Molecular evidence for a vascular smooth muscle H+-K+-ATPase.

Evidence for an H+-K+-adenosinetriphosphatase (HKA) in vascular smooth muscle cells has recently been demonstrated in the rat aorta and a rat smooth muscle cell line (A(7)r(5)) by functional studies. Our laboratory has used reverse transcriptase (RT)-polymerase chain reaction (PCR) and Northern hybridization techniques to define the type of HKA present in canine whole carotid artery and confluent carotid artery cells. PCR primers to detect an HKA message of unknown isoform were designed on the basis of homology to known sequences of gastric, colonic, and toad bladder HKA isoforms and dissimilarity to the Na+-K+-adenosinetriphosphatase isoforms. A PCR product of predicted size was generated from cDNAs of both confluent cells and whole vessel carotid artery that possess 91% nucleotide sequence identity to the canine gastric HKA. Northern hybridization with the PCR product as a probe revealed hybridization to whole vessel carotid artery, cultured confluent carotid artery cell, kidney, and stomach canine total RNA at the known message size for the gastric HKA isoform. These data suggest that vascular smooth muscle cells express an HKA mRNA that may be identical to the gastric isoform.