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 ra t smooth muscle cell line (A(7)r(5)) by functional studies. Our labora tory has used reverse transcriptase (RT)-polymerase chain reaction (PC R) and Northern hybridization techniques to define the type of HKA pre sent in canine whole carotid artery and confluent carotid artery cells . PCR primers to detect an HKA message of unknown isoform were designe d on the basis of homology to known sequences of gastric, colonic, and toad bladder HKA isoforms and dissimilarity to the Na+-K+-adenosinetr iphosphatase isoforms. A PCR product of predicted size was generated f rom cDNAs of both confluent cells and whole vessel carotid artery that possess 91% nucleotide sequence identity to the canine gastric HKA. N orthern hybridization with the PCR product as a probe revealed hybridi zation to whole vessel carotid artery, cultured confluent carotid arte ry cell, kidney, and stomach canine total RNA at the known message siz e 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.