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In this presentation, I present evidence indicating a direct action of thyroid hormone at the level of the plasma membrane. Characteristically, the plasma membrane-mediated effects of thyroid hormones are prompt in onset, independent of new protein synthesis, and are associated with changes in the transmembrane transport of ions and substrates. The presence(More)
I have shown that cyclic AMP stimulates sugar uptake in rat thymocytes. However, trypsin treatment, which increases rat thymocyte cyclic AMP concentration, fails to increase sugar uptake. The purpose of the present study is to examine this seeming inconsistency, and to evaluate further the function of trypsin. Mild trypsin treatment of rat thymocytes(More)
At the physiological concentration of Ca2+, the presumed calcium ionophore A23187 produced dose-related increases in 45Ca uptake by rat thymocytes and decreases in cell viability, effects that displayed a strong linear correlation. In media containing a very low concentration of Ca2+ (7.10(-6) M), in contrast, ionophore A23187 had no specific effect on(More)
The uptake of 2-deoxy-D-[1-3H]glucose ([1-3H]DOG) by cultured chick embryo heart cells was stimulated by L-triiodothyronine (T3). This stimulation began with the exposure to T3, rose linearly for about 8 h and reached a plateau around 24h. Actinomycin D, puromycin and cyclohexmide had no effect on the stimulated sugar uptake during the first 6h. These(More)
We have previously demonstrated that in the rat thymocyte T3 produces a prompt, extranuclear effect to increase cellular cAMP concentration and 2-deoxyglucose (2-DG) uptake. We have also demonstrated the presence of specific receptors for T3 in the rat thymocyte plasma membrane. From these and other observations we have suggested that T3 initiates these(More)
Studies were conducted to ascertain the in vitro effect of 3,5,3'-triiodothyronine (T(3)) on the accumulation of the glucose analogue, 2-deoxyglucose (2-DG), by thymocytes freshly isolated from weanling rats. At a concentration of 1 muM, T(3) stimulated the 15-min uptake of (3)H-2-DG after cells had been exposed to T(3) for only 30 min. Significant(More)
The present experiments were designed to explore the mechanism whereby 3,5,3'-triiodothyronine (T3) stimulates the uptake of 2-deoxy-D-glucose (2-DG) in rat thymocytes in vitro. Addition of T3 evoked a transient, dose-related increase in cellular cyclic (c) AMP concentrations, evident within 5 min. followed soon by an increase in 2-DG uptake. The effects of(More)