ENaC activity is increased in isolated, split-open cortical collecting ducts from protein kinase Cɑ knockout mice.

The epithelial Na channel (ENaC) is negatively regulated by protein kinase C (PKC) as shown using PKC activators in a cell culture model. To determine whether PKCɑ influences ENaC activity in vivo, we examined the regulation of ENaC in renal tubules from PKC^-/- mice. Cortical collecting ducts were dissected and split open, and the exposed principal cells were subjected to cell-attached patch clamp. In the absence of PKCɑ, the open probability (Po) of ENaC was increased three-fold vs. wild-type SV129 mice (0.52 ± 0.04 vs. 0.17 ± 0.02). The number of channels per patch was also increased. Using confocal microscopy, we observed an increase in membrane localization of ɑ-, β-, and y-subunits of ENaC in principal cells in the cortical collecting ducts of PKCɑ^-/- mice compared with wild-type mice. To confirm this increase, one kidney from each animal was perfused with biotin, and membrane protein was pulled down with streptavidin. The nonbiotinylated kidney was used to assess total protein. While total ENaC protein did not change in PKCɑ^-/- mice, membrane localization of all the ENaC subunits was increased. The increase in membrane ENaC could be explained by the observation that ERK1/2 phosphorylation was decreased in the knockout mice. These results imply a reduction in ENaC membrane accumulation and Po by PKCɑ in vivo. The PKC-mediated increase in ENaC activity was associated with an increase in blood pressure in knockout mice fed a high-salt diet. [ABSTRACT FROM AUTHOR]