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 (pHi) regulation was inhibited to prevent overestimation of beta i due to acid extrusion or entry via regulatory processes. At resting values of pHi (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 pHi range 7.5-6.5. The mean data relating beta i to pHi could be described by relating beta i to buffer concentrations and pKa. This gave a value of 310 mM for buffer concentration and a pKa of 6.0. As changes in pHi are known to have marked effects on vascular tone then the increase in beta i as pHi falls may be considered as a means of attenuating pHi decreases, before pH regulation restores pHi to resting levels.