Insulin binding and biological activities in the FRTL-5 rat thyroid cell line.
A cloned rat thyroid cell line (FRTL-5) was examined for both insulin binding and responsiveness. The characteristics of insulin binding to thyroid cells were similar to those observed in typical insulin target cells. The 125I-insulin binding was time and temperature dependent and Scatchard analysis suggested the presence of two major binding sites with high and low affinity constant (Kd = 1.4 X 10(-10) mol/L and 1.5 X 10(-9) mol/L, respectively). 125I-insulin was also internalized and degraded in a temperature-dependent manner. IGF1 was weakly effective in completing 125I-insulin binding to FRTL-5 cells (57% inhibition at 333 nmol/L), whereas noninsulin-related peptide hormones were ineffective. Exposure of FRTL-5 cells to insulin stimulated both methyl-aminoisobutyric acid (M-AIB) and 2-deoxy-D-glucose (2DG) transport. These effects were evident at 10(-9) mol/L and maximal at 10(-7) mol/L insulin. Maximal stimulation was three- to four-fold over basal value for both M-AIB and 2DG transport. These data suggest that insulin specifically binds to FRTL-5 cells and regulates different biological functions of this thyroid cell line.
D000621:Aminoisobutyric Acids / Q000378:metabolism; D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D002999:Clone Cells / Q000378:metabolism; D003847:Deoxyglucose / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D007700:Kinetics; D051381:Rats; D013696:Temperature; D013961:Thyroid Gland / Q000378:metabolism*
D000621:Aminoisobutyric Acids; D007328:Insulin; C017911:2-(methylamino)isobutyric acid; D003847:Deoxyglucose