LPA stimulation of ⁴⁵Ca⁺⁺entry into fresh human erythrocytes as a function of time.

RBCs were washed, loaded with Quin-2 (a Ca⁺⁺ chelator), and suspended in HEPES buffer containing tracer amounts of⁴⁵Ca⁺⁺. After a 30-minute equilibration, RBCs were stimulated with 5 μmol/L LPA (open squares) or buffer alone (closed squares). At the desired times after stimulation, the cells were washed and assayed for hemoglobin content and radioactivity, as described in “Materials and methods.” The data points represent the mean ± SD, where n = 6.