[Aldosterone receptors: new insights in hormonal signal transduction]

Aldosterone exerts its effects by binding to an intracellular receptor, the mineralocorticoid receptor (MR), that belongs to the superfamily of ligand-regulated transcription factors. This family includes receptors for steroid and thyroid hormones, vitamin D and retinoids and also orphan receptors with unidentified ligands. All the members of this family display a modular structure composed of a transactivation domain, a DNA binding domain and a ligand binding domain. Upon hormone binding, the receptor undergoes a series of structural modifications leading to its interaction with DNA sequences and transcriptional modulation of specific genes. Since the level of circulating glucocorticoids is 100-1000 fold higher than that of aldosterone and the affinity of the MR is identical for glucocorticoids and aldosterone, the question of the mechanisms responsible for the in vivo selectivity of aldosterone for its receptor arises. The mechanisms of cellular and tissular selectivity involved in the physiological response of aldosterone are discussed in this review.