The zona glomerulosa of the cortex makes mineralocorticoids like aldosterone.
Aldosterone is a fat-soluble, steroid hormone that is responsible for regulating sodium concentrations in the kidneys, which helps balance blood pressure.
When blood pressure or blood flow slows, macula densa cells in the kidney stimulate the kidney to release renin. Renin activates the Renin-Angiotensin-Aldosterone-System (RAAS). Renin causes angiotensinogen from the liver to become angiotensin I, which goes to the lungs and is converted to angiotensin II by the angiotensin-converting enzyme (ACE). Angiotensin II acts as a vasoconstrictor, signals the release of ADH from the neurohypophysis, and signals the adrenal gland's cortex to secrete aldosterone.
Aldosterone acts on receptors in the collecting duct and distal tubules to retain sodium, but an indirect action of this is water retention. Following osmotic principles, water will follow sodium into the blood vessels becoming more hypertonic than the tubules. Aldosterone levels are controlled by a negative feedback loop and once the blood pressure and salt levels reach normal levels, the pathway is shut off. Natriuretic peptide hormones from the heart have antagonist effects to aldosterone.
