Expressions of epithelial Na+ channel subunits in the supraoptic nucleus of the hypothalamus in the male rat in response to dietary NaCl intake

Abstract

All three epithelial Na+ channel (ENaC) subunits (α, β, and γ) were demonstrated in vasopressin (VP) synthesizing magnocellular neurons (MNCs) in the hypothalamic supraoptic (SON) and paraventricular nuclei. Our recent findings showed that ENaC mediates a Na+ leak current that changes the frequency of action potentials in MNCs. In the present study, we assessed the effect of dietary NaCl intake on ENaC subunits in the SON. Male rats were fed either a 8% NaCl diet, a NaCl deficient, or a control diet for two weeks. Then, relative changes in the subunit mRNAs in the SON and kidney were measured by real‐time RT‐PCR. The 8% NaCl diet caused significant increase in β‐ and γ‐ENaC mRNAs in the SON, while expression of α‐ENaC did not change. In contrast, the 8% NaCl diet did not cause any marked changes in expressions of the subunits in the kidney, while a deficiency in dietary NaCl caused a significant rise in α‐ENaC mRNA. Change in the subcellular distribution of α‐ENaC immunoreactivety in MNCs was also observed using confocal microscopy. The labeling in the MNCs from the 8% NaCl diet group was distinctively concentrated towards the plasma membrane in all 5 rats tested, while those from the NaCl deficient and control groups were mainly dispersed in the cytoplasm with no distinct labeling at the plasma membrane. These findings imply that dietary NaCl affects ENaC activity in VP MNCs, which, in turn, affects VP secretion.NIH grant: R21 HL093728