Chapter 20 - Section 20.2 - Blood Pressure, Resistance, and Flow - Apply What You Know - Page 757: 1

Renin inhibitors are a class of drugs used to treat hypertension (high blood pressure) by targeting the renin-angiotensin-aldosterone system (RAAS). The RAAS is a hormonal system that plays a crucial role in regulating blood pressure and fluid balance in the body. Renin is an enzyme that initiates the RAAS cascade. Here's how renin inhibitors produce the desired effect of lowering blood pressure: 1. **Normal RAAS Function and Hypertension:** The RAAS is activated when blood pressure drops or blood volume decreases. Renin, released by the kidneys in response to various signals, converts angiotensinogen (a protein produced by the liver) into angiotensin I. Angiotensin I is further converted into angiotensin II by the angiotensin-converting enzyme (ACE), primarily found in the lungs. Angiotensin II is a potent vasoconstrictor, which means it narrows blood vessels, causing them to constrict. It also stimulates the release of aldosterone from the adrenal glands. Aldosterone promotes the reabsorption of sodium and water in the kidneys, leading to increased blood volume. Both vasoconstriction and increased blood volume contribute to elevated blood pressure. 2. **Role of Renin Inhibitors:** Renin inhibitors directly target the initial step of the RAAS cascade by blocking the activity of renin. By inhibiting renin, these drugs prevent the conversion of angiotensinogen to angiotensin I. As a result, the production of angiotensin II is reduced. 3. **Effects of Renin Inhibition:** By reducing the production of angiotensin II, renin inhibitors have several effects that collectively lead to a decrease in blood pressure: - **Vasodilation:** Angiotensin II is a vasoconstrictor, and its reduced levels result in the relaxation and dilation of blood vessels. This widens the blood vessels and lowers resistance to blood flow, reducing blood pressure. - **Decreased Aldosterone Release:** Lower levels of angiotensin II lead to reduced stimulation of aldosterone release. As a result, there is decreased sodium and water reabsorption in the kidneys, leading to a decrease in blood volume. - **Antiproliferative Effects:** Angiotensin II is involved in cellular growth and proliferation in blood vessels. Inhibiting its production can help prevent the thickening of vessel walls (hypertrophy) that contributes to hypertension. In summary, renin inhibitors lower blood pressure by interrupting the renin-angiotensin-aldosterone system at its initial step, reducing the production of angiotensin II. This results in vasodilation, decreased aldosterone release, and antiproliferative effects, all of which contribute to a decrease in blood pressure and improved management of hypertension.

Renin inhibitors are a class of drugs used to treat hypertension (high blood pressure) by targeting the renin-angiotensin-aldosterone system (RAAS). The RAAS is a hormonal system that plays a crucial role in regulating blood pressure and fluid balance in the body. Renin is an enzyme that initiates the RAAS cascade. Here's how renin inhibitors produce the desired effect of lowering blood pressure: 1. **Normal RAAS Function and Hypertension:** The RAAS is activated when blood pressure drops or blood volume decreases. Renin, released by the kidneys in response to various signals, converts angiotensinogen (a protein produced by the liver) into angiotensin I. Angiotensin I is further converted into angiotensin II by the angiotensin-converting enzyme (ACE), primarily found in the lungs. Angiotensin II is a potent vasoconstrictor, which means it narrows blood vessels, causing them to constrict. It also stimulates the release of aldosterone from the adrenal glands. Aldosterone promotes the reabsorption of sodium and water in the kidneys, leading to increased blood volume. Both vasoconstriction and increased blood volume contribute to elevated blood pressure. 2. **Role of Renin Inhibitors:** Renin inhibitors directly target the initial step of the RAAS cascade by blocking the activity of renin. By inhibiting renin, these drugs prevent the conversion of angiotensinogen to angiotensin I. As a result, the production of angiotensin II is reduced. 3. **Effects of Renin Inhibition:** By reducing the production of angiotensin II, renin inhibitors have several effects that collectively lead to a decrease in blood pressure: - **Vasodilation:** Angiotensin II is a vasoconstrictor, and its reduced levels result in the relaxation and dilation of blood vessels. This widens the blood vessels and lowers resistance to blood flow, reducing blood pressure. - **Decreased Aldosterone Release:** Lower levels of angiotensin II lead to reduced stimulation of aldosterone release. As a result, there is decreased sodium and water reabsorption in the kidneys, leading to a decrease in blood volume. - **Antiproliferative Effects:** Angiotensin II is involved in cellular growth and proliferation in blood vessels. Inhibiting its production can help prevent the thickening of vessel walls (hypertrophy) that contributes to hypertension. In summary, renin inhibitors lower blood pressure by interrupting the renin-angiotensin-aldosterone system at its initial step, reducing the production of angiotensin II. This results in vasodilation, decreased aldosterone release, and antiproliferative effects, all of which contribute to a decrease in blood pressure and improved management of hypertension.