ANP acts at the: September 2009

Ans. C: Collecting tubule ANP act on the collecting tubule and duct to increase Na+ excretion. It produce this effect by dilating afferent aerioles and relaxing mesangial cells. Both of these actions increase glomerular filtration. In addition, it act on the renal tubules to inhibit Na+ reabsorption. Other actions include an increase in capillary permeability, leading to extravasation of fluid and a decline in blood pressure. In addition, it relax vascular smooth muscle in aerioles and venules. These peptides also inhibit renin secretion and counteract the pressor effects of catecholamines and angiotensin II. In the brain, ANP is present in neurons, and an ANP-containing neural pathway projects from the anteromedial pa of the hypothalamus to the areas in the lower brainstem that are concerned with neural regulation of the cardiovascular system. In general, the effects of ANP in the brain are opposite to those of angiotensin II, and ANP-containing neural circuits appear to be involved in lowering blood pressure and promoting natriuresis.