Question

Thiazide also causes the renin-angiotensin system to activate. Explain this system (starting with renin) and why it would be counterproductive to Thiazide. Finish with why ACE inhibitors are usually proscribed with Thiazide.

Answer 1

Thiazide is a diuretic drug which helps reduce the blood pressure and is indicated in hypertension. It acts on the distal convulated renal tubule and inhibits sodium and chloride reabsorption.
Thiazide acts by inhibiting sodium/chloride pump in apical membrane.
Renin angiotensin system is a body's internal response to regulate the blood pressure. As the blood pressure decreases, the renal perfusion decreases which stimulates renin production from the kidneys. The renin acts on liver to release angiotensinogen which is converted to angiotensin l and angiotensin ll by angiotensin converting enzyme(ACE). The angiotensin acts blood vessels and causes them to vasoconstrict. It also stimulates adrenal gland and posterior pituitary to release aldosterone and ADH. Aldosterone and ADH increase sodium reabsorption from renal tubule and also increase water retention. This results in increased blpod volume and blood pressure.
As the RAS system acts to increase blood pressure it counteracts the action of Thiazide which decrease blood pressure by increasing sodium and water excretion in urine.
ACE inhibitors helps inhibit the angiotensinogen converting enzyme which results in limiting the conversion of angiotensinogen to angiotensin l and ll. Thus helps prevent activation of RAS system by kidneys which is counterproductive to thiazide.