Corticosteroid receptors in the kidney of chick embryo. III. Nature, properties, and ontogeny of aldosterone receptor.
An aldosterone receptor in the cytosol from kidney of chick embryos which had a sedimentation coefficient of 8.2 S and a molecular weight higher than 100,000 was identified. Kinetic analysis at 4 degrees revealed a rapid association of the hormone to the receptor that followed second-order reaction kinetics and a dissociation of pseudo-first-order reaction kinetics. The association (ka) and dissociation (kd) rate constants were, respectively, 4.94 X 10(5) M-1 sec-1 and 8.33 X 10(-6) sec-1. From their ratio a KA value of 5.9 X 10(10) M-1 was calculated. In a series of experiments performed with kidneys of 17-day-old embryos, the KA at equilibrium, obtained from the Scatchard plot, was 3.1 +/- 1.2 X 10(8) M-1, whereas the Nmax was 172 +/- 14 fmol/mg protein. Competition studies with various steroids demonstrated that corticosterone had an affinity for the receptor close to that of aldosterone, thus suggesting a degree of resemblance of the mineralo- and glucocorticoid receptors in the chick embryo. However, the profiles of the binding affinities and capacities during the embryogenesis showed that the aldosterone-binding sites had a pattern completely different from that of the glucocorticoid receptor, indicating that the two receptors are most likely separate entities.
D000450:Aldosterone / Q000378:metabolism*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D002642:Chick Embryo / Q000378:metabolism*; D002850:Chromatography, Gel; D003907:Dexamethasone / Q000378:metabolism; D005938:Glucocorticoids / Q000378:metabolism; D007668:Kidney / Q000196:embryology / Q000378:metabolism*; D007700:Kinetics; D008954:Models, Biological; D008970:Molecular Weight; D011965:Receptors, Glucocorticoid / Q000378:metabolism*; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid / Q000378:metabolism*
D005938:Glucocorticoids; D011965:Receptors, Glucocorticoid; D018161:Receptors, Mineralocorticoid; D011987:Receptors, Steroid; D000450:Aldosterone; D003907:Dexamethasone