Info

High Blood Pressure Exercise Program

Most Effective Hypertension Home Remedies

Get Instant Access

Figure 29-15

Effect of excessive angiotensin II formation and effect of blocking angiotensin II formation on the renal-pressure natriuresis curve. Note that high levels of angiotensin II formation decrease the slope of pressure natriuresis, making blood pressure very sensitive to changes in sodium intake. Blockade of angiotensin II formation shifts pressure natriuresis to lower blood pressures.

Importance of Angiotensin II in Increasing Effectiveness of Pressure Natriuresis. The importance of angiotensin II in making the pressure natriuresis mechanism more effective is shown in Figure 29-15. Note that when the angiotensin control of natriuresis is fully functional, the pressure natriuresis curve is steep (normal curve), indicating that only minor changes in blood pressure are needed to increase sodium excretion when sodium intake is raised.

In contrast, when angiotensin levels cannot be decreased in response to increased sodium intake (high angiotensin II curve), as occurs in some hypertensive patients who have impaired ability to decrease renin secretion, the pressure natriuresis curve is not nearly as steep. Therefore, when sodium intake is raised, much greater increases in arterial pressure are needed to increase sodium excretion and maintain sodium balance. For example, in most people, a 10-fold increase in sodium intake causes an increase of only a few millimeters of mercury in arterial pressure, whereas in subjects who cannot suppress angiotensin II formation appropriately in response to excess sodium, the same rise in sodium intake causes blood pressure to rise as much as 50 mm Hg. Thus, the inability to suppress angiotensin II formation when there is excess sodium reduces the slope of pressure natriure-sis and makes arterial pressure very salt sensitive, as discussed in Chapter 19.

The use of drugs to block the effects of angiotensin II has proved to be important clinically for improving the kidneys' ability to excrete salt and water. When angiotensin II formation is blocked with an angiotensin-converting enzyme inhibitor (see Figure 29-15) or an angiotensin II receptor antagonist, the renal-pressure natriuresis curve is shifted to lower pressures; this indicates an enhanced ability of the kidneys to excrete sodium because normal levels of sodium excretion can now be maintained at reduced arterial pressures. This shift of pressure natriuresis provides the basis for the chronic blood pressure-

Figure 29-15

Effect of excessive angiotensin II formation and effect of blocking angiotensin II formation on the renal-pressure natriuresis curve. Note that high levels of angiotensin II formation decrease the slope of pressure natriuresis, making blood pressure very sensitive to changes in sodium intake. Blockade of angiotensin II formation shifts pressure natriuresis to lower blood pressures.

lowering effects in hypertensive patients of the angiotensin-converting enzyme inhibitors and angiotensin II receptor antagonists.

Was this article helpful?

0 0
Reducing Blood Pressure Naturally

Reducing Blood Pressure Naturally

Do You Suffer From High Blood Pressure? Do You Feel Like This Silent Killer Might Be Stalking You? Have you been diagnosed or pre-hypertension and hypertension? Then JOIN THE CROWD Nearly 1 in 3 adults in the United States suffer from High Blood Pressure and only 1 in 3 adults are actually aware that they have it.

Get My Free Ebook


Post a comment