Figure 2. Extracellular acidity triggers Ca²⁺ mobilization in HT29 cells in Ca²⁺-containing solutions.

A: Normal physiological salt solutions with varying pH values (6.0–4.0) adjusted by HCl triggered a rise in [Ca²⁺]_cyt that was peaked at pH 5.0, then gradually returned to the baseline levels even with additional extracellular acidosis. B: Summarized data showing that extracellular acidosis caused a pH (6.0–5.0)-dependent rise in net peak of [Ca²⁺]_cyt with a pH_0.5 of approximate 5.9. Values are mean ± SE, n = 52 cells for each tracing or bar. **P < 0.01 vs. pH 7.4.