title: Glucocorticoid receptors in epithelial cells isolated from the mammary glands of pregnant and lactating rats.
abstract: We have isolated epithelial cell clusters from mammary glands of pregnant and lactating rats by collagenase-hyaluronidase-deoxyribonuclease digestion, followed by Ficoll density-gradient centrifugation. Clusters of greater than 90% viable cells were identified by light microscopy as essentially devoid of other cell types; the integrity of their subcellular organelles verified by electron microscopy. Binding characteristics of the synthetic glucocorticoid [3H]dexamethasone were studied in cytosols prepared from isolated cell clusters. Cytosols from both pregnant and lactating rats bound [3H]dexamethasone with high affinity to a single class of low capacity binding sites. In both types of cytosol the dissociation constant (Kd 4 degrees C approximately/nM) of the binding was similar; the number of sites per cell in lactating rats was approximately double that in pregnant rats. The specificity of binding was typical of a classical glucocorticoid receptor, with a hierarchy of affinity by competition studies dexamethasone greater than progesterone greater than aldosterone much much greater than testosterone = estradiol. In particular, no difference in progesterone affinity for these glucocorticoid receptors was seen between pregnancy and lactation. This suggests that reported differences in inhibitory action of progesterone, pregnancy versus post-partum, are not glucocorticoid-receptor mediated.
mesh_terms: D000450:Aldosterone / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002469:Cell Separation; D002478:Cells, Cultured; D003907:Dexamethasone / Q000494:pharmacology; D004847:Epithelial Cells; D005260:Female; D007774:Lactation; D008321:Mammary Glands, Animal / Q000032:analysis*; D011247:Pregnancy; D011270:Pregnancy, Animal; D011374:Progesterone / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D011965:Receptors, Glucocorticoid / Q000302:isolation & purification*; D011987:Receptors, Steroid / Q000302:isolation & purification*
chemical_list: D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D000450:Aldosterone; D011374:Progesterone; D003907:Dexamethasone