Expression and developmental regulation of Na+,K+ adenosine triphosphatase in the rat small intestine

Abstract

The Na+,K+-ATPase ion pump plays a critical role in fluid and electrolyte physiology of the small intestine. Here we show that, of the three known α isotypes (αl, α2, and α3) of the sodium pump found in the rat, only al is expressed in the small intestine. The expression of this isotype, considered at the level of mRNA, is under developmental control, with the adult intestine exhibiting approximately a threefold increase in α1 message over the neonate. Cortisone treatment of the neonate results in near-adult levels of al mRNA expression. An increase in the abundance of al isotype parallels the changes in its mRNA expression, β subunit mRNA is expressed coordinately with the al subunit mRNA. A four- to five-fold rise in the Na+, K+-ATPase activity is also developmentally induced.