PURIFICATION AND IMMUNOHISTOCHEMICAL LOCALIZATION OF THE ATP-DIPHOSPHOHYDROLASE IN BOVINE LUNGS

We have recently described different isoforms of mammalian ATP diphosp hohydrolase (ATPDase; EC 3.6.1.5). In the present study, we purified t he lung ATPDase by column chromatographies followed by polyacrylamide gel electrophoresis under nondenaturing conditions. The active polypep tide that has a molecular mass of 78 kDa was identified by affinity la beling to the ATP analog 5'-p-fluorosulfonylbenzoyladenosine (FSBA), f ollowed by detection on Western blot with an antibody specific for FSB A. N-glycosidase F treatment shifted the molecular mass of the 78-kDa polypeptide down to 54 kDa, indicating that the enzyme bears similar t o 6-12 NH2-linked oligosaccharide chains. A polyclonal antibody raised against the pancreas ATPDase, which specifically recognized the 78-kD a glycoprotein on Western blot, was used to carry out an immunological survey of the enzyme distribution in bovine lungs. Immunoreactivity w as detected on airway epithelia from the trachea down to alveolar cell s, airway and vascular smooth muscle cells, submucous glands, chondroc ytes, leucocytes, as well as endothelial and mesothelial cells. Such a nide distribution suggests that the ATPDase may affect a variety of p hysiological effects mediated by extracellular nucleotides, such as ai rway smooth muscle tone, surfactant secretion, platelet aggregation, a nd inflammation.