Glucagon and Epinephrine Activation of Adenylate Cyclase and Clucagon Binding in Morris Hepatomas

Glucagon and epinephrine-activatcd adenylate cyclase in participate preparations from a well-differentiated (9121) and a highly undifferentiated (3924A) Morris hepatoma was compared to normal liver. Although maximal increases in enzyme activity in response to glucagon were approximately 2-fold greater in the normal liver, half-maximal enzyme activation occurred at virtually identical cona.itrat:ons in normal and neoplastic liver. Thus, the present investigation does not support a previous report of hormone unresponsive adenylate cyclase in highly undifferentiated Morris hepatomas. In addition, the binding of ¹²⁵ I-glucagon to washed membrane particles was similar in the hepatomas as compared to the normal. We conclude, therefore, that if there is a defect in the adenylate cyclase system, it is distal to the membrane-bound enzyme. (Endocrinology94: 279, 1974)