Atrial natriuretic factor in renal failure and posthemodialytic postural hypotension

Treatment of post-dialytic orthostatic hypotension with an inflatable abdominal band in hemodialysis patients

The purpose of this study was to ascertain whether abdominal compression with an inflatable abdominal band, a device we developed, improved post-dialytic orthostatic hypotension (OH) in hemodialysis (HD) patients. Twenty-five chronic HD patients with intractable post-dialytic OH were recruited. Post-HD changes in systolic blood pressure (DeltaSBP) in the supine and standing positions were compared in the patients, measured with or without the use of the band. The study showed DeltaSBP after HD without the band was significantly greater than that measured before HD (-36.1+/-18.2 vs -13.1+/-16.8 mm Hg; P<0.0001). DeltaSBP after HD with the band was reduced significantly in comparison to DeltaSBP after HD without the band (-19.4+/-21.2 vs -36.1+/-18.2 mm Hg; P<0.002). Use of the band did not cause an elevation in SBP in the supine position (149.0+/-29.6 vs 155.4+/-25.7 mm Hg); however, it did increase SBP upon standing (129.6+/-27.3 vs 117.2+/-22.6 mm Hg; P<0.05). Eight patients in whom an increase in SBP of 25 mm Hg or more was achieved with the band were classified as responders. Ejection fraction was significantly higher (76.4+/-11.1 vs 61.9+/-13.6%; P<0.02) and atrial natriuretic peptide concentration significantly lower (27.9+/-22.0 vs 68.9+/-47.5 pg/ml; P<0.02) in responders than in non-responders. We conclude that the abdominal band was effective for overcoming post-dialytic OH, without elevating supine SBP in some patients.

Natriuretic Peptides in Acute and Chronic Kidney Disease and during Renal Replacement Therapy

Plasma levels of natriuretic peptides are elevated in patients with chronic kidney disease owing to impairment of renal function, hypertension, hypervolemia, and/or concomitant heart disease. Proteinuria and/or immunosuppression also contribute to enhanced plasma levels and increased urinary excretion of natriuretic peptides. Atrial natriuretic peptide (ANP) and particularly brain natriuretic peptide (BNP) levels are linked independently to left ventricular mass and function and predict total and cardiovascular mortality. ANP and BNP decrease significantly during hemodialysis treatment but increase again during the interdialytic interval. Intraperitoneal administration of ANP decreases peritoneal fluid and glucose absorption, as well as lymphatic flow rate. Successful kidney transplant normalizes the plasma levels of natriuretic peptides in the majority of patients. In experimental animals but not in humans, ANP administration protects against ischemic acute renal failure. Since proANP31-67 peptide does not cause hypotension, this vessel dilator may protect the kidney during acute renal failure by intrarenal vasodilation and stimulation of endogenous prostaglandin E2 synthesis.

Relationship of plasma Dendroaspis natriuretic peptide-like immunoreactivity and echocardiographic parameters in chronic haemodialysis patients

BACKGROUND AND AIMS

The Dendroaspis natriuretic peptide (DNP), which was recently isolated from the venom of the green Mamba snake, Dendroaspis angusticeps, is a 38 amino acid peptide containing a 17 amino acid disulfide ring structure. The purpose of this study was to evaluate the effect of haemodialysis (HD) on the plasma concentration of DNP, and to investigate the relationship between the 2-D echocardiographic parameters and the changes in the plasma DNP levels during HD.

METHODS

Forty-five haemodialysis patients and 22 healthy individuals underwent a measurement of plasma DNP-like immunoreactivity, serum creatinine, haematocrit, blood pressure and bodyweight before and after each HD session. Echocardiography was performed before and after HD. The peak early diastolic transmitral flow velocity (E), peak late diastolic transmitral flow velocity (A), and E/A ratio were measured by using a pulsed Doppler echocardiogram.

RESULTS

The plasma DNP-like immunoreactivity of those in the pre-HD state was significantly higher (235.6 +/- 45.8 pg/mL) than those of the healthy subjects (105.3 +/- 31.1 pg/mL). In addition, the plasma DNP-like immunoreactivity was significantly decreased after HD (204.4 +/- 55.4 pg/mL). The left atrial diameter, left ventricular diameter at end diastole and end systol, E velocity, A velocity, E/A ratio and inferior vena cava diameter were significantly decreased after HD. There were significant correlations between the changes of plasma DNP-like immunoreactivity and the changes in the bodyweight and inferior vena cava diameter, respectively.

CONCLUSION

These results suggest that the plasma DNP-like immunoreactivity might be involved in the regulation of the blood volume in patients undergoing HD.

Natriuretic peptides and acute renal failure

Atrial natriuretic peptides (ANPs) are a family of peptide hormones, e.g., ANP, long-acting natriuretic peptide, vessel dilator, and kaliuretic peptide synthesized by the ANP gene. Brain natriuretic peptide (BNP) and C-type natriuretic peptide are also members of this family but are synthesized by separate genes. Within the kidney, the ANP prohormone's posttranslational processing is different from that of other tissues, resulting in an additional four amino acids added to the NH2 terminus of ANP (e.g., urodilatin). Each of these natriuretic and diuretic peptides increases within the circulation with acute renal failure (ARF). Renal transplantation but not hemodialysis returns their circulating concentrations to those of healthy individuals. BNP and adrenomedullin, a 52-amino acid natriuretic peptide, have beneficial effects on glomerular hypertrophy and glomerular injury but do not improve tubular injury (i.e., acute tubular necrosis). Vessel dilator ameliorates acute tubular necrosis with regeneration of the brush borders of proximal tubules. Vessel dilator decreases mortality in ARF from 88 to 14% at day 6 of ARF, even when given 2 days after renal failure has been established.

Plasma concentration of human brain natriuretic peptide in patients on hemodialysis

The plasma concentration of immunoreactive human brain natriuretic peptide (ir-BNP) was measured in 40 patients on hemodialysis (HD) and in 12 healthy subjects. Immunoreactive human atrial natriuretic peptide (ir-ANP) was also measured. The mean (+/- SE) plasma ir-BNP concentration in the patients before HD (18.4 +/- 3.4 fmol/mL) was markedly higher than that in the control group (0.39 +/- 0.08 fmol/mL). The plasma ir-BNP level was significantly decreased by HD from 18.4 +/- 3.4 fmol/mL to 10.5 +/- 2.2 fmol/mL (P < 0.001), but the latter value was still higher than the upper limit of the normal range for our laboratory. There were significant correlations between the plasma ir-ANP level and the mean blood pressure before HD (P < 0.05) and between the HD-induced changes in plasma ir-ANP level and mean blood pressure (P < 0.001). These correlations were not observed between the plasma ir-BNP level and mean blood pressure. The plasma ir-BNP level correlated with the cardiothoracic ratio and this correlation was closer to that between the plasma ir-ANP level and cardiothoracic ratio. Ultrasound echocardiographic studies in 13 patients revealed that the pre-HD state of high cardiac output was correlated by HD in association with decreases in plasma ir-BNP and ir-ANP levels. Correlations were observed between the pre-HD ir-ANP level and the interventricular septal thickness index (r = 0.68, P < 0.05) and between the change in ir-BNP level and that in left atrial diameter (r = 0.806, P < 0.001). In conclusion, BNP levels were high in HD patients compared with the control subjects and were decreased during HD. In addition, BNP and ANP levels correlated with several parameters of volume change and cardiac status.

Atrial natriuretic peptide and circadian blood pressure regulation: clues from a chronobiological approach

A critical review of the data available in the literature today permits a better understanding of the multiple actions of atrial natriuretic peptide (ANP) on the cardiovascular system. Moreover, the results of chronobiological studies suggest a role for this peptide in the determination of the circadian rhythm of blood pressure (BP). ANP can affect BP by several mechanisms, including modification of renal function and vascular tone, counteraction of the renin-angiotensin-aldosterone system, and action on brain regulatory sites. A series of interrelated events may follow from very small changes in the plasma levels of ANP. The endpoints are blood volume and BP reduction, but they are rapidly offset (mainly by reactive sympathetic activation) as soon as blood volume or pressure is threatened. The circadian rhythms of BP and ANP are antiphasic under normal conditions and in essential hypertension. The loss in the nocturnal decrease of BP is accompanied by a comparable loss in the nocturnal surge of ANP in hypertensive renal failure and hypotensive heart failure. In the latter condition, BP and ANP variabilities correlate significantly both before and after therapy-induced functional recovery, independently of the mean BP levels. Autonomic function modulates the secretion of ANP, which seems more apt to determine only transient changes in BP levels, as suggested by the short half-life of the peptide and the buffering role of its clearance receptors. There is now sufficient evidence that ANP contributes to short-term control over BP and electrolyte balance, in contrast and in opposition to the renin-angiotensin-aldosterone system, which is involved primarily in long-term BP control. By interfering with other well-established neurohormonal factors, ANP appears to be an additional modulator of the circadian rhythm of BP.

Plasma levels of vasoactive regulatory peptides in patients receiving regular hemodialysis treatment

The fasting plasma levels of 10 vasoactive regulatory peptides were measured by radioimmunoassay in 23 stable patients with chronic renal failure receiving regular hemodialysis treatment (RDT) and compared with those of healthy controls. The plasma concentrations of arginine vasopressin, atrial natriuretic peptide, beta-endorphin, methionine-enkephalin, motilin, neuropeptide Y, substance P, and vasoactive intestinal peptide were increased. The plasma level of calcitonin gene-related peptide was not statistically different from that of the controls. The plasma concentration of gamma 2-melanocyte-stimulating hormone was lowered in the RDT-patients. The arterial blood pressure correlated with the plasma levels of motilin and neuropeptide Y. We conclude that patients with chronic renal failure receiving RDT have increased concentrations of 8 out of 10 measured vasoactive regulatory peptides. The elevated levels of vasoactive peptides may contribute to the adaptation of the cardiovascular system to impaired renal function.