Angiotensin and aldosterone

The object of this review is to describe the role of the renin–angiotensin system in control of aldosterone secretion. The review focuses on the roles of the circulating renin–angiotensin (RAS) system, the activity of which is determined predominantly by control of renin secretion from the kidney and on the role of the intra-adrenal RAS. Angiotensin can bind to two types of G protein coupled receptors, the AT₁ and AT₂ receptors. Both receptors are found on cells from the zona glomerulosa, the site of aldosterone synthesis. Angiotensin II acting via the AT₁ receptor stimulates the synthesis of aldosterone at early and late steps in the pathway. Its effect on aldosterone is influenced by a number of other factors such as plasma potassium levels, sodium status, other peptides such as ANP and adrenomedullin and proadrenomedullin N-terminal peptide. All components of the RAS are found in the adrenal gland. The activity of this intra-adrenal RAS is unmasked and amplified in nephrectomised animals. Aldosterone controls sodium transport across epithelial cells, but recently novel effects on the heart have been described.