Effect of intracellular pH on vascular tone (35). In the NBCn1 (Slc4a7) knockout mouse (red) vascular endothelial cell (A) and smooth muscle cell (C) pH is reduced (vertical bars show SEM, n = 5 and 6, respectively). This is associated with a reduced endothelial cell mediated smooth muscle cell relaxation to acetylcholine (ACh) of norepinephrine (NE) activated mesenteric small arteries (B) and reduced tension development to NE in the presence of 100 μmol/L nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) E), (vertical bars show SEM, n = 10). In the presence of 10 μmol/L Rho-kinase inhibitor fasudil, the tension development to NE is similar in arteries from wild type and knockout mice (D) (n = 5), consistent with the Rho-kinase being pH sensitive allowing for an effect of intracellular pH on smooth muscle cell tone.