Kidneys and blood pressure

Gollasch, M. and Nelson, M.T. (1998) Voltage-dependent Ca channels in arterial smooth muscle. Kidney and Blood Pressure Research, 20 355-371. 

Atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP) are members of a family of so-called natriuretic peptides, synthesized predominantly in the cardiac atrium, ventricle, and vascular endothelial cells, respectively (G13, Y2). ANP is a 28-amino-acid polypeptide hormone released into the circulation in response to atrial stretch (L3). ANP acts (Fig. 8) on the kidney to increase sodium excretion and glomerular filtration rate (GFR), to antagonize renal vasoconstriction, and to inhibit renin secretion (Ml). In the cardiovascular system, ANP antagonizes vasoconstriction and shifts fluid from the intravascular to the interstitial compartment (G14). In the adrenal cortex, ANP is a powerful inhibitor of aldosterone synthesis (E6, N3). At the hypothalamic level, ANP inhibits vasopressin secretion (S3). It has been shown that some of the effects of ANP are mediated via a newly discovered hormone, called adreno-medullin, controlling fluid and electrolyte homeostasis (S8). The diuretic and blood pressure-lowering effect of ANP may be partially due to adrenomedullin (V5). 

Vertebrates also show expression of AADC in both neural and non-neural tissues. AADC has been purified from kidney (Christenson et al., 1972), liver (Ando-Yamamoto et al., 1987), adrenal medulla (Albert et al., 1987), and pheochromocytoma (Coge et al., 1989 Ichinose et al., 1989). In the adrenal medulla dopamine is further processed into epinephrine and norepinephrine, which are released from the chromaffin cells during stress to increase heart rate and blood pressure. There are no detectable monoamines in the liver and kidney, and the function of AADC in these tissues is unknown. AADC activity has also been... 

A decrease in blood volume or blood pressure may result in a decrease in the blood flow to the kidney. The kidney monitors renal blood flow by way of stretch receptors in the vessel walls. A decrease in renal blood flow stimulates the release of renin. The subsequent secretion of aldosterone causes retention of sodium and water and, therefore, an increase in blood volume and blood pressure back to normal. An increase in renal blood flow tends to cause the opposite effect. 

There are seven membrane forms of GC, designated GC-A to GC-G [33], Two forms, GC-A and GC-B (Mr = 120kDa), serve as receptors for atrial natriuretic peptide (ANP) and related peptides. ANP is a 28-amino-acid peptide isolated originally from cardiac atria as an important factor in the regulation of sodium excretion and blood pressure. GC-A binds ANP, as well as brain natriuretic peptide (BNP), and is located in vascular tissue and kidney. 

So, drugs that block jSj-receptors lower the heart rate and blood pressure and hence are used in conditions when the heart itself is deprived of oxygen. They are routinely prescribed in patients with ischemic heart disease. In addition, j3-blockers prevent the release of renin, which is a hormone produced by the kidneys which leads to constriction of blood... 

The renin-angiotensin system involves several endogenous components that help regulate vascular tone in various organs and tissues.25,84,109 In systemic circulation, the renin-angiotensin system acts by a sequence of events summarized in Figure 21-2. Renin is an enzyme produced primarily in the kidneys. When blood pressure falls, renin is released from the kidneys into the systemic circulation. Angiotensinogen is a peptide that is produced by the liver and circulates... 

Diuretics work by increasing the amount of sodium and fluids excreted by the kidneys. Less fluid means less total blood volume and improved circulation and blood pressure. There are five main classes of the drug loop diuretics, thiazide diuretics, potassium-sparing diuretics, osmotic diuretics, and carbonic anhydrase inhibitors. 

Ecstasy use is associated with physiological damage to a number of body systems. These include the heart, brain, liver, kidneys, and the body s ability to regulate temperature. Ecstasy increases heart rate and blood pressure, which is especially dangerous for someone with a known or unknown heart condition, but can also cause an irregular heartbeat in an ordinarily healthy person. An irregular heartbeat means the heart pumps less effectively therefore the blood flow to the brain and other organs is not adequate. This condition increases the risk for heart attack, stroke, and other types of heart failure. 

Peripheral vasculature. PGI2, PGE, and PGE2 induce vasodilation in heart, kidney, skeletal muscle, and mesentery, lowering vascular resistance and blood pressure. 

Mineralocorticoids help control the body s water volume and concentration of electrolytes, especially sodium and potassium. Aldosterone acts on kidney tubule cells, causing a reabsorption of sodium, bicarbonate, and water. Conversely, aldosterone decreases reabsorption of potassium, which is then lost in the urine. [Note Elevated aldosterone levels may cause alkalosis and hypokalemia, whereas retention of sodium and water leads to an increase in blood volume and blood pressure (see p. 180). Hyperaldosteronism is treated with spironolactone (see p. 232).]... 

The practice nurse is concerned by Kevin s symptoms, especially since she notices that Kevin s ankles are swollen. She suspects that Kevin has developed a kidney problem. If this is quickly detected and treated, further damage and loss of kidney function may be prevented or at least slowed. Care in the control of blood glucose and blood pressure is very important for diabetic patients and can reduce kidney problems, such as loss of albumin in the urine. Urine and blood samples are taken, with the following results ... 

Maintenance of an adequate oxygen supply is the first priority. A systolic blood pressure of 80 mmHg can be tolerated in a young person but a level below 90 mmHg will imperil the brain or kidney of the elderly. Expansion of the venous capacitance bed is the usual cause of shock in acute poisoning and blood pressure may be restored by placing the patient in the head-down position to encourage venous return to the heart, or by the use of a colloid... 

Suki, W, N, (1988). Dietary potassium and blood pressure. Kidney Inr, Suppi 34(25), S175-S176. 

Aviv A. John E. Bernstein J, Goldsmith Dl, Spitzer A. Lead intoxication during development. Its late effects on renal function and blood pressure. Kidney Int 1980 17 430-443. 

Because control of renal function and blood pressure is multifactorial, the causal contribution of lead is difficult to isolate. A number of biomarkers (blood, tibial, and patella lead), and a variety of populafions differing by age, gender, race, and level of exposure are examined. Systohc and diastolic pressures are assessed separately and may be analyzed both as continuous or dichotomous variables. Kidney function is assessed by the serum creatinine concentration or empirical adjustments of the creatinine to estimate GFR. Large populations are required to achieve statistical significance amidst the noise of the multifactorial causality and the imprecision of outcome measures. Inconsistent results and weak correlations are, therefore, expected as smaller and smaller outcome effects are evaluated. 

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