ABSTRACT
This chapter examines some main components of the renin-angiotensin-aldosterone (RAA) system, their sources, properties, actions and termination of action. It presents some examples of drugs developed through knowledge of the RAA, and their uses. The RAA system is an endocrine hormone system important in the regulation of blood fluid volume and systemic blood pressure. Renin is an endocrine enzyme hormone secreted by the juxtaglomerular apparatus of the kidney; renin is released in response to a fall in blood pressure or an abnormal rise in blood osmolality; renin catalyses the release in blood of angiotensin. Angiotensin II constricts efferent glomerular arterioles preferentially, thus ensuring that the glomerulus continues to be adequately perfused in order to maintain the glomerular filtration rate. Constriction of afferent arterioles feeding capillary beds results in increased arteriolar resistance, which causes a rise in blood pressure.
