AN INVESTIGATION OF INTRINSIC BUFFERING POWER IN RAT VASCULAR SMOOTH-MUSCLE CELLS

Intrinsic buffering power (beta(i)) has been measured in vascular strips and single cells from rat mesenteric artery. Intracellular pH (pH(i)) regulation was inhibited to prevent overestimation of beta(i) due to acid extrusion or entry via regulatory processes. At resting values of pH(i) (7.0-7.2), a mean value of 41+/-4 mM/pH unit for beta(i) was found. beta(i) increased approximately fivefold from 30 to 150 mM/pH unit over the pH(i) range 7.5-6.5. The mean data relating beta(i) to pH(i) could be described by relating beta(i) to buffer concentrations and pK(a). This gave a value of 310 mM for buffer concentration and a pK(a) of 6.0. As changes in pH(i) are known to have marked effects on vascular tone then the increase in beta(i) as pH(i) falls may be considered as a means of attenuating pH(i) decreases, before pH regulating restores pH(i) to resting levels.