Fig. 2.

Inhibition of PI-specific PLC does not block ATP-stimulated ERK activity. In A, primary rat astrocyte cultures were treated with 10 μm U73122 for 30 min before addition of ATP (100 μm, 15 min). ERK activity data (mean ± SEM) were obtained from three experiments, each conducted with duplicate culture plates. ERK activity in untreated cultures was 43.5 ± 8.2 pmol phosphate transferred per minute per milligram of protein. In B, primary rat astrocyte cultures were treated with 10 μm U73122 for 30 min before addition of ATP (500 μm, 30 min), and inositol phosphates were extracted and measured as described in Materials and Methods.