Induction of glucagon responsiveness in transformed MDCK cells unresponsive to glucagon

Abstract

This chapter discusses a cloned line of Madin–Darby canine kidney (MDCK) cells, which were transformed with Harvey murine sarcoma virus. This line is maintained in continuous culture under the same conditions as the parental MDCK cells in Dulbecco's MEM, 5% fetal bovine serum, 5% CO2/95% air, with 80% humidity. The morphology of this transformed line is more fibroblastic than that of normal cells; in addition, a 21,000 Da protein (p21) coded by the virus has been identified on the inner surface of the plasma membrane of this transformed line. The growth characteristics of transformed MDCK cells are similar to normal cells; both grow equally well in serum free media. Like normal MDCK cells, the adenylate cyclase of the transformed line responds to a variety of hormones. However, transformation results in a selective loss of glucagon responsiveness because of the absence of glucagon binding sites at the cell surface. Thus, this cell line represents a good model system to examine factors that regulate the expression of differentiated functions.