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      Disturbed acid-base transport: an emerging cause of hypertension.

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          Abstract

          Genome-wide association studies and physiological investigations have linked alterations in acid-base transporters to hypertension. Accordingly, Na(+)-coupled HCO(-) 3-transporters, Na(+)/H(+)-exchangers, and anion-exchangers have emerged as putative mechanistic components in blood pressure disturbances. Even though hypertension has been studied extensively over the last several decades, the cause of the high blood pressure has in most cases not been identified. Renal, cardiovascular, and neuronal dysfunctions all seem to play a role in hypertension development but their relative importance and mutual interdependency are still being debated. Multiple functional and structural alterations have been described in patients and animals with hypertension but it is typically unclear whether they are causes or consequences of hypertension or represent mechanistically unrelated associations. Perturbed blood pressure regulation has been demonstrated in several animal models with disrupted expression of acid-base transporters; and reciprocally, disturbed acid-base transport function has been described in hypertensive individuals. In addition to regulating intracellular and extracellular pH, Na(+)-coupled HCO(-) 3-transport, Na(+)/H(+)-exchange, and anion-exchange also contribute to water and electrolyte balance in cells and systemically. Since acid-base transporters are widely expressed, alterations in transport activities likely affect multiple cell and organ functions, and it is a significant challenge to determine the mechanisms linking perturbed acid-base transport function to hypertension. It is the purpose of this review to evaluate the current evidence for involvement of acid-base transporters in hypertension development and discuss the cellular and integrative mechanisms, which may link changes in acid-base transport to blood pressure disturbances.

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          Most cited references108

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          Role of ion channels and transporters in cell migration.

          Cell motility is central to tissue homeostasis in health and disease, and there is hardly any cell in the body that is not motile at a given point in its life cycle. Important physiological processes intimately related to the ability of the respective cells to migrate include embryogenesis, immune defense, angiogenesis, and wound healing. On the other side, migration is associated with life-threatening pathologies such as tumor metastases and atherosclerosis. Research from the last ≈ 15 years revealed that ion channels and transporters are indispensable components of the cellular migration apparatus. After presenting general principles by which transport proteins affect cell migration, we will discuss systematically the role of channels and transporters involved in cell migration.
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            Renal and intestinal absorptive defects in mice lacking the NHE3 Na+/H+ exchanger.

            NHE3 is one of five plasma membrane Na+/H+ exchangers and is encoded by the mouse gene Slc9a3. It is expressed on apical membranes of renal proximal tubule and intestinal epithelial cells and is thought to play a major role in NaCl and HCO3- absorption. As the distribution of NHE3 overlaps with that of the NHE2 isoform in kidney and intestine, the function and relative importance of NHE3 in vivo is unclear. To analyse its physiological functions, we generated mice lacking NHE3 function. Homozygous mutant (Slc9a3-/-) mice survive, but they have slight diarrhoea and blood analysis revealed that they are mildly acidotic. HCO3- and fluid absorption are sharply reduced in proximal convoluted tubules, blood pressure is reduced and there is a severe absorptive defect in the intestine. Thus, compensatory mechanisms must limit gross perturbations of electrolyte and acid-base balance. Plasma aldosterone is increased in NHE3-deficient mice, and expression of both renin and the AE1 (Slc4a1) Cl-/HCO3- exchanger mRNAs are induced in kidney. In the colon, epithelial Na+ channel activity is increased and colonic H+,K+-ATPase mRNA is massively induced. These data show that NHE3 is the major absorptive Na+/H+ exchanger in kidney and intestine, and that lack of the exchanger impairs acid-base balance and Na+-fluid volume homeostasis.
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              Carotid baroreceptor stimulation, sympathetic activity, baroreflex function, and blood pressure in hypertensive patients.

              In animals, electric field stimulation of carotid baroreceptors elicits a depressor response through sympathetic inhibition. We tested the hypothesis that the stimulation acutely reduces sympathetic vasomotor tone and blood pressure in patients with drug treatment-resistant arterial hypertension. Furthermore, we tested whether the stimulation impairs the physiological baroreflex regulation. We studied 7 men and 5 women (ages 43 to 69 years) with treatment-resistant arterial hypertension. A bilateral electric baroreflex stimulator at the level of the carotid sinus (Rheos) was implanted > or =1 month before the study. We measured intra-arterial blood pressure, heart rate, muscle sympathetic nerve activity (microneurography), cardiac baroreflex sensitivity (cross-spectral analysis and sequence method), sympathetic baroreflex sensitivity (threshold technique), plasma renin, and norepinephrine concentrations. Measurements were performed under resting conditions, with and without electric baroreflex stimulation, for > or =6 minutes during the same experiment. Intra-arterial blood pressure was 193+/-9/94+/-5 mm Hg on medications. Acute electric baroreflex stimulation decreased systolic blood pressure by 32+/-10 mm Hg (range: +7 to -108 mm Hg; P=0.01). The depressor response was correlated with a muscle sympathetic nerve activity reduction (r(2)=0.42; P<0.05). In responders, muscle sympathetic nerve activity decreased sharply when electric stimulation started. Then, muscle sympathetic nerve activity increased but remained below the baseline level throughout the stimulation period. Heart rate decreased 4.5+/-1.5 bpm with stimulation (P<0.05). Plasma renin concentration decreased 20+/-8% (P<0.05). Electric field stimulation of carotid sinus baroreflex afferents acutely decreased arterial blood pressure in hypertensive patients, without negative effects on physiological baroreflex regulation. The depressor response was mediated through sympathetic inhibition.
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                Author and article information

                Journal
                Front Physiol
                Frontiers in physiology
                Frontiers Media SA
                1664-042X
                1664-042X
                Dec 24 2013
                : 4
                Affiliations
                [1 ] Department of Biomedicine, Aarhus University Aarhus, Denmark.
                Article
                10.3389/fphys.2013.00388
                3870919
                24399970
                38fa031d-7b2c-480e-9038-eb016206b8be
                History

                SLC26,SLC4,SLC9,acidosis,alkalosis,blood pressure,intracellular pH
                SLC26, SLC4, SLC9, acidosis, alkalosis, blood pressure, intracellular pH

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