Glucocorticoid receptors in epithelial cells isolated from the mammary glands of pregnant and lactating rats.
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.
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*
D011965:Receptors, Glucocorticoid; D011987:Receptors, Steroid; D000450:Aldosterone; D011374:Progesterone; D003907:Dexamethasone