Characterization of an isoform of Na+/K+-ATPase with high affinity for [H-3]ouabain in the rat vas deferens

Abstract

The α and β subunits of Na+/K+-ATPase present distinct isoforms in different tissues and cells.1 The α1 isoform was identified in all cells and is considered the “housekeeping” enzyme. The α2 and α3 isoforms have a more limited distribution. The α3 isoform is located predominantly in neural tissue, whereas the α2 isoform is present in neural tissue, heart ventricles, and adipocytes and is the predominant isoform in adult skeletal muscle. Based on mRNA analysis, the α2 isoform seems to be the main isoform in rat adult smooth muscle as well.1 In smooth muscle of guinea pig vas deferens, there is a specific reduction of the α2 isoform associated with nonspecific postjunctional supersensitivity to various agonists after denervation.2 In the rat vas deferens, a tissue densely innervated by autonomic nervous system and in particular with no, or little, pump contribution to the resting membrane potential,3 the denervation also produces a nonspecific postjunctional supersensitivity,4 but the existence and role of the α2 isoform were not yet demonstrated. Therefore, the present study investigates the presence of the Na+K+-ATPase α2 isoform in the rat vas deferens.