Effects of lipids on ENaC activity in cultured mouse cortical collecting duct cells.
Direct effects on epithelial Na+ channels (ENaC) activity by lipids, e.g., arachidonic acid (AA), eicosatetraynoic acid (ETYA), linoleic acid (LA), stearic acid (SA), hydroxyeicosatetraenoic acid (HETE), 11,12-epoxyeicosatrienoic acid (EET), (PGF2), and (PGE2), in cultured mouse cortical collecting duct (M1) cells were clarified by using single-channel recordings in this study. In a cell-attached recording, a bath application of 10 microM AA significantly reduced the ENaC open probability (NPo), whereas 10 microM ETYA or 5 microM LA only induced a slight inhibition. The inside-out recording as a standard protocol was thereafter performed to examine effects of these lipids on ENaC activity. Within 10 min after the formation of the inside-out configuration, the NPo of ENaC in cultured mouse cortical collecting duct (M1) cells remained relatively constant. Application of ETYA or LA or SA exhibited a similar inhibition on the channel NPo when applied to the extracellular side, suggesting that fatty acids could exert a nonspecific inhibition on ENaC activity. 11,12-EET, a metabolite of AA via the cytochrome P450 epoxygenase pathway, significantly inhibited the ENaC NPo, whereas 20-HETE, a metabolite of AA via the hydroxylase pathway, only caused a small inhibition of the ENaC NPo, to a similar degree as that seen with ETYA and LA. However, both PGE2 and PGF2alpha significantly enhanced the ENaC NPo. These results suggest that fatty acids exert a nonspecific effect on ENaC activity due to the interaction between the channel proximity and the lipid. The opposite effects of 11,12-EET and prostaglandin (PG) implicate different mechanisms in regulation of ENaC activity by activation of epoxygenase and cyclooxygenase.
Wang
Su
S
Department of Physiology, University of Birmingham, Edgbaston, B15 2TT, UK.
Meng
Fei
F
Xu
Jingyuan
J
Gu
Yuchun
Y
D000818:Animals; D002478:Cells, Cultured; D053503:Epithelial Sodium Channels / Q000502:physiology*; D005227:Fatty Acids / Q000494:pharmacology / Q000502:physiology*; D015640:Ion Channel Gating; D007672:Kidney Cortex / Q000166:cytology; D007685:Kidney Tubules, Collecting / Q000166:cytology; D051379:Mice; D018408:Patch-Clamp Techniques; D011453:Prostaglandins / Q000502:physiology*
D053503:Epithelial Sodium Channels; D005227:Fatty Acids; D011453:Prostaglandins