RT-PCR detection of Na,K-ATPase subunit isoforms in human umbilical vein endothelial cells (HUVEC): Evidence for the presence of alpha 1 and beta 3

The endothelial Na,K-ATPase is an active component in maintaining a variety of normal vascular functions. The enzyme is characterized by a complex mol ecular heterogeneity that results from differential expression and associat ion of multiple isoforms of both its alpha- and beta -subunits. The aim of the present study was to determine which isoforms of the Na,K-ATPase are ex pressed in human endothelial cells. HUVEC (human umbilical vein endothelial cells) were used as a model of well known human endothelial cells. The hig h sensitive method RT-PCR was used with primers specific for the various is oforms of the alpha- and beta -subunits of the Na,K-ATPase. The results sho w that HUVEC express alpha1-, but not alpha2-, alpha3- or alpha4-isoforms o f the catalytic subunit and that beta3- but not beta2- or beta1-isoforms is present in these cells. These findings are in contradiction with our previ ous detection of Na,K-ATPase isoforms in HUVEC using antibodies (14). Such results raise the technical problem of the specificity of the available ant ibodies directed against the different isoforms as well as the question of the physiological relevance of the diversity of the Na,K-ATPase isoforms.