Differential regulation of insulin-like growth factor-II receptors in rat hepatocytes and hepatoma cells.
This study compares the regulation of IGF-II receptors in three rat hepatoma lines, HTC, H-35 and 5123tc, and primary rat hepatocytes. In all cell types [125I]IGF-II bound solely to a species of approximately 250 kDa. Cell surface IGF-II receptors in hepatoma cells had slightly lower affinities (1-2 liters/nmol) than in hepatocytes (4 liters/nmol), but slightly higher IGF-I cross-reactivity (2-4% compared to 1% in hepatocytes). In confluent cultures, the three hepatoma lines expressed 5- to 15-fold more cell-surface receptors per cell than hepatocytes. However, while hepatocyte receptors showed marked inverse density-dependence, increasing over 6-fold between dense (3 x 10(5) cells/3.8 cm2) and sparse (0.16 x 10(5) cells/3.8 cm2) cultures, receptors in all hepatoma lines remained at a constant high level regardless of culture density. These distinct regulatory patterns resemble those described for growth-related functions in hepatocytes and hepatoma cells, and are thus consistent with a role for IGF-II receptors in liver cell proliferation.
Scott
C D
CD
Department of Endocrinology, Royal Prince Alfred Hospital, Camperdown, NSW, Australia.
Taylor
J E
JE
Baxter
R C
RC
D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D007335:Insulin-Like Growth Factor II / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008970:Molecular Weight; D051381:Rats; D011972:Receptor, Insulin / Q000302:isolation & purification / Q000378:metabolism*; D017451:Receptors, Somatomedin; D013002:Somatomedins / Q000378:metabolism*
D017451:Receptors, Somatomedin; D013002:Somatomedins; D007335:Insulin-Like Growth Factor II; D011972:Receptor, Insulin