Insulin and growth hormone act synergistically to stimulate insulin-like growth factor-I production by cultured chicken hepatocytes.
Cultured chicken hepatocytes were used to investigate whether insulin and GH interact to regulate insulin-like growth factor-I (IGF-I) production in vitro. In the first set of experiments hepatocytes were preincubated for 6 h in hormone-free medium, and the effects of various combinations of insulin and GH on IGF-I production over the next 24 h were quantified by radioimmunoassay. Basal IGF-I production was 5.36 pg IGF-I/micrograms DNA and this was increased 1.31 +/- 0.13-fold (mean +/- S.E.M.) by insulin, 1.90 +/- 0.24-fold by GH and 4.46 +/- 0.68-fold by a combination of insulin and GH. These results demonstrate that insulin and GH interact synergistically to stimulate IGF-I production in vitro. The synergism with GH occurred at physiological concentrations of insulin with half-maximal stimulation occurring at an insulin concentration of 6 ng/ml. In hepatocytes which had been exposed to insulin immediately before the start of the experiment, the presence of insulin was no longer required for maximal stimulation of IGF-I production by GH. This in-vitro system will facilitate the study of the molecular basis of the interaction between insulin and GH.
Houston
B
B
Department of Cellular and Molecular Biology, AFRC Institute of Animal Physiology and Genetics Research, Roslin, Midlothian.
O'Neill
I E
IE
D000818:Animals; D002478:Cells, Cultured; D002645:Chickens; D004357:Drug Synergism; D013006:Growth Hormone / Q000378:metabolism* / Q000494:pharmacology; D007328:Insulin / Q000378:metabolism* / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism*; D008297:Male
D007328:Insulin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone