Hepoxilin A, hydroxyepoxide metabolite of arachidonic acid, stimulates transport of 45Ca across the guinea pig visceral yolk sac

The effect of hepoxilin A, a newly isolated hydroxyepoxide metabolite of arachidonic acid, on calcium transport across the visceral yolk sac membrane of the guinea pig was investigated in vitro in Ussing chambers. While 1-14C-labelled hepoxilin A itself was not transported across the membrane, it increased the rate of transport of calcium toward the side to which hepoxilin A was added. The degree of increase in calcium transport was similar whether hepoxilin A was added to the maternal side or to the fetal side of the membrane. The observed effect was dependent on the concentration of hepoxilin A over a narrow range (0.5–1.0 × 10−6 M). It was also dependent on the time of incubation reaching maximal effect by 25 min. We have recently observed that hepoxilin A is formed from platelet-derived 12-hydroperoxyeicosatetraenoic acid (12-HPETE) through hernin and hemoglobin catalysis as well as during perifusion of 12-HPETE through isolated pancreatic islets. The present study suggests that hepoxilin A, if formed in vivo, could play a role in the mobilization of calcium.