d. Aldosterone. This is mineralocorticoid secreted by the adrenal medulla . It antagonizes atrial natriuretic peptide (ANP) stimulation of excretion of sodium and water by the kidneys.
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ANP is a hormone secreted by the cells of the right atrium of the heart; it is secreted in response to increased atrial stretch secondary to a rise in blood pressure. It controls electrolyte homeostasis by promoting sodium and water excretion by the kidneys. These effects function to lower blood pressure. Atriopeptin(ANP) is an aldosterone synthesis inhibitor. As would be expected, aldosterone opposes the actions of ANP. Aldosterone is secreted by the zona glomerulosa--the outermost layer of the adrenal cortex. Its secretion is promoted by the renal -angiotensin-aldosterone system, by the action of adrenocorticotropic hormone (ACTH), and by increases in serum concentration of potassium ions(K+).