2. Renal effects that include marked sodium reabsorption in the proximal kidney tubules.
3. Adrenal effects that cause the release of aldosterone, which enhances sodium and water reabsorption and potassium excretion in the renal tubule distal to the macula densa. Angiotensin II promotes release of catecholamines from the adrenal glands.
4. There is an increase in sympathetic outflow that facilitates ganglionic stimulation of the sympathetic nervous system.
Stimuli to the release of renin include: (1) a decrease in renal blood flow, hypotension, and reduction of intra-vascular volume; (2) sodium depletion or sodium diuresis; and (3) beta-adrenergic receptor activation.
ACE inhibitors are competitive inhibitors of angio-tensin-converting enzyme and therefore prevent the conversion of angiotensin I to angiotensin II. This action causes the salutary effects listed below.
1. There is dilatation of arteries which causes a reduction in total systemic vascular resistance resulting in a fall in blood pressure and a reduction in afterload. This allows the left ventricle to pump blood more easily into the arterial system. Thus, the left ventricle has less work to do and this action prevents or improves heart failure (see the section Pathophysiology in the chapter Heart Failure).

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