Epoxyeicosatrienoic acid metabolites inhibit Kir4.1/Kir5.1 in the distal convoluted tubule

Cytochrome P -450 (Cyp) epoxygenase-dependent metabolites of arachidonic acid (AA) have been shown to inhibit renal Na + transport, and inhibition of Cyp-epoxygenase is associated with salt-sensitive hypertension. We used the patch-clamp technique to examine whether Cyp-epoxygenase-dependent AA metabolites inhibited the basolateral 40-pS K + channel (Kir4.1/Kir5.1) in the distal convoluted tubule (DCT). Application of AA inhibited the basolateral 40-pS K + channel in the DCT. The inhibitory effect of AA on the 40-pS K + channel was specific because neither linoleic nor oleic acid was able to mimic the effect of AA on the K + channel. Inhibition of Cyp-monooxygenase with N -methylsulfonyl-12,12-dibromododec-11-enamide or inhibition of cyclooxygenase with indomethacin failed to abolish the inhibitory effect of AA on the 40-pS K + channel. However, the inhibition of Cyp-epoxygenase with N -methylsulfonyl-6-(propargyloxyphenyl)hexanamide abolished the effect of AA on the 40-pS K + channel in the DCT. Moreover, addition of either 11,12-epoxyeicosatrienoic acid (EET) or 14,15-EET also inhibited the 40-pS K + channel in the DCT. Whole cell recording demonstrated that application of AA decreased, whereas N -methylsulfonyl-6-(propargyloxyphenyl)hexanamide treatment increased, Ba 2+ -sensitive K + currents in the DCT. Finally, application of 14,15-EET but not AA was able to inhibit the basolateral 40-pS K + channel in the DCT of Cyp2c44 -/- mice. We conclude that Cyp-epoxygenase-dependent AA metabolites inhibit the basolateral Kir4.1/Kir5.1 in the DCT and that Cyp2c44-epoxygenase plays a role in the regulation of the basolateral K + channel in the mouse DCT.