Figure 1.

Integrin- and LPA-induced increases in pH_i are regulated primarily by NHE1 activity. (A) Intracellular pH recoveries from an NH₄Cl-induced acid load were determined in a nominally HCO₃⁻-free HEPES buffer. The rates of pH_i recoveries (dpH_i/dt) were measured at intervals of 0.05 pH units. (B) Quiescent pH_i and pH_i induced by integrin activation and LPA were determined in cells maintained in SFM for 18–24 h and then replated on poly-l-lysine–coated coverslips in a HCO₃-containing buffer. Integrin activation was induced by cross-linking antibodies to α5β1 integrins as described in MATERIALS AND METHODS. LPA effects on pH_i were determined by treating quiescent cells with 0.5 μM LPA for 10 min. Data are expressed as the mean ± SEM of three to four separate cell preparations.