5-lipoxygenase metabolites of arachidonic acid regulate volume decrease by mudpuppy red blood cells

We examined whether metabolites of arachidonic acid (AA) regulate K+ efflux during regulatory volume decrease (RVD) by mudpuppy red blood cells (RBCs). Volume regulation was inhibited by the phospholipase A(2) antagonists mepacrine (10 mu M) and ONO-RS-082 (10 mu M); the inhibitory effect of ONO-RS-082 was reversed by gramicidin (5 mu M). Eicosatetraynoic acid (ETYA, 100 mu M), a general antagonist of AA metabolism, also blocked RVD. In addition, volume regulation was inhibited by the lipoxygenase pathway antagonist nordihydroguaiaretic acid (NDGA, 10 mu M), the 5 lipoxygenase antagonists AA-861 (5 mu M) and curcumin (20 mu M), and by the 5-lipoxygenase activating protein inhibitor L-655,298 (5 mu M). Inhibition by all four of these agents was reversed with gramicidin. In contrast, the 12- and 15-lipoxygenase pathway inhibitor ethyl-3,4-dihydroxy-benzylidene-cyanoacetate (EDBCA, 1 mu M) and the cytochrome P-450 monooxygenase pathway blocker ketoconazole (20 mu M) had no effect. On the other hand, the cyclooxygenase pathway inhibitor aspirin (100 mu M) slightly enhanced RVD. Consistent with these findings, a K+-selective whole cell conductance responsible for K+ efflux during cell swelling was inhibited by ONO-RS-082 (10 mu M), NDGA (10 mu M), AA-861 (5 mu M), curcumin (20 mu M), and L-655,298 (5 mu M). In contrast, EDBCA (1 mu M), ketoconazole (20 mu M), and indomethacin (10 mu M) did not block this whole cell conductance. These results indicate that a channel mediating K+ loss during RVD is regulated by a 5-lipoxygenase metabolite of arachidonic acid.