Kidney amiloride-sensitive ENaC are composed of at least three homologous subunits (α, β, γ) located in the apical membranes of collecting tubules. The present study was designed to characterize the developmental changes in the expression of these subunits and to test the hypothesis that glucocorticoids modulate these changes. First, we showed that mRNA levels (expressed in 32P total counts) for each of the three ENaC subunits increased significantly in near-term fetal (F) sheep kidney. After birth, both β and γENaC mRNA levels decreased significantly in newborn (NB) lambs whereas αENaC mRNA remained elevated compared to F. In a second series of studies, a 48 h cortisol (C) infusion (6.2 μmol/h) in 130 d gestation (term 145 d) twin ovine fetuses (n=8 pairs) increased significantly (p<0.05) both αENaC (+197±50%) and βENaC(33±14%), but had no effect on γENaC. These results suggest (a) that the fetal expression of all three ENaC subunits increased near-term, and(b) that cortisol appears to be an important regulator of both α andβENaC in the fetal kidney. Table

Table 1
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