In vivo stimulation of sugar uptake in rat thymocytes. An extranuclear action of 3,5,3'-triiodothyronine.

Abstract

In previous studies we have demonstrated that 3,5,3'-triiodothyronine (T3) in vitro produces a prompt increase in the uptake of the sugar analogue 2-deoxyglucose (2-DG) by freshly isolated rat thymocytes. This effect is prompt, being evident at 20 min after addition of T3, is independent of new protein synthesis, and can be elicited by physiologic concentrations of the hormone. In the present studies, we have sought to determine whether physiologic doses of T3 are capable of inducing an increase in 2-DG uptake in the thymocytes of the living animal. Therefore, 26-28-d-old female rats were injected with increasing doses of i.v. T3, followed 60 min later by 3H-labeled 2-DG. 30 min later, animals were killed, thymocytes were isolated, and their 3H content determined. Uptake of PH12-DG was increased by T3 in a dose-dependent manner. The lowest effective dose was 10 ng/ 100 g of body weight (30% above control) and the maximally effective dose 1 gg/100 g of body weight (116% above control). The effect of T3 was independent of new protein synthesis in that it was not blocked by a dose of cycloheximide that inhibited the incorporation of 13Hlleucine into thymocyte protein by 92- These studies indicate that T3 in physiologic doses acts in vivo to increase the uptake of sugar by rat thymocytes by a mechanism that is extranuclear in origin, in that it is independent of new protein synthesis. The findings support the conclusion that the previously demonstrated effects of T3 on thymocyte sugar uptake in vitro, which seem clearly to be mediated at the level of the plasma membrane, have physiologic relevance. IntroductionWe have previously demonstrated that 3,5,3'-triiodothyronine (T3)' increases the uptake ofthe glucose analogue 2-deoxyglucose (2-DG) in isolated rat thymocytes in vitro (1-5). This effect of T3 is evident within 20 min after the addition of the hormones;

Thyroid hormone inhibition in L6 myoblasts of IGF-I-mediated glucose uptake and proliferation: new roles for integrin αvβ3

“…Glucose uptake in skeletal muscle cells has been well characterized in the last 20 years by several groups (4,5,24,59,61,69). We carried out experiments to confirm our experimental model, measuring glucose uptake in L6 myoblasts induced by 0.1 nM insulin or 10 nM IGF-I ( Fig.…”

Effects of Thyroid Hormones on Heart and Kidney Functions

“…One such possibility is an effect on basolateral membrane potassium conductive pathof T 3 induced a fast, dose-and time-dependent increase in fluid reabsorption [11]. The direct effect of thyroid ways [29]. Indeed it has been demonstrated that, in rat diaphragm and liver cells, single administration of high hormones on tubular transport processes has been confirmed by experiments designed to compare the time doses of T 3 to euthyroid rats increased the potassium permeability of the cell membrane well before a rise in course in changes in GFR, filtered sodium load and specific transport systems: it was found that, after a single Na-K-ATPase activity was observed [30][31][32].…”

Nongenomic Actions of Thyroid Hormone and Intracellular Calcium Metabolism

“…Segal and Inbar showed 20 years ago that physiological concentrations of T 3 -activated glucose transport in rat thymocytes [14,15,61]. This was a novel effect of thyroid hormone that was extranuclear in mechanism, that is, independent of protein synthesis [61].…”

“…This was a novel effect of thyroid hormone that was extranuclear in mechanism, that is, independent of protein synthesis [61]. Segal proposed that the effect was mediated by the interaction of thyroid hormone with a putative membrane receptor since cytoplasmic free concentration rose promptly as a consequence of an influx of Ca 2+ from the extracellular medium, and was associated with a calmodulin-mediated activation of adenylate cyclase, increase in cAMP, and increase in activity of the membrane glucose transporter [15].…”