The effect of homogenization temperature upon the apparent cellular compartmentalization of unoccupied estrogen receptor

Alteration of glucocorticoid receptor subcellular distribution by hyperthermic stress

The aim of the present study was to examine intracellular redistribution of the glucocorticoid receptor (GR) in rat liver cells during a 24-h time period after exposure of the animals to 41?C whole body hyperthermic stress. The level of the receptor protein in the cytoplasmic and nuclear compartments was measured by immunoblotting procedures applied to both crude cytosol and immunopurified GR, as well as by immunocytochemical analyses applied to both paraffin-embedded liver sections and unfixed nuclear smears. All the experimental approaches employed in the study provided similar results, demonstrating that the transient stress-related decline of the cytoplasmic GR observed during the first five hours after exposure of the animals to whole-body hyperthermic stress is accompanied by enhanced nuclear accumulation of the receptor. The study can contribute to a better understanding of the influence of stress on the glucocorticoid signal transduction pathway. .

Preferential nuclear binding of estrogen in the formalin-fixed rat uterus

Rat uterus fixed overnight in buffered formalin retains the ability to specifically bind estradiol. However, the estrogen binding property of fixed tissue appears preferentially localized in the nuclear fraction regardless of hormonal status. Furthermore, the quantity of the nuclear estrogen receptor in fresh or fixed uterus is virtually identical in the presence or absence of estrogenic hormone. Yet, while both tissue preparations exhibit equivalent increases in the total nuclear receptor occupancy after hormone exposure, only the fresh uterus contains a major cytosolic estrogen binder which decreases in availability upon the estrogen-induced elevation of the nuclear bound steroid. However, the cytosolic estrogen receptor exhibits a significant loss in its ligand binding property after formalin exposure. Thus, the preferential localization of estrogen binding in the nuclear fraction of fixed whole tissue may just reflect that only the tightly bound nuclear estrogen receptor's functional and/or structural integrity survives long-term formation fixation. Our observation of estrogen binding in preserved tissue may also be a clinically useful tool in therapy analysis.