Novel, Membrane-Intrinsic Receptors for Progesterone and Aldosterone
In 1972, binding of [3H] aldosterone to plasma membranes from rat kidney with Kd ~ 100 nM was reported . In a similar system, solubilization of binding activity was performed, but no further identification had been achieved . Apart from these studies in the classical mineralocorticoid target organ, Armanini et al.  reported specific high-affinity binding of [3H] aldosterone to mononuclear leukocytes. The dissociation constant Kd was 2.7 nM with a binding site density of 209 sites per cell. The order of binding affinities was aldosterone ≈ deoxycorticosterone ≈ corticosterone > hydrocortisone > dexamethasone, which differs from the selectivity profile of the classic nuclear mineralocorticoid receptor (MR). Microsomal membranes from mononuclear leukocytes were subjected to photochemical crosslinking with the radioligand aldosterone-3-(0-carboxymethyl)-oximino-(2-[125I]iodohistamine) in the presence and absence of an excess of unlabeled aldosterone. After SDS electrophoresis, a prominent maximum was visible at ~50 kDa which could be displaced by aldosterone, but not Cortisol . Later, plasma membrane preparations from porcine kidney were studied with regard to non-classical receptors.
KeywordsCortisol Testosterone Dexamethasone Progesterone Tryptophan
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