Release of eicosanoids in rat peritoneal cavity during the Arthus reaction. Effect of the PAF-antagonist BN-52021 and indomethacin.

An Arthus reaction was induced in the rat peritoneal cavity. The inflammatory exudates were collected 10 min after induction of the reaction and analysed for the presence of prostaglandin E2 (PGE2) and thromboxane B2 (TXB2) by enzyme immunoassays (EIA), and of leukotriene B4 (LTB4) by radioimmunoassay. Our results showed that control release (CONT) of eicosanoids in the peritoneal cavity averaged 2.3 ng/ml for TXB2, 0.21 ng/ml for PGE2 and 18 pg/ml for LTB4. Following antigen challenge, the levels of TXB2, PGE2 and LTB4 in the peritoneal cavity increased to 17.0 ng/ml, 0.41 ng/ml and 49.0 pg/ml, respectively. Indomethacin totally inhibited the release of PGE2 and TXB2 whereas it increased by 326% the release of LTB4. The PAF antagonist, BN-52021 significantly inhibited (around 40%) the release of LTB4 in rat peritoneal cavity, increased the release of PGE2, and did not affect the release of TXB2. These results clearly suggest a mediatory role for both cyclooxygenase and lipoxygenase products in Arthus reaction and provide evidence that PAF is also involved in complex interactions with the eicosanoids.