Reversibility (homologous) and persistency (heterologous) of the desensitizations of the intracellular calcium response to LPA.

<p>Cells overexpressing LPA₁ (panel A, black symbols and lines), LPA₂ (panel B, blue symbols and lines) or LPA₃ (panel C, red symbols and lines) receptors were preincubated in the presence of 1 μM PMA for 2 min (open symbols, dotted lines) or with 1 μM LPA for 10 minutes and then extensively washed. Incubation was continued for the times indicated and cells were challenged with 1 μM LPA and the increase in intracellular free calcium concentration was determined. Plotted are the increases in calcium as the percentage of that obtained in cells preincubated without any agent (control, time 0) as mean ± S. E. M. of 5–6 experiments using different cell preparations.