Hepoxilin A3 increases vascular permeability in the rat skin

We have recently shown that hepoxilins are formed by and act on human neutrophils leading to an increase in intracellular levels of calcium and activation of the release of arachidonic acid and diacylglycerol [6, 9]. Since neutrophil activation and accumulation is involved in the inflammatory process resulting in vascular permeability in the rat skin, we investigated the effects of hepoxilins on this process. Hepoxilins administered s.c. resulted in a concentration- and time-dependent leakage of dye to the extravascular compartment of skin from rats to which Evans Blue had been administered. These results were compared to experiments in which prostaglandin E2 was used. The threshold dose of hepoxilin that elicited an effect reached a level of significance over control within 5 min of administration at the 10 ng dose (139% +/- 7%, n = 6). Similar findings were obtained with prostaglandin E2, the level of significance was reached also at 5 min at the 10 ng dose (177% +/- 7% of control, n = 6). The maximum effect observed for both hepoxilin and prostaglandin E2 was 60 min although this did not differ significantly from 30 min except for the highest dose of PGE2 (100 ng). However, the extent of the effect observed for prostaglandin E2 was greater than that for hepoxilin after longer periods, i.e. at 60 min, the prostaglandin E2 effect being 238% +/- 10% of control, and hepoxilin A3 being 167% +/- 10% of control. These results demonstrate that hepoxilins may participate in inflammatory processes.