Membrane receptor function and the loss of glucagon-stimulated adenylate cyclase activity in hepatomas.
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| Abstract |
Plasma membranes were prepared from homogenates of two well differentiated hepatomas (Morris rat 7787 and Dalton mouse 9815), two poorly differentiated hepatomas (Morris rat 7288-C and Dalton mouse 129), and normal liver. Adenylate cyclase activity and [125I]iodoglucagon binding were measured in the plasma membrane preparations over a wide range of glucagon concentrations. Nether glucagon-stimulated adenylate cyclase activity nor [125I]iodoglucagon binding could be detected in the poorly differentiated hepatomas. Fluoride and epinephrine stimulated adenylate cyclase activity in all hepatomas. Maximum activity of glucagon-stimulated adenylate cyclase and maximum binding of glucagon in the wall differentiated hepatomas were less than those of normal liver. Plasma membranes from liver and hepatomas were solubilized with Lubrol-PX and, after reducing the concentration of detergent, were incubated with [125I]iodoglucagon and then chromatographed on a column of Bio-Gel A 1,5 m. Two peaks containing both protein and [125I]iodoglucagon were found for normal liver but not for the poorly differentiated hepatomas. Fractions from the Bio-Gel column containing the greatest concentration of protein were also subjected to a binding microassay. Material from the poorly differentiated tumors did not bind glucagon in this system, whereas the solubilized normal liver membranes bound up to 1.4 pmol [125I]iodoglucagon/mg protein. This indicates that there is no detectable glucagon receptor in these undifferentiated tumors.
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| Authors | R D Mirel, H P Morris, R P DiAugustine |
| Journal | Endocrinology (Endocrinology) Vol. 102 Issue 4 Pg. 1237-46 (Apr 1978) ISSN: 0013-7227 [Print] United States |
| PMID | 217618 (Publication Type: Journal Article) |
| Chemical References |
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