Covalent affinity labeling, radioautography, and immunocytochemistry localize the glucocorticoid receptor in rat testicular Leydig cells.
The presence and distribution of glucocorticoid receptors in the rat testis were examined by using 2 approaches: in vivo quantitative radioautography and immunocytochemistry. Radioautographic localization was made possible through the availability of a glucocorticoid receptor affinity label, dexamethasone 21-mesylate, which binds covalently to the glucocorticoid receptor, thereby preventing dissociation of the steroid-receptor complex. Adrenalectomized adult rats were injected with a tritiated (3H) form of this steroid into the testis and the tissue was processed for light-microscope radioautography. Silver grains were observed primarily over the Leydig cells of the interstitial space and to a lesser extent, over the cellular layers which make up the seminiferous epithelium, with no one cell type showing preferential labeling. To determine the specificity of the labeling, a 25- or 50-fold excess of unlabeled dexamethasone was injected simultaneously with the same dose of (3H)-dexamethasone 21-mesylate. In these control experiments, a marked reduction in label intensity was noted over the Leydig as well as tubular cells. Endocytic macrophages of the interstitium were non-specifically labeled, indicating uptake of the ligand possibly by fluid-phase endocytosis. A quantitative analysis of the label confirmed the presence of statistically significant numbers of specific binding sites for glucocorticoids in both Leydig cells and the cellular layers of the seminiferous epithelium; 86% of the label was found over Leydig cells, and only 14% over the cells of the seminiferous epithelium. These binding data were confirmed by light-microscope immunocytochemistry using a monoclonal antibody to the glucocorticoid receptor.(ABSTRACT TRUNCATED AT 250 WORDS)
Stalker
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Department of Anatomy, McGill University, Montreal, Quebec, Canada.
Hermo
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Antakly
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D000345:Affinity Labels; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D001345:Autoradiography; D003907:Dexamethasone / Q000031:analogs & derivatives; D007150:Immunohistochemistry; D007985:Leydig Cells / Q000378:metabolism / Q000648:ultrastructure*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011965:Receptors, Glucocorticoid / Q000276:immunology / Q000378:metabolism*; D014316:Tritium
D000345:Affinity Labels; D000911:Antibodies, Monoclonal; D011965:Receptors, Glucocorticoid; D014316:Tritium; D003907:Dexamethasone; C031710:dexamethasone 21-methanesulfonate