THE SUBCELLULAR-DISTRIBUTION OF GLUCOCORTICOID-RECEPTOR COMPLEXES AS STUDIED BY CHEMICAL CROSS-LINKING OF INTACT HTC CELLS

Treatment of intact HTC cells with glutaraldehyde results in redistrib ution of glucocorticoid binding sites between cytosolic and nuclear fr actions. The decrease in cytosolic receptors and their accumulation at the nuclear level were found to be directly related to the glutaralde hyde concentrations employed in our procedure and inversely related to the cell density of samples. When the data from eleven separate exper iments were combined, and analyzed by linear regression of cytosolic a nd nuclear levels of receptor complexes vs the ratios between the DNA and glutaraldehyde concentration of our samples, two lines were obtain ed whose intercepts on the ordinate yielded values of cytosolic and nu clear receptors corresponding to 37.5 and 62.5% of the total cellular pool, respectively. When we compared the subcellular redistribution of glucocorticoid receptor to that of the cytosolic enzyme lactate dehyd rogenase upon HTC cell crosslinking with glutaraldehyde, we found that the cytosolic and nuclear levels of the enzyme were 53.2 and 46.8% of the total content, respectively. If the subcellular distribution of g lucocorticoid receptor is corrected for the artefactual redistribution induced by crosslinking, using the values obtained for lactate dehydr ogenase, it can be concluded that glucocorticoid receptors in HTC cell s are distributed between cytosol and nuclei in a ratio which is about 2:1. Our findings lend further support to the conclusion that only a portion of glucocorticoid receptor is cytosolic in intact cells.