Measurement of intracellular pH in isolated bovine articular chondrocytes

Cartilage is an avascular tissue, the cells of which are exposed to reduced extracellular pH. The synthesis of cartilage matrix by chondrocytes is pH-sensitive and therefore control of intracellular pH (pHi) is important. We have measured the pHi of chondrocytes in MOPS-buffered saline (pH 7.4) using the fluorescent dye 2',7'-bis-2-(carboxyethyl)-5(6)-carboxyfluorescein. Mean pHi was 7.10 +/- 0.04 (+/- S.E.M., n = 22), and intracellular buffering power was 30 +/- 4 mmol l-1 (pH unit)-1 when pHi was displaced over the range 7.4-7.8 (n = 13). Recovery from acid load was blocked by 100 microM-ethylisopropylamiloride or by removal of extracellular Na+, indicating that these cells possess the Na(+)-H+ antiporter.