TRIIODOTHYRONINE INCREASES GLUCOSE-TRANSPORTER ISOTYPE-4 MESSENGER-RNA EXPRESSION, GLUCOSE-TRANSPORT, AND GLYCOGEN-SYNTHESIS IN ADULT-RAT CARDIOMYOCYTES IN LONG-TERM CULTURE

Effects of T3 treatment (day 2-day 12) on the expression of the insuli n-regulated GLUT4, on 2-deoxyglucose uptake, and on glycogen synthesis were studied in ARC after 12 days of culture in T3-depleted 20% fetal calf serum. GLUT4 mRNA expression was low in controls, but increased in a dose-dependent manner by T3 treatment up to 2.8-fold at 100 nM. I n parallel, 100 nM T3 increased basal 2-deoxyglucose uptake 1.95-fold and insulin-stimulated uptake 1.75-fold. In addition, T3 enhanced basa l and insulin-stimulated [C-14] glucose incorporation into glycogen 1. 86- and 1.5-fold, respectively. Hence, ARC may meet part of their incr eased energy requirements in response to T3 by enhancing GLUT4 express ion. (C) 1996 Academic Press, Inc.