In vitro evidence for modification of rat liver glucocorticoid receptor binding properties and transformation by hyperthermia.
The physico-chemical parameters of the interaction of [3H]triamcinolone acetonide (TA) with the glucocorticoid receptor (GR) and the in vitro activation of glucocorticoid-receptor complexes were studied in liver cytosols of rats exposed to 41 degrees C hyperthermia. A significant reduction in glucocorticoid binding and a slight increase in binding affinity were detected in hyperthermic rats as compared to the controls. The number of binding sites was 0.48 +/- 0.02 and 0.73 +/- 0.03 pmol/mg protein for heat-treated and control rats, respectively. Differences in equilibrium dissociation constants (0.52 +/- 0.08 nM for hyperthermic and 0.94 +/- 0.13 nM for control animals) were reflected in corresponding differences in dissociation rate constants at 25 degrees C (5.1 x 10(-4) and 7.5 x 10(-4) min-1, respectively), whereas association rate constants were similar. The inactivation kinetics of unoccupied GR at 25 degrees C was the same in both groups. Glucocorticoid-receptor complexes in liver cytosol from hyperthermic and control rats were thermally activated to a similar extent, but the activation rate was significantly lower in the former. Mixing experiments with the control and hyperthermic rat liver cytosols suggest that this impairment of glucocorticoid-receptor complexes activation could be at least in part ascribed to heat stress-related changes in the action of activation modulator(s). Sedimentation behaviour of unactivated and activated [3H]TA-receptor complexes of hyperthermic and control rats was identical.
Matić
G
G
Department of Molecular Biology and Biochemistry, Sinisa Stankovic Institute for Biological Research, Belgrade, Yugoslavia.
Trajković
D
D
Susa
M
M
Damjanović
S
S
Petrović
J
J
D000818:Animals; D003600:Cytosol / Q000378:metabolism; D005334:Fever / Q000378:metabolism*; D006358:Hot Temperature; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D014222:Triamcinolone Acetonide / Q000378:metabolism
D011965:Receptors, Glucocorticoid; D014222:Triamcinolone Acetonide