The effects of a 5-lipoxygenase inhibitor, AA-861, on PGI2-like substance production in guinea-pig lungs

To determine the effects of AA-861 on PGI₂ production in guinea-pig lungs, 3 g of guinea-pig lung was chopped in 4 ml of buffer (control group), in buffer with 4 μg/ml indomethacin (indomethacin group) and in buffer with 2.5 × 10⁻⁵M AA-861 (AA-861 group). The chopped lungs were incubated for 30 min. 250 μl of incubation medium from each group was assessed before and after 3, 5, 10, 15, 20, 25 and 30 min of incubation. The incubation medium was centrifuged and the supernatant was tested for a PGI₂-like substance (PGI₂) by platelet aggregation inhibition. PGI₂ was produced mainly during the initial 3–5 min of incubation and was decreased thereafter. PGI₂ production was almost completely inhibited in the indomethacin group at all of the incubation times and was partially inhibited in the AA-861 group during the initial 3–5 minutes. Endogenous 5-lipoxygenase products generated in the early stages of incubation seem to be involved in PGI₂ production in guinea-pig lungs.