Disruption of the β subunit of the epithelial Na+ channel in mice:: Hyperkalemia and neonatal death associated with a pseudohypoaldosteronism phenotype

The epithelial Na+ channel (ENaC) is composed of three homologous subunits: alpha, beta and gamma. We used gene targeting to disrupt the beta subunit gene of ENaC in mice. The beta ENaC-deficient mice showed normal prenatal development but died within 2 days after birth, most likely of hyperkalemia. In the -/- mice, we found an increased urine Na+ concentration despite hyponatremia and a decreased urine K+ concentration despite hyperkalemia. Moreover, serum aldosterone levels were increased. In contrast to alpha ENaC-deficient mice, which die because of defective lung liquid clearance, neonatal beta ENaC deficient mice did not die of respiratory failure and showed only a small increase in wet lung weight that had little, if any, adverse physiologic consequence. The results indicate that, in vivo, the beta subunit is required for ENaC function in the renal collecting duct, but, in contrast to the alpha subunit, the beta subunit is not required for the transition from a liquid-filled to an air-filled lung. The phenotype of the beta ENaC-deficient mice is similar to that of humans with pseudohypoaldosteronism type 1 and may provide a useful model to study the pathogenesis and treatment of this disorder.