Chapter 15 Catecholamine Regulation of Amiloride-Sensitive Na+ Transport in the Fetal Rat Alveolar Epithelium

Abstract

The chapter presents a study on catecholamine regulation of amiloride-sensitive sodium ion (Na + ) transport in the fetal rat alveolar epithelium. The chapter describes the characteristics of two types of amiloride-sensitive Na + -permeable channels, their roles in the catecholamine-induced Na + absorption, the regulatory mechanisms of these amiloride-sensitive channels, and the switching mechanisms of fetal distal lung epithelial cells (FDLE) from the secretory to the absorptive epithelium. Active Cl – secretion via the fetal lung epithelium, producing the driving force for secretion of the fetal lung fluid essentially plays an important role in development, differentiation, and growth of the fetal lung. On the other hand, this fluid is required to be rapidly reabsorbed as the alveolar cavity is utilized for gas exchange after birth. This reabsorption of the fetal lung fluid is initiated by catecholamine, whose level in blood is increased at birth, via the following pathways. Catecholamine increases the apical Na + conductance via amiloride-sensitive Na + -permeable nonselective cation channels, because of the increases in activity and number of the channel.