| Popis: |
The effect of triiodothyronine ( T 3 ) and insulin treatment on glucose metabolism in isolated adipocytes of 5 week old lean and obese Zucker rats was examined. Insulin had a strong stimulatory effect on glucose metabolism. Insulin stimulated and non-stimulated glucose utilization was greater in the obese than the lean rats. The effect of insulin and phenotype on glucose utilization was pathway specific as fatty acid, COg and glycerol-glyceride formation were stimulated by different magnitudes. Pretreatment of isolated adipocytes with pharmacological conce.itrations of T3 for 1/2 hour prior to measurement of glucose metabolism decreased fatty acid synthesis more in the adipocytes from lean than obese rats. The presence of insulin was required in the T3 pretreated cells to observe any effect of T3. The effect of a 2 hour pretreatment of adipocytes with T3 was dependent upon the phenotype of the cells, insulin status and the specific pathway of glucose utilization. The effect of T3 in the presence of insulin in both lean and obese adipocytes was to decrease lipogenesis. In the absence of insulin, the 2 hour pretreatment effect of T3 in tissue from a euthyroid animal was to increase lipogenesis at physiological concentrations and decrease lipogenesis at pharmacological concentrations. A pharmacological dose of T3 was required to increase lipogenesis in the absence of insulin in hypothyroid tissue. This is suggestive that obese tissue is resistant to thyroid hormones. However, in the presence of insulin, physiological levels of T3 decreased fatty |
