Opposite Effects of Pressurized Steady Versus Pulsatile Perfusion on Vascular Endothelial Cell Cytosolic pH: Role of Tyrosine Kinase and Mitogen-Activated Protein Kinase Signaling

Endothelial cytosolic pH (pHi) modulates ion channel function, vascular tone, and cell proliferation. Steady shear induces rapid acidification in bicarbonate buffer. However, in vivo shear is typically pulsatile, potentially altering this response. We tested effects and mechanisms of pHi modulation by flow pulsatility, comparing pressurized steady versus pulse-flow responses in bovine aortic endothelial cells cultured within glass capillary tubes. Cells were loaded with the fluorescent pHi indicator carboxy seminaphthorhodafluor-1 and perfused with physiological pulsatile pressure and flow generated by a custom servo-control system. Raising mean pressure from 0 to 90 mm Hg at 0.5 mL/min steady flow in bicarbonate buffer induced sustained acidification (−0.33±0.09 pH units, P