Glucocorticoid receptor and Tryptophan oxygenase activity in streptozotocin treated rats.

Abstract

The goal of this study was to examine the possible effects of the insulin on the functional properties of the glucocorticoid receptor (GR), in the rat liver, as well as its equilibrium binding constant (Kd) and number of binding sites (q), in order to contribute to elucidation of the molecular basis of the relationship between insulin and glucocorticoids in regulation of cell processes. Biological consequences of their interactions were judged on the basis of changes in GR as well as in the activity of Tryptophan oxygenase (TO). The experiments were perfomed on male nonadrenalectomized Wistar strain rats, treated by streptozotocin as well as adrenalectomized animals These group of animals were injected by insulin (25ug/100g b.w.) 18 hours before analysis. The obtained results have shown that the Kd in all experimental groups of animal was in the interval: 1.87-4.027nM. However, the injected insulin in all experimental groups increased the number of GR, while in streptozotocin treated rats, this increase was 1.5 fold, compared to the values obtained for corresponding controls. TO activity was increased (2-3 fold), in liver of insulin treated rats, except in the case of adrenalectomized animals, while the enzyme activity in streptozotocin treated rats was up to 3 fold, in respect to the appropriate control value. These evidences suggest that mechanisms of cooperative effects of insulin and glucocorticoid on regulation of cell function involve the modulation of hormone signals transmited through changes in number and functionality of GR proteins.