Insulin modulates rat liver glucocorticoid receptor

R. Isenovic, Esma and Zakula, Zorica and Koricanac, G. and Ribarac-Stepic, Nevena (2006) Insulin modulates rat liver glucocorticoid receptor. Acta Biologica Hungarica, 57 (1). pp. 37-48. ISSN 0236-5383

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Abstract

This investigation used cytosol fraction of rat liver to examine the effects of insulin (INS) on functional properties of glucocorticoid receptor (GR). Male Wistar rats (220–250 g b.wt.) were injected with INS (50 μ g/200 g b.wt, i.p.) and 18 h after INS administration used for experiments. INS-stimulated dissoci- ation of G-R complexes was significantly increased by 133% compared to control level. However, INS treatment significantly stimulated stability of GR protein by 138% above control value. Furthermore, results show that INS stimulated activation of formed cytosol [ 3 H] TA-R complexes by 143% in respect to control. [ 3 H]TA-R complexes from INS treated animals could be activated and accumulated at higher rate in cell nuclei of control animals. The physiological relevance of the data was confirmed by INS- related stimulation of Tryptophan oxigenase (TO) activity. It was observed that INS stimulated TO activ- ity while INS injected to adrenalectomized rats, exhibited less effects compared to control. The results indicate that a glucocorticoid hormone (CORT) enhances INS induced stimulation of TO activity, as evi- denced by enhanced enzyme activity. Presented data suggest: that INS treatment leads to modifications of the GR protein and the nuclear components and that INS activates the rat liver CORT signaling path- way which mediates, in part, the activity of TO.

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