The release of leukotriene B4 during experimental inflammation

Leukotriene B4 (LTB4) has been detected by radioimmunoassay in inflammatory exudates obtained following the implantation of saline- or carrageenan-soaked polyester sponges in rats. The immunoreactive material was confirmed as LTB4 after extraction and purification by high pressure liquid chromatography. The peak concentration (6.9 +/- 0.5 ng/ml) was detected 6 hr after implantation of sponges soaked in 0.5% carrageenan; thereafter the level declined and was undetectable after 16-24 hr. The concentration of LTB4 during the early phase of the inflammatory response (4-8 hr) is sufficient to induce leukocyte aggregation, chemotaxis and degranulation of polymorphonuclear leukocytes (PMN) in vitro. Therefore, LTB4 may mediate, at least in part, the influx of PMN and contribute to other events which characterise the inflammatory response. The level of thromboxane B2 (TXB2) in the inflammatory exudate followed a similar time-course to that of LTB4 although the maximum concentration was higher (15-30 ng/ml). However, prostaglandin E2 (PGE2) exhibited a different time-course; the maximum level (20-30 ng/ml) was also reached 6-8 hr after implantation but remained elevated at 24 hr. The PMN count in the sponges and the concentrations of both LTB4 and TXB2, but not PGE2, were significantly reduced by prior treatment of the animals with colchicine. This suggests that PMN are the major source of LTB4 and TXB2 in the inflammatory exudate whereas PGE2 is produced in significant amounts by other tissues.