The rat liver ecto-ATPase/C-CAM cDNA detects induction of carcinoembryonic antigen but not the mercurial-insensitive ecto-ATPase in human hepatoma Li-7A cells treated by epidermal growth factor and cholera toxin.

The rat liver ectoATPase has reportedly been cloned. The cDNA, a member of the carcinoembryonic antigen (CEA) gene family, was shown to increase aggregation of transfected cells, but ATPase activity was not evaluated. Using this cDNA as a probe to clone the mercurial-insensitive ectoATPase (MI-ectoATPase) of human hepatoma Li-7A cells, the cDNA obtained was that of CEA which has no ATPase activity. The probe also did not detect increased transcription when MI-ectoATPase activity was induced in Li-7A cells. It is concluded that the "rat liver ectoATPase cDNA" codes for a cell adhesion molecule but does not code for an ectoATPase. It was also discovered that expression of four CEA transcripts in Li-7A cells was markedly stimulated by a single growth modulator, EGF, and was further stimulated by a cAMP elevating agent, cholera toxin.