Identification and immunolocalization of ecto-ATPDase in chicken stomach

The distribution of the extracellular adenosine tri- and di-phosphatase (ecto-ATPDase) in adult chicken tissues was investigated using a monoclonal antibody (MC18) generated previously from chicken oviduct. Ecto-ATPDase was determined to be most abundant in stomach by Western blot analysis of crude tissue homogenates. The ecto-ATPDase activity from solubilized stomach microsomes and a purified oviduct control was depleted 64% and 72%, respectively, by immunoprecipitation with MC18. Both oviduct and stomach ecto-ATPDases had an M(r) of approximately 80 kDa based on SDS-PAGE analysis. In addition, the enzymology of the ecto-ATPDase from both tissues was very similar. It is concluded that the same ecto-ATPDase is present in stomach and oviduct. Furthermore, immunolocalization of the stomach ecto-ATPDase with MC18 showed the enzyme to be localized in the apical membranes of the oxyntico-peptic cells, suggesting a role for the ecto-ATPDase in secretion.