Rapid Actions of Steroids. Focus on “Nongenomic Regulation of ENaC by Aldosterone”

Steroid hormones act throughout the body altering many cellular functions. The most well-known responses involve a genomic signaling pathway that results in production of new proteins. A mounting number of examples have been elucidated showing that steroid hormones also can produce responses by nongenomic means. Unlike the more extensively studied cytoplasmic steroid receptors, membrane receptors for steroids initiate signaling cascades that alter function in as little as a few seconds. Aldosterone is a steroid hormone with dramatic influence on Na ⁺ absorption across epithelia, particularly in renal collecting ducts. Activation of apical membrane Na ⁺ channels is a key event in the genomic signaling pathway for stimulating Na ⁺ absorption. In the current article in focus, Zhou and Bubien present evidence for rapid aldosterone activation of amiloride-sensitive epithelial Na ⁺ channels (ENaC) by a nongenomic signaling pathway. Thus, the epithelial response to aldosterone not only involves the large number of newly synthesized proteins but also can include rapid activation of Na ⁺ channels, leading to higher rates of electrogenic Na ⁺ absorption.