a. A decrease in renal perfusion pressure causes the juxtaglomerular cells of the afferent arteriole to secrete renin.
b. Renin catalyzes the conversion of angiotensinogen to angiotensin I in plasma.
c. Angiotensin-converting enzyme (ACE) catalyzes the conversion of angiotensin I to angiotensin II, primarily in the lungs.
- ACE inhibitors (e.g., captopril) block the conversion of angiotensin I to angiotensin II and, therefore, decrease blood pressure.
d. Angiotensin II has two effects:
(1) It stimulates the synthesis and secretion of aldosterone by the adrenal cortex.
- Aldosterone increases sodium chloride (NaCl) reabsorption by the renal distal tubule, thereby increasing blood volume and arterial pressure.
- This action of aldosterone is slow because it requires new protein synthesis.
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