Glucose transport stimulation by thyroid hormone in ARL 15 cells: partial role of increased GLUT1 glucose transporter gene transcription.

We have previously reported that the stimulation of glucose transport by thyroid hormone in the rat liver-derived ARL 15 cell line is attributable, at least in part, to increased abundance of cellular glucose transporters with a corresponding increase in the mRNA coding for the GLUT1 glucose transporter isoform. To elucidate further the mechanism by which thyroid hormone increases glucose transport, we examined the time-course of the effect of L-triiodothyronine (T3) on 3H-2-deoxyglucose uptake, GLUT1 protein abundance, and GLUT1 mRNA abundance in ARL 15 cells. At 6 h of T3 treatment, 3H-2-deoxyglucose uptake was increased by 40 +/- 11%, whereas the abundance of GLUT1 protein in cell extracts had not yet changed at this time. At 48 h, GLUT1 protein was increased by 58 +/- 10%, whereas 3H-2-deoxyglucose uptake at this time was increased by 116 +/- 14%. GLUT1 mRNA levels rose within 4 h of T3 treatment, preceding the increase in GLUT1 protein, and more than doubled by 24 h. In additional experiments to determine the mechanism by which T3 increases GLUT1 mRNA, T3 treatment for 48 h increased the rate of transcription of the GLUT1 gene, determined by nuclear run-on analysis, by 55 +/- 11%. T3 treatment did not significantly alter the half-life of GLUT1 mRNA. In the presence of inhibitors of protein synthesis, GLUT1 mRNA increased at 6 h (5-7-fold), but there was no further induction of this mRNA by T3 in the presence of these inhibitors.(ABSTRACT TRUNCATED AT 250 WORDS)