of the lens causing significant visual impairments. These impairments can severely restrict the ability to carry out daily activities. Cataracts is common among elderly person occurring in more than 80% of patients aged 80 or older. Notably, we have recently identified key compounds that are effective against cataract formation. Presbyopia is also an ocular disease that typically develops in people over the age of 45 while affecting almost 100% of people over the age of 65. Recent research suggests that age-related changes in hydrostatic pressure of the lens controlled by Na/K ATPase contribute to the development of presbyopia. In the lens, Na/K ATPase has been shown to be regulated by transient receptor potential cation channels, vanilloid 1 (TRPV1) and 4, thus suggesting the potential role of TRPV1 and TRPV4 in the development of presbyopia. This review article summarizes data obtained from our laboratory with my colleagues highlighting the critical role of aquaporin 0 (AQP0) in maintaining a healthy lens redox environment, key molecules that delay the onset of cataract in vivo, as well as potential mechanisms of lens hydrostatic pressure control that may be associated with presbyopia.

The α2 Na+/K+-ATPase isoform mediates LPS-induced neuroinflammation.

Na+/K+-ATPase is a transmembrane ion pump that is essential for the maintenance of ion gradients and regulation of multiple cellular functions. Na+/K+-ATPase has been associated with nuclear factor kappa B (NFκB) signalling, a signal associated with lipopolysaccharides (LPSs)-induced immune response in connection with activated Toll-like receptor 4 (TLR4) signalling. However, the contribution of Na+/K+-ATPase to regulating inflammatory responses remains elusive. We report that mice haploinsufficient for the astrocyte-enriched α2Na+/K+-ATPase isoform (α2+/G301R mice) have a reduced proinflammatory response to LPS, accompanied by a reduced hypothermic reaction compared to wild type litter mates. Following intraperitoneal injection of LPS, gene expressions of Tnf-α, Il-1ß, and Il-6 was reduced in the hypothalamus and hippocampus from α2+/G301R mice compared to α2+/+ littermates. The α2+/G301R mice experienced increased expression of the gene encoding an antioxidant enzyme, NRF2, in hippocampal astrocytes. Our findings indicate that α2Na+/K+-ATPase haploinsufficiency negatively modulates LPS-induced immune responses, highlighting a rational pharmacological target for reducing LPS-induced inflammation.

Targeting Cardiac Myocyte Na+-K+ Pump Function With ß3 Adrenergic Agonist in Rabbit Model of Severe Congestive Heart Failure.

BACKGROUND: Abnormally high cytosolic Na+ concentrations in advanced heart failure impair myocardial contractility. Stimulation of the membrane Na+-K+ pump should lower Na+ concentrations, and the ß3 adrenoceptor (ß3 AR) mediates pump stimulation in myocytes. We examined if ß3 AR-selective agonists given in vivo increase myocyte Na+-K+ pump activity and reverse organ congestion in severe heart failure (HF). METHODS: Indices for HF were lung-, heart-, and liver: body weight ratios and ascites after circumflex coronary artery ligation in rabbits. Na+-K+ pump current, Ip, was measured in voltage-clamped myocytes from noninfarct myocardium. Rabbits were treated with the ß3 AR agonists CL316,243 or ASP9531, starting 2 weeks after coronary ligation. RESULTS: Coronary ligation caused ascites in most rabbits, significantly increased lung-, heart-, and liver: body weight ratios, and decreased Ip relative to that for 10 sham-operated rabbits. Treatment with CL316,243 for 3 days significantly reduced lung-, heart-, and liver: body weight ratios and prevalence of ascites in 8 rabbits with HF relative to indices for 13 untreated rabbits with HF. It also increased Ip significantly to levels of myocytes from sham-operated rabbits. Treatment with ASP9531 for 14 days significantly reduced indices of organ congestion in 6 rabbits with HF relative to indices of 6 untreated rabbits, and it eliminated ascites. ß3 AR agonists did not significantly change heart rates or blood pressures. CONCLUSIONS: Parallel ß3 AR agonists-induced reversal of Na+-K+ pump inhibition and indices of congestion suggest pump inhibition is a useful target for treatment with ß3 AR agonists in congestive HF.

Central Role for Adipocyte Na,K-ATPase Oxidant Amplification Loop in the Pathogenesis of Experimental Uremic Cardiomyopathy.

BACKGROUND: Oxidative stress in adipocyte plays a central role in the pathogenesis of obesity as well as in the associated cardiovascular complications. The putative uremic toxin indoxyl sulfate induces oxidative stress and dramatically alters adipocyte phenotype in vitro. Mice that have undergone partial nephrectomy serve as an experimental model of uremic cardiomyopathy. This study examined the effects on adipocytes of administering a peptide that reduces oxidative stress to the mouse model. METHODS: A lentivirus vector introduced the peptide NaKtide with an adiponectin promoter into the mouse model of experimental uremic cardiomyopathy, intraperitoneally. Then adipocyte-specific expression of the peptide was assessed for mice fed a standard diet compared with mice fed a western diet enriched in fat and fructose. RESULTS: Partial nephrectomy induced cardiomyopathy and anemia in the mice, introducing oxidant stress and an altered molecular phenotype of adipocytes that increased production of systemic inflammatory cytokines instead of accumulating lipids, within 4 weeks. Consumption of a western diet significantly worsened the adipocyte oxidant stress, but expression of NaKtide in adipocytes completely prevented the worsening. The peptide-carrying lentivirus achieved comparable expression in skeletal muscle, but did not ameliorate the disease phenotype. CONCLUSIONS: Adipocyte-specific expression of NaKtide, introduced with a lentiviral vector, significantly ameliorated adipocyte dysfunction and uremic cardiomyopathy in partially nephrectomized mice. These data suggest that the redox state of adipocytes controls the development of uremic cardiomyopathy in mice subjected to partial nephrectomy. If confirmed in humans, the oxidative state of adipocytes may be a therapeutic target in chronic renal failure.

Ouabain-regulated phosphoproteome reveals molecular mechanisms for Na+, K+-ATPase control of cell adhesion, proliferation, and survival.

The ion pump Na+, K+-ATPase (NKA) is a receptor for the cardiotonic steroid ouabain. Subsaturating concentration of ouabain triggers intracellular calcium oscillations, stimulates cell proliferation and adhesion, and protects from apoptosis. However, it is controversial whether ouabain-bound NKA is considered a signal transducer. To address this question, we performed a global analysis of protein phosphorylation in COS-7 cells, identifying 2580 regulated phosphorylation events on 1242 proteins upon 10- and 20-min treatment with ouabain. Regulated phosphorylated proteins include the inositol triphosphate receptor and stromal interaction molecule, which are essential for initiating calcium oscillations. Hierarchical clustering revealed that ouabain triggers a structured phosphorylation response that occurs in a well-defined, time-dependent manner and affects specific cellular processes, including cell proliferation and cell-cell junctions. We additionally identify regulation of the phosphorylation of several calcium and calmodulin-dependent protein kinases (CAMKs), including 2 sites of CAMK type II-γ (CAMK2G), a protein known to regulate apoptosis. To verify the significance of this result, CAMK2G was knocked down in primary kidney cells. CAMK2G knockdown impaired ouabain-dependent protection from apoptosis upon treatment with high glucose or serum deprivation. In conclusion, we establish NKA as the coordinator of a broad, tightly regulated phosphorylation response in cells and define CAMK2G as a downstream effector of NKA.-Panizza, E., Zhang, L., Fontana, J. M., Hamada, K., Svensson, D., Akkuratov, E. E., Scott, L., Mikoshiba, K., Brismar, H., Lehtiö, J., Aperia, A. Ouabain-regulated phosphoproteome reveals molecular mechanisms for Na+, K+-ATPase control of cell adhesion, proliferation, and survival.

Na+-K+-ATPase and nka genes in spotted sea bass (Lateolabrax maculatus) and their involvement in salinity adaptation.

Euryhaline teleosts can survive in a wide salinity range via alteration of the molecular mechanisms to maintain internal ionic and osmotic balance in osmoregulatory organs such as gill，kidney and intestine. Na+/K+-ATPase (NKA), plays a crucial role in sustaining intracellular homeostasis and is characterized by association of multiple isoforms of α- and ß-subunits. To gain insight into the potential function of nka genes in salinity adaptation, 5 nkaα genes (nkaα1a, nkaα1b, nkaα2, nkaα3a, nkaα3b) and 7 nkaß genes (nkaß1a, nkaß1b, nkaß2a, nkaß2b, nkaß3a, nkaß3b and nkaß4) were identified from transcriptomic and genomic databases of Lateolabrax maculatus. The annotation and evolutionary footprint of these nka genes was revealed via the analysis of phylogenetic tree, gene synteny, copy numbers, exon-intron structures and motif compositions. The expressions of 12 nka genes in spotted sea bass was tested in ten tissues (kidney, gonad, stomach, intestine, gill, muscle, heart, spleen, liver and brain) and 6 genes (nkaα1a, nkaα1b, nkaα3a, nkaα3b, nkaß1b and nkaß2a) showed high expression in osmoregulatory organs. Furthermore, the responses of NKA and potential salinity-sensitive nka genes were examined under different salinity treatment (0 ppt, 12 ppt, 30 ppt, 45 ppt). Results showed that the enzyme activity of NKA was highest in gill and exhibited salinity dependent variation, with the highest activity identified in 45 ppt. Different nkaα/ß-isoforms showed their diverse responses to salinity changes and the expression of nka genes including nkaα1a, nkaα3b, nkaß1b in gill, nkaα3a in kidney and nkaß2a in intestine were transcriptionally regulated by altered salinity. Notably, the expression patterns of nkaα1a and nkaß1b in gill showed similar variation trend with NKA activity, suggesting that nkaα1a/ß1b could be the major function isoforms involved in primary ion transport during salinity adaptation. Our results provided insights into the roles of nkas in osmotic regulation and a theoretical basis for future studies that focus on detailed molecular mechanisms in salinity adaptation of euryhaline teleosts.

The footprints of mitochondrial impairment and cellular energy crisis in the pathogenesis of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and Fanconi's syndrome: A comprehensive review.

Fanconi's Syndrome (FS) is a disorder characterized by impaired renal proximal tubule function. FS is associated with a vast defect in the renal reabsorption of several chemicals. Inherited and/or acquired conditions seem to be connected with FS. Several xenobiotics including many pharmaceuticals are capable of inducing FS and nephrotoxicity. Although the pathological state of FS is well described, the exact underlying etiology and cellular mechanism(s) of xenobiotics-induced nephrotoxicity, serum electrolytes imbalance, and FS are not elucidated. Constant and high dependence of the renal reabsorption process to energy (ATP) makes mitochondrial dysfunction as a pivotal mechanism which could be involved in the pathogenesis of FS. The current review focuses on the footprints of mitochondrial impairment in the etiology of xenobiotics-induced FS. Moreover, the importance of mitochondria protecting agents and their preventive/therapeutic capability against FS is highlighted. The information collected in this review may provide significant clues to new therapeutic interventions aimed at minimizing xenobiotics-induced renal injury, serum electrolytes imbalance, and FS.

Involvement of the Na+ ,K+ -ATPase isoforms in control of cerebral perfusion.

NEW FINDINGS: What is the topic of this review? In this review, we consider the role of the Na+ ,K+ -ATPase in cerebrovascular function and how it might be changed in familial hemiplegic migraine type 2 (FHM2). The primary focus is involvement of the Na+ ,K+ -ATPase isoforms in regulation of cerebrovascular tone. What advances does it highlight? In this review, we discuss three overall distinct mechanisms whereby the Na+ ,K+ -ATPase might be capable of regulating cerebrovascular tone. Furthermore, we discuss how changes in the Na+ ,K+ -ATPase in cerebral arteries might affect brain perfusion and thereby be involved in the pathology of FHM2. ABSTRACT: Familial hemiplegic migraine type 2 (FHM2) has been characterized by biphasic changes in cerebral blood flow during a migraine attack, with initial hypoperfusion followed by abnormal hyperperfusion of the affected hemisphere. We suggested that FHM2-associated loss-of-function mutation(s) in the Na+ ,K+ -ATPase α2 isoform might be responsible for these biphasic changes in several ways. We found that reduced expression of the α2 isoform leads to sensitization of the contractile machinery to [Ca2+ ]i via Src kinase-dependent signal transduction. This change in sensitivity might be the underlying mechanism for both abnormally potentiated vasoconstriction and exaggerated vasorelaxation. Moreover, the functional significance of the Na+ ,K+ -ATPase α2 isoform in astrocytes provides for the possibility of elevated extracellular potassium signalling from astrocytic endfeet to the vascular wall in neurovascular coupling.

MiR-192-5p in the Kidney Protects Against the Development of Hypertension.

MicroRNA miR-192-5p is one of the most abundant microRNAs in the kidney and targets the mRNA for ATP1B1 (ß1 subunit of Na+/K+-ATPase). Na+/K+-ATPase drives renal tubular reabsorption. We hypothesized that miR-192-5p in the kidney would protect against the development of hypertension. We found miR-192-5p levels were significantly lower in kidney biopsy specimens from patients with hypertension (n=8) or hypertensive nephrosclerosis (n=32) compared with levels in controls (n=10). Similarly, Dahl salt-sensitive (SS) rats showed a reduced abundance of miR-192-5p in the renal cortex compared with congenic SS.13BN26 rats that had reduced salt sensitivity (n=9; P<0.05). Treatment with anti-miR-192-5p delivered through renal artery injection in uninephrectomized SS.13BN26 rats exacerbated hypertension significantly. Mean arterial pressure on a 4% NaCl high-salt diet at day 14 post anti-miR-192-5p treatment was 16 mm Hg higher than in rats treated with scrambled anti-miR (n=8 and 6; P<0.05). Similarly, Mir192 knockout mice on the high-salt diet treated with Ang II (angiotensin II) for 14 days exhibited a mean arterial pressure 22 mm Hg higher than wild-type mice (n=9 and 5; P<0.05). Furthermore, protein levels of ATP1B1 were higher in Dahl SS rats than in SS.13BN26 rats. Na+/K+-ATPase activity increased in the renal cortex of SS.13BN26 rats 9 days posttreatment with anti-miR-192-5p compared with that of control anti-miR treated rats. Intrarenal knockdown of ATP1B1 attenuated hypertension in SS.13BN26 rats with intrarenal knockdown of miR-192-5p. In conclusion, miR-192-5p in the kidney protects against the development of hypertension, which is mediated, at least in part, by targeting Atp1b1.

Alteration in branchial NKA and NKCC ion-transporter expression and ionocyte distribution in adult hilsa during up-river migration.

Hilsa (Tenualosa ilisha) is a clupeid that migrates from the off-shore area through the freshwater river for spawning. The purpose of this study was to investigate the involvement of branchial Na+/K+-ATPase (NKA) and Na+/K+/2Cl- cotransporter (NKCC) in maintaining ionic homeostasis in hilsa while moving across the salt barriers. Hilsa, migrating through marine and brackish waters, did not show any significant decline in NKA activity, plasma osmolality, and plasma ionic concentration. In contrast, all the parameters declined significantly, after the fish reached in freshwater zone of the river. Immunoblotting with NKA α antibody recognized two bands in gill homogenates. The intensity of the higher molecular NKA band decreased, while the other band subsequently increased accompanying the movement of hilsa from marine water (MW) to freshwater. Nevertheless, total NKA expression in marine water did not change prior to freshwater entry. NKCC expression was down-regulated in gill, parallel with NKA activity, as the fish approached to the freshwater stretch of river. The NKA α-1 and NKCC1 protein abundance decreased in freshwater individuals by 40% and 31%, respectively, compared to MW. NKA and NKCC1 were explicitly localized to branchial ionocytes and immunoreactive signal appeared throughout the cytoplasm except for the nucleus and the most apical region indicates a basolateral/tubular distribution. Immunoreactive ionocytes were distributed on the filaments and lamellae; lamellar ionocytes were more in number irrespective of habitat salinity. The decrease in salinity caused a slight reduction in ionocyte number, but not in size and the underlying distribution pattern did not alter. The overall results support previously proposed models that both the ion transporters are involved in maintaining ionic homeostasis and lamellar ionocytes may have the function in hypo-osmoregulation in migrating hilsa, unlike other anadromous teleosts.

[Features of the changes in lipid peroxidation and activity of Na+/K+-ATPase in the brain of the aged rats in the conditions of two-vessel cerebral ischemia/reperfusion.]

The success of preclinical neuroprotection studies depends on the model used in animal research. The methodological approaches developed on young animals and widely used for modeling cerebral ischemia/reperfusion injury may not be so effective or not suitable for its modeling on senescent animals, which usage is recommended for preclinical trials. The aim of this study was to investigate the age-related features on the effect of brain reperfusion with different duration (1 and 3 h) after 2-vessel forebrain ischemia on the level of lipid peroxidation (LPO) products and on the activity of Na+/K+-ATPase in the cerebral cortex of rats aged 22-24 months. We found a later accumulation of LPO products (3 h instead of 1 h after blood recirculation), specifically triene conjugates and Schiff bases, and a decrease in the activity of Na+/K+-ATPase in the cerebral cortex of aged rats compared to young animals. The data obtained reveal the difference in the molecular and physiological mechanisms of the development of disorders in the brain during ischemia/reperfusion in aged and young animals. The revealed differences in these mechanisms should be consider in developing and testing compounds, which will be further used for the treatment of elderly patients with stroke and ischemic brain damage.

Na+/K+ Balance and Transport Regulatory Mechanisms in Weedy and Cultivated Rice (Oryza sativa L.) Under Salt Stress.

BACKGROUND: Salinization is a primary abiotic stress constraining global plant growth and production. Weedy rice, though highly homologous to cultivated rice, is more salt tolerant during seed germination and seedling growth; we hypothesize that this is owing to ionic homeostasis and changes in the expression of genes encoding ion transport regulators. RESULTS: The four different genotypes of weedy (JYGY-1 and JYFN-4) and cultivated (Nipponbare and 9311) rice have different salt-tolerance during seed germination and seedling vegetative growth under salt stress. In this study, Na+ and Ca2+content increased in weedy and cultivated rice genotypes under salt stress while K+ and Mg2+decreased; however, JYGY-1 had the lowest Na+/K+ ratio of assessed genotypes. Genes in the high-affinity K+ transporter (HKT) and tonoplast sodium-hydrogen exchanger (NHX) families, and salt overly sensitive 1 (OsSOS1) have more than 98% homology in amino acid sequences between weedy and cultivated rice genotypes. Under salt stress, the HKT family members were differentially expressed in the roots and shoots of four different genotypes. However, the NHX family transcripts were markedly up-regulated in all genotypes, but there are significant differences between different genotypes. OsSOS1 was significantly up-regulated in roots, especially in JYGY-1genotype. CONCLUSIONS: The results showed that different genotypes had different germination and nutrient survival under salt stress, which was related to the difference of ion content and the difference of a series of ion transport gene expression. At the same time this study will provide new insight into the similarities and differences in ion homeostasis and gene regulatory mechanisms between weedy and cultivated rice under salt stress, which can aid in novel rice breeding and growth strategies.