Question

Describe the Renin-Angiotensin-Aldosterone System.

ACE inhibitors are commonly prescribed meds for hypertension. Why do these work to lower BP?

In your opinion, does the use of ACE inhibitors address the causative problem of hypertension (meaning: do all hypertensives have overactive Angiotensin Converting Enzymes?)? Be sure to thoroughly explain your position from the standpoint of this unit AND previous unit material.

Answer 1

1 Sodium is a normal constituent of urine and the amount excreted is regulated by the hormone aldosterone,secreted by the adrenal cortex.Cells in the afferent arteriole of the nephron are stimulated to produce the enzyme renin by sympathetic stimulation ,low blood volume or by low arterial blood pressure.Renin converts the plasma protein angiotensinogen ,produced by the liver ,to angiotensin.Angiotensin converting enzyme ,formed in small quantities in the lungs ,proximal convoluted tubules and other tissues convert angiotensin 1 into angiotensin,which is a very potent vasoconstrictor and increases blood pressure .Renin and raised blood potassium levels also stimulate the adrenal gland to secrete aldosterone .Water is reabsorbed with sodium and together they increase the blood volume,leading to reduced renin secretion through the negative feedback mechanism.When sodium reabsorption is increased potassium excretion is increased,indirectly reducing intracellular potassium.

2 Angiotensin 2 is a hormone which helps in retaining water and result in fluid retaining in restricted spaces which makes the blood pressure rise.When this hormone enters into the blood ,the blood vessels becomes more narrrow and gives less space for blood to move ,resulting in increased blood pressure.ACE inhibitors lowers the blood pressure by reducing angiotensin 2 in the body,making the blood vessels to relax and widen,allowing the blood to flow more easier and also it lowers the amount of water retained in the body which lowers the blood pressure.

3 ACE inhibitors are agents for congestive heart failure ,in combination with other agents such as diuretics,thromboltic agents,aspirin,betablockers,nitrates,angiotensin 2 receptor blockers and digoxin.ACE inhibitors can be usefully employed in the treatment of heartfailure,in which they reduce both pre- and after-load and mainly of hypertension.Two drugs namely captopril and enalapril exert their hypotensive action without the development of pseudo-tolerance or tolerance.