PGD₂ stimulation of cAMP formation in eosinophils via DP receptors.

(A) Purified eosinophils were incubated with PGD₂ (●), BW245C (▪), and PGE₂ (▿) in the presence of rolipram (10 μM) for 15 minutes. Eosinophil cAMP levels were then measured by means of a protein binding assay. The values are means ± SE (n = 4) of determinations on from cells from 4 individuals, each performed in duplicate, and are expressed as percentages of the maximal response (2.25 ± 0.26 pmol cAMP per 10⁶ cells) to PGD₂. Basal levels of cAMP were 0.30 ± 0.15 pmol/10⁶ cells. (B) Human platelets were incubated for 2 minutes at 37°C with PGD₂ (●), BW245C (▪), PGJ₂ (▵), and 13,14-dihydro-15-oxo-PGD₂(○), followed by measurement of cAMP levels. The values are means ± SE of determinations on platelets from 4 individuals and are expressed as percentages of the maximal response to PGD₂, which was 4.95 ± 1.06 pmol cAMP per 3 × 10⁷ platelets, compared with a control value of 0.17 ± 0.05 pmol cAMP per 3 × 10⁷ platelets.