Myogenic vasoconstriction in mouse renal interlobar arteries:: role of endogenous β and γENaC

Mechanosensitive ion channels are thought to initiate pressure-induced vasoconstriction, however, the molecular identity of these channels is unknown. Recent work from our laboratory suggests that members of the Degenerin/Epithelial Na+ Channel (DEG/ENaC) family may be components of the mechanosensitive ion channel complex in vascular smooth muscle (VSM); however, the specific DEG/ENaC proteins mediating myogenic constriction are unknown. The goal of this study is to determine if specific knockdown of beta or gamma ENaC, using dominant-negative (DN) or small-interference RNA (siRNA) molecules, inhibits pressure-induced vasoconstriction in mouse renal interlobar arteries. To address this goal, isolated arteries were transiently transfected with beta or gamma ENaC DN-cDNA or siRNA molecules. After 24 h, vessels were either 1) cannulated and pressurized for pressure-diameter response curves or 2) dissociated and immunolabeled to determine VSM cell endogenous ENaC protein expression. We found that transfection of beta ENaC DN-cDNA or siRNA suppresses beta-, but not gamma ENaC protein expression. Similarly, gamma ENaC DN-cDNA or siRNA suppresses gamma-, but not beta ENaC protein expression. In addition, transfection of beta- or gamma ENaC DN-cDNA or siRNA molecules inhibits pressure-induced vasoconstriction, but does not block agonist-induced vasoconstriction. Our results provide the first direct evidence that beta and gamma ENaC proteins are essential in mediating myogenic vasoconstriction in mouse renal interlobar arteries.