Cytochalasin B stimulates insulin-like growth factor-binding protein-1 production by Hep G2 cells.
Hep G2 cells were used to study the early sequence of events regulating production of insulin-like growth factor-binding protein-1 (IGFBP-1). Cytochalasin B (100 microM) specifically inhibited 2-deoxyglucose uptake by Hep G2 cells and stimulated IGFBP-1 production 2-fold. Insulin (300 nM) did not stimulate hexose uptake but inhibited IGFBP-1 production more than 50%. A change in IGFBP-1 secretion was observed as early as 2 h after a 15-min or 2-h pulse exposure to either effector. In contrast to IGFBP-1, albumin production was diminished in the presence of cytochalasin B and increased by insulin. From these results we conclude that IGFBP-1 synthesis is (i) stimulated by transient inhibition of cellular glucose uptake and further stimulated by long-term glucose deprivation, and (ii) inhibited by transient exposure to insulin with further inhibition on long-term exposure. These effects are consistent with the dynamic regulation of IGFBP-1 by nutritional status.
Lewitt
M S
MS
Department of Medicine, University of Sydney, New South Wales, Australia.
Baxter
R C
RC
D000418:Albumins / Q000096:biosynthesis; D002352:Carrier Proteins / Q000096:biosynthesis*; D003571:Cytochalasin B / Q000494:pharmacology*; D003572:Cytochalasins / Q000494:pharmacology; D006601:Hexoses / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000502:physiology; D018969:Insulin-Like Growth Factor Binding Proteins; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000378:metabolism; D013002:Somatomedins / Q000096:biosynthesis*; D014407:Tumor Cells, Cultured
D000418:Albumins; D002352:Carrier Proteins; D003572:Cytochalasins; D006601:Hexoses; D007328:Insulin; D018969:Insulin-Like Growth Factor Binding Proteins; D013002:Somatomedins; C007215:cytochalasin E; D003571:Cytochalasin B