Question

describe the role of ANP in sodium and water excretion

Answer 1

Atrial Natriuretic Peptide (ANP) is secreted from cardiac muscle cells in atria when it senses atrial stretch due to increase in blood volume. Increase in blood volume causes increase in blood pressure. On sensing this ANP causes vasodilation of afferent arteriole of glomerulus apparatus this causes increase in renal blood flow and increase in glomerulus filteration rate. ANP also causes vasoconstriction of efferent arteriole of glomerulus apparatus which increases glomerulus filteration volume. All these effect of ANP along with inhibition of reabsorption of water in renal tubules leads to increase in excretion of water and urine volume thereby leading to diuresis. ANP also acts on collecting duct of nephron to reduce reabsorption of Na+ which enhances sodium excretion. ANP also acts on proximal tubule and inhibit Na+/H+ exchange and also inhibits reabsorption of Na+/Cl- in distal tube, both these actions of ANP also enhances sodium excretion. Hence the diuresis and naturesis caused by ANP reduces the blood volume and blood pressure.