Figure 1.

Concentration- and time-dependent effect of PGE₂ on cyclic AMP formation in guinea-pig tracheal epithelial cells. (A) Cells were pre-treated for 15 min with rolipram (10 μM) and incubated in the presence (open circles) or the absence (solid circles) of PGE₂ (1 μM) for 5, 15, 30, 60 and 150 min. The conversion of [³H]-ATP to [³H]-cyclic AMP was assayed as described in Methods. (B) Cells were pre-treated for 15 min with rolipram (10 μM) and then incubated for 15 min with increasing concentrations of PGE₂ (1 nM to 100 μM). The points are the means±s.e.mean of four determinations made with separate cell preparations.