Background-Disturbances in pH affect artery function, but the mechanistic background remains controversial. We investigated whether Na ϩ ,HCO 3 Ϫ cotransporter NBCn1, by regulating intracellular pH (pH i ), influences artery function and blood pressure regulation. Methods and Results-Knockout of NBCn1 in mice eliminated Na ϩ ,HCO 3 Ϫ cotransport and caused a lower steady-state pH i in mesenteric artery smooth muscle and endothelial cells in situ evaluated by fluorescence microscopy. Using myography, arteries from NBCn1 knockout mice showed reduced acetylcholine-induced NO-mediated relaxations and lower rho-kinase-dependent norepinephrine-stimulated smooth muscle Ca 2ϩ sensitivity. Acetylcholine-stimulated NO levels (electrode measurements) and N-nitro-L-arginine methyl ester-sensitive L-arginine conversion (radioisotope measurements) were reduced in arteries from NBCn1 knockout mice, whereas relaxation to NO-donor S-nitroso-Nacetylpenicillamine, acetylcholine-induced endothelial Ca 2ϩ responses (fluorescence microscopy), and total and Ser-1177 phosphorylated endothelial NO-synthase expression (Western blot analyses) were unaffected. Reduced NO-mediated relaxations in arteries from NBCn1 knockout mice were not rescued by superoxide scavenging. Phosphorylation of myosin phosphatase targeting subunit at Thr-850 was reduced in arteries from NBCn1 knockout mice. Evaluated by an in vitro assay, rho-kinase activity was reduced at low pH. Without CO 2 /HCO 3 Ϫ , no differences in pH i , contraction or relaxation were observed between arteries from NBCn1 knockout and wild-type mice. Based on radiotelemetry and tail-cuff measurements, NBCn1 knockout mice were mildly hypertensive at rest, displayed attenuated blood pressure responses to NO-synthase and rho-kinase inhibition and were resistant to developing hypertension during angiotensin-II infusion. Conclusions-Intracellular acidification of smooth muscle and endothelial cells after knockout of NBCn1 inhibits NO-mediated and rho-kinase-dependent signaling in isolated arteries and perturbs blood pressure regulation. (Circulation. 2011;124:1819-1829.)Key Words: pH Ⅲ hypertension Ⅲ blood pressure Ⅲ nitric oxide Ⅲ rho-kinase B lood pressure dysregulation is a major cause of human disease. Hypertension is a risk factor for development of coronary heart disease, stroke, and peripheral vascular disease 1-3 whereas hypotension is related to syncope and falls. 4,5 Both hyper-and hypotension increase overall mortality. 6 -8 Editorial see p 1806 Clinical Perspective on p 1829Arterial tone regulation is important for blood pressure control and is modulated by local and systemic factors. Sustained changes in intracellular pH (pH i ) of vascular smooth muscle cells (VSMCs) and endothelial cells (ECs) occur physiologically and pathologically, but have been difficult to investigate experimentally, and little is known about their vascular effects. 9 It has, however, been proposed that endothelial enzymes (eg, endothelial nitric oxide synthase [eNOS] 10 and endothelin converting...

BACKGROUND AND PURPOSEHypoxia causes vasodilatation of coronary arteries, but the underlying mechanisms are poorly understood. We hypothesized that hypoxia reduces intracellular Ca 2+ concentration ([Ca 2+ ]i) by opening of K channels and release of H2S. EXPERIMENTAL APPROACHPorcine coronary arteries without endothelium were mounted for measurement of isometric tension and [Ca 2+ ]i, and the expression of voltage-gated K channels KV7 channels (encoded by KCNQ genes) and large-conductance calcium-activated K channels (KCa1.1) was examined. Voltage clamp assessed the role of KV7 channels in hypoxia. KEY RESULTSGradual reduction of oxygen concentration from 95 to 1% dilated the precontracted coronary arteries and this was associated with reduced [Ca 2+

BACKGROUND AND PURPOSEThe intermediate conductance calcium/calmodulin-regulated K + channel KCa3.1 produces hyperpolarizing K + currents that counteract depolarizing currents carried by transient receptor potential (TRP) channels, and provide the electrochemical driving force for Cl − and fluid movements. We investigated whether a deficiency in KCa3.1 (KCa3.1) protects against fatal pulmonary circulatory collapse in mice after pharmacological activation of the calcium-permeable TRP subfamily vanilloid type 4 (TRPV4) channels. EXPERIMENTAL APPROACHAn opener of TRPV4 channels, GSK1016790A, was infused in wild-type (wt) and KCa3.1 −/− mice; haemodynamic parameters, histology and pulmonary vascular reactivity were measured; and patch clamp was performed on pulmonary arterial endothelial cells (PAEC). KEY RESULTSIn wt mice, GSK1016790A decreased right ventricular and systemic pressure leading to a fatal circulatory collapse that was accompanied by increased protein permeability, lung haemorrhage and fluid extravasation. In contrast, KCa3.1 −/− mice exhibited a significantly smaller drop in pressure to GSK1016790A infusion, no haemorrhage and fluid water extravasation, and the mice survived. Moreover, the GSK1016790A-induced relaxation of pulmonary arteries of KCa3.1 −/− mice was significantly less than that of wt mice. GSK1016790A induced TRPV4 currents in PAEC from wt and KCa3.1 −/− mice, which co-activated KCa3.1 and disrupted membrane resistance in wt PAEC, but not in KCa3.1 −/− PAEC. CONCLUSIONS AND IMPLICATIONSOur findings show that a genetic deficiency of KCa3.1 channels prevented fatal pulmonary circulatory collapse and reduced lung damage caused by pharmacological activation of calcium-permeable TRPV4 channels. Therefore, inhibition of KCa3.1channels may have therapeutic potential in conditions characterized by abnormal high endothelial calcium signalling, barrier disruption, lung oedema and pulmonary circulatory collapse.

BackgroundPulmonary alveolar microlithiasis (PAM) is caused by genetic variants in the SLC34A2 gene, which encodes the sodium-dependent phosphate transport protein 2B (NaPi-2b). PAM is characterised by deposition of calcium phosphate concretions (microliths) in the alveoli leading to pulmonary dysfunction. The variant spectrum of SLC34A2 has not been well investigated and it is not yet known whether a genotype–phenotype correlation exists.MethodsWe collected DNA from 14 patients with PAM and four relatives, and analysed the coding regions of SLC34A2 by direct DNA sequencing. To determine the phenotype characteristics, clinical data were collected and a severity score was created for each variant, based on type and localisation within the protein.ResultsWe identified eight novel allelic variants of SLC34A2 in 14 patients with PAM. Four of these were nonsense variants, three were missense and one was a splice site variant. One patient was heterozygous for two different variants and all other patients were homozygous. Four patients were asymptomatic and 10 patients were symptomatic. The severity of the disease was associated with the variant severity.ConclusionsOur findings support a significant role for SLC34A2 in PAM and expand the variant spectrum of the disease. Thus, SLC34A2 variants were detected in all patients and eight novel allelic variants were discovered. An association between disease severity and the severity of the variants was found; however, this needs to be investigated in larger patient populations.

These novel PDE1 inhibitors induce vasodilation and lower BP, suggesting a potential use of these vasodilators in the treatment of hypertension and vasospasm.