title: The effect of extracellular pH changes on intracellular pH and nitric oxide concentration in endothelial and smooth muscle cells from rat aorta.
abstract: OBJECTIVE
  It has been known for more than a century that pH changes can alter vascular tone. However, there is no consensus about the effects of pH changes on vascular response. In this study, we investigated the effects of extracellular pH (pHo) changes on intracellular pH (pHi) and intracellular nitric oxide concentration ([NO]i) in freshly isolated endothelial cells and cross sections from rat aorta.
  
  
  METHODS
  The HCl was used to reduce the pHo from 7.4 to 7.0 and from 7.4 to 6.5; the NaOH was used to increase the pHo from 7.4 to 8.0 and from 7.4 to 8.5. The fluorescent dyes 5-(and-6)-carboxy SNARF-1, acetoxymethyl ester, acetate (SNARF-1) and diaminofluorescein-FM diacetate (DAF-FM DA) were employed to measure the pHi and [NO]i, respectively. The fluorescence intensity was measured in freshly isolated endothelial cells by flow cytometry and in freshly obtained aorta cross sections by confocal microscopy.
  
  
  RESULTS
  The endothelial and vascular smooth muscle pHi was increased at pHo 8.5. The extracellular acidification did not change the endothelial pHi, but the smooth muscle pHi was reduced at pHo 7.0. At pHo 8.5 and pHo 6.5, the endothelial [NO]i was increased. Both extracellular alkalinization and acidification increased the vascular smooth muscle [NO]i.
  
  
  CONCLUSIONS
  Not all changes in pHo did result in pHi changes, but disruption of acid-base balance in both directions induced NO synthesis in the endothelium and/or vascular smooth muscle.
authors.affiliation: Laboratory of Endothelial Function, Department of Surgery and Anatomy, School of Medicine, University of São Paulo, Ribeirão Preto, SP, Brazil.
authors.forename: Verena K
authors.initials: VK
authors.lastname: Capellini
authors.forename: Carolina B A
authors.initials: CB
authors.lastname: Restini
authors.forename: Lusiane M
authors.initials: LM
authors.lastname: Bendhack
authors.forename: Paulo R B
authors.initials: PR
authors.lastname: Evora
authors.forename: Andréa C
authors.initials: AC
authors.lastname: Celotto
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001011:Aorta / Q000166:cytology*; D001578:Benzopyrans / Q000378:metabolism; D042783:Endothelial Cells / Q000737:chemistry* / Q000378:metabolism; D005434:Flow Cytometry; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D018613:Microscopy, Confocal; D032389:Myocytes, Smooth Muscle / Q000737:chemistry* / Q000378:metabolism; D009284:Naphthols / Q000378:metabolism; D009569:Nitric Oxide / Q000378:metabolism*; D051381:Rats; D012235:Rhodamines / Q000378:metabolism
chemical_list: D001578:Benzopyrans; D009284:Naphthols; D012235:Rhodamines; C091666:seminaphthorhodaminefluoride; D009569:Nitric Oxide