Different molecular mechanisms are involved in the multihormonal control of glucose transport in FRTL5 rat thyroid cells.
We investigated the molecular mechanisms by which TSH, insulin and IGF-1 modulate the glucose transport system in FRTL5 cells. We found that TSH, insulin and IGF-1 increased the glucose transporter Glut-1 specific mRNA levels 6, 8 and 5 fold over control, respectively. The effect on Glut-1 mRNA was evident after 2 hours, followed by an increased Glut-1 protein expression in whole cells, as judged by western blot analysis, after 5 hours of stimulation with all the hormones studied. In contrast, plasma membrane Glut-1 increased (300-400% over control) after 2 hours of stimulation with TSH (10 mU/ml), dibutyryl-cAMP (1mM), IGF-1 (10 ng/ml) and insulin (10 nM). These data indicate that the glucose transport system is under multihormonal control in FRTL5 cells. Two different mechanisms are involved in TSH, IGF-1 and insulin stimulation of the glucose transport: a) neosynthesis of Glut-1 by activation of gene expression; b) recruitment of carriers from the intracellular pool to the plasma membrane.
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Dipartimento di Medicina Clinica e Sperimentale, Cattedra di Endocrinologia, University of Reggio Calabria, Catanzaro, Italy.
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D000818:Animals; D002460:Cell Line; D005947:Glucose / Q000378:metabolism*; D051272:Glucose Transporter Type 1; D007328:Insulin / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D013961:Thyroid Gland / Q000378:metabolism*; D013972:Thyrotropin / Q000494:pharmacology*
D051272:Glucose Transporter Type 1; D007328:Insulin; D009004:Monosaccharide Transport Proteins; D012333:RNA, Messenger; C495679:Slc2a1 protein, rat; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D005947:Glucose