Acute effect of haemodialysis on serum markers of myocardial damage

Cardiac markers are more likely to be elevated in dialysis patients than in patients with renal failure not on dialysis. In this study, 31 patients (20 males, 11 females) undergoing chronic haemodialysis were enrolled. The effect of haemodialysis on cardiac troponin T (cTnT), I (cTnI), creatine kinase MB (CKMB) mass, CKMB activity and myoglobin assays was assessed by comparing pre- and post-haemodialysis determinations. After correcting for haemoconcentration, significant differences were observed (mean +/- SEM, pre- vs post-dialysis) for myoglobin (178.9 +/- 19.3 vs 225.0 +/- 28.4 ng/ml; p=0.006) for cTnT (0.111 +/- 0.028 vs 0.148 +/- 0.037 ng/ml; p=0.004), for CKMB mass (2.75 +/- 0.37 vs 2.59 +/- 0.37 ng/ml; p=0.000) and CKMB activity (14.8 +/- 0.9 vs 13.1 +/- 0.9 U/l; p=0.000) assays. Our study questions the reliability of cardiac markers in dialysis patients and suggests that the clinical threshold value and diagnostic efficiency of each assay needs to be validated. Although these differences exceeded clinical threshold values in only a few patients, serum markers of myocardial damage in dialysis patients should be interpreted with caution.     

High-performance liquid chromatographic characterization of neurophysins in chronic renal failure

Levels of immunoreactive (IR) oxytocin (OT)-associated or estrogen-stimulated neurophysin (ESN) and vasopressin-associated or nicotine-stimulated neurophysin (NSN) were measured in plasma of patients with chronic renal failure before and after hemodialysis (HD) and intermittent peritoneal dialysis (IPD), and during continuous ambulatory peritoneal dialysis (CAPD). ESN-IR in 17 patients before HD was 24.4 +/- 2.7 ng/ml (mean +/- SEM) and increased after HD to 33.2 +/- 4.1 ng/ml (P less than 0.001). ESN-IR in 17 patients with CAPD was 15.2 +/- 3.4 ng/ml, significantly lower than in patients undergoing HD, P less than 0.001. In patients receiving IPD (n = 6), ESN was 11.6 +/- 3.7 ng/ml and did not change significantly after IPD. Levels of ESN in patients with renal failure were increased compared with levels in normal individuals, 1.0 +/- 0.1 ng/ml. Levels of ESN were not correlated with laboratory parameters that may be abnormal in renal failure. NSN levels in 16 of 17 patients undergoing HD were 3.2 +/- 0.34 ng/ml and in 14 of 17 patients with CAPD were 2.9 +/- 0.4 ng/ml, respectively. ESN before HD (r = 0.63, P less than 0.01), after HD (r = 0.85, P less than 0.001), and in patients with CAPD (r = 0.83, P less than 0.001) and IPD (r = 0.81, P less than 0.05) correlated significantly with an OT-like peptide previously found to be increased in renal failure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Plasma levels of endothelin in chronic renal failure and after renal transplantation: impact on hypertension and cyclosporin A-associated nephrotoxicity.

1. Plasma levels of endothelin were measured in 30 patients with chronic renal failure, 32 patients on chronic haemodialysis treatment and 25 renal graft recipients with stable renal graft function. 2. In patients with chronic renal failure as well as in patients on regular haemodialysis treatment, mean plasma levels of endothelin were significantly increased (4.59 +/- 2.09 pg/ml, 10.08 +/- 3.12 pg/ml, respectively) when compared with normal subjects (1.88 +/- 0.6 pg/ml, P less than 0.01, P less than 0.001, respectively). 3. In the group with chronic renal failure a positive correlation between the plasma level of endothelin and the plasma concentration of creatinine was observed (P less than 0.003). 4. Renal graft recipients on cyclosporin A with stable renal graft function had a normal plasma level of endothelin suggesting that cyclosporin A nephrotoxicity is not mediated by endothelin. 5. Hypertensive patients with chronic renal failure or on regular haemodialysis and hypertensive renal graft recipients did not differ from the corresponding normotensive population with regard to the plasma level of endothelin, demonstrating that an increased plasma level of endothelin does not play a major role in the pathogenesis of renal hypertension.     

Inadequate aldosterone response to hyperkalemia during angiotensin converting enzyme inhibition in chronic renal failure

To assess the mechanism involved in hyperkalemia during angiotensin converting enzyme inhibition with captopril in chronic renal failure, captopril, 150 mg/day, was administered to 16 patients with hypertension with plasma creatinine levels between 1.6 and 12.4 mg/dl. After 4 weeks of therapy, plasma potassium levels increased from 3.9 +/- 0.1 to 5.5 +/- 0.2 mEq/L (P less than 0.001) and the final plasma potassium levels correlated with plasma creatinine levels (r = 0.67; P less than 0.01). In six patients with plasma creatinine levels greater than or equal to 3 mg/dl, aldosterone excretion decreased after 4 weeks of captopril, from 7.5 +/- 3.1 to 1.8 +/- 0.5 micrograms/24 hr, whereas plasma renin activity increased from 0.6 +/- 0.2 to 4.4 +/- 1.1 ng/ml/hr (P less than 0.05). This was associated with increases in plasma potassium levels from 3.9 +/- 0.2 to 5.4 +/- 0.4 mEq/L (P less than 0.005) and a significant reduction in fractional excretion of potassium from an average of 34% to 25%. No significant changes in plasma creatinine levels were observed during therapy. There was a significant positive correlation between aldosterone excretion and the potassium excretion fraction (r = 0.53; P less than 0.01). Increases in plasma potassium levels were not able to increase aldosterone excretion, although the greater the plasma potassium level attained, the smaller the reduction in aldosterone excretion (r = 0.47; P less than 0.05). Our results indicate that adequate aldosterone production is essential to preserve potassium homeostasis in chronic renal failure. Moreover, angiotensin II appears necessary for an adequate aldosterone response to potassium stimulation.     

Plasma concentrations of atrial natriuretic peptide in various diseases

Using a radioimmunoassay for atrial natriuretic peptide (ANP) we studied plasma concentrations of immunoreactive ANP in order to investigate the pathophysiological role of ANP in patients with various diseases. Plasma ANP levels were elevated in patients with congestive heart failure (394 +/- 260 pg/ml, n = 8) and chronic renal failure (219 +/- 86 pg/ml, n = 11). In patients undergoing hemodialysis plasma ANP levels were markedly high and decreased after hemodialysis from 433 +/- 166 pg/ml to 204 +/- 92 pg/ml (n = 11). ANP was removed from blood to dialysate (21 +/- 13 pg/ml of dialysate, n = 6, dialysate flow: 500 ml/min). Plasma ANP level was conversely correlated with creatinine clearance (r = -0.812, p less than 0.001) in patients with renal diseases (n = 29). In patients with atrial fibrillation, pace maker implantation, lung disease, chronic glomerulonephritis, nephrotic syndrome, essential hypertension, liver disease and cerebrovascular disease, plasma ANP levels were not significantly different from those in normal subjects (70 +/- 32 pg/ml, n = 28). These results suggest that ANP may be a circulating hormone playing pathophysiological roles in congestive heart failure and chronic renal failure.     

Immunoreactive N-terminal pro-atrial natriuretic peptide in human plasma: plasma levels and comparisons with alpha-human atrial natriuretic peptide in normal subjects, patients with essential hypertension, cardiac transplant and chronic renal failure

1. Plasma levels of immunoreactive N-terminal pro-atrial natriuretic peptide (N-terminal ANP) have been measured in 25 normal subjects, 29 patients with essential hypertension, six cardiac transplant recipients, seven patients with dialysis-independent chronic renal failure and 11 patients with haemodialysis-dependent chronic renal failure. Plasma was extracted on Sep-Pak cartridges and N-terminal ANP immunoreactivity was measured using an antibody directed against pro-ANP (1-30). 2. Plasma levels of N-terminal ANP (means +/- SEM) were 235.3 +/- 19.2 pg/ml in normal subjects and were significantly raised in patients with essential hypertension (363.6 +/- 36.3 pg/ml), in cardiac transplant recipients (1240.0 +/- 196.2 pg/ml), in patients with chronic renal failure not requiring dialysis (1636.6 +/- 488.4 pg/ml) and patients with chronic renal failure on maintenance haemodialysis (10336.1 +/- 2043.7 pg/ml). 3. There were positive and significant correlations between the plasma levels of N-terminal ANP and alpha-human ANP (alpha-hANP) with individual correlation coefficients of 0.68 within the normal subjects, 0.47 in patients with essential hypertension, 0.78 in patients with dialysis-independent chronic renal failure and 0.68 in patients with haemodialysis-dependent chronic renal failure (P less than 0.05 in every case).(ABSTRACT TRUNCATED AT 250 WORDS)     

Nizatidine disposition in subjects with normal and impaired renal function

To test the hypothesis that renal insufficiency alters nizatidine disposition, we determined the pharmacokinetics of nizatidine and its major metabolite after a single oral dose in normal volunteers and patients with various degrees of renal dysfunction, after a single intravenous dose in normal volunteers and patients with severe renal failure and during hemodialysis. After intravenous administration the elimination half-life increased from 1.5 +/- 0.2 hours in normal volunteers to 6.9 +/- 3.3 hours in patients with renal failure. The plasma clearance decreased from 0.59 +/- 0.07 L/kg/hr in normal volunteers to 0.14 +/- 0.02 L/kg/hr in patients with renal failure. Nizatidine bioavailability was nearly 100% in normal volunteers but decreased to 75% in patients with renal failure. The volume of distribution was 1.3 +/- 0.1 L/kg in normal volunteers and was not different in patients with renal failure. Nizatidine protein binding was about 30% in normal and uremic plasma. The drug was not substantially removed by hemodialysis. Patients with creatinine clearances less than 50 ml/min/1.73 m2 should receive 150 mg nizatidine once each evening. Patients with creatinine clearances less than 20 ml/min/1.73 m2 should receive 150 mg nizatidine every other night.     

Renal excretion of antidiuretic hormone in healthy subjects and patients with renal failure

Urinary clearance of antidiuretic hormone (ADH) has been measured under basal conditions and during intravenous administration of arginine vasopressin in ten healthy subjects, and only under basal conditions in 18 patients with chronic renal failure and seven patients with acute renal failure at the polyuric phase of the disease. In healthy subjects studied under conditions of mild water diuresis plasma concentration, urinary excretion rate, urinary clearance and fractional clearance of ADH were 3.3 +/- 0.36 pg/ml, 25.2 +/- 5.5 pg/min, 7.5 +/- 1.2 ml/min and 6.4 +/- 1.0% (means +/- SEM) respectively. When plasma ADH was raised to levels between 7 and 26 pg/ml during intravenous administration of the hormone, urinary excretion rate and urinary clearance of ADH increased. Tubular reabsorption of ADH did not reach a plateau but progressively increased in the range of plasma ADH studied. In patients with chronic renal failure, plasma concentration, urinary excretion rate, urinary clearance and fractional clearance of ADH were 2.8 +/- 0.19 pg/ml, 9.4 +/- 2.0 pg/min, 3.4 +/- 0.6 ml/min and 10.0 +/- 2.9% (means +/- SEM) respectively. Urinary excretion rate and urinary clearance were significantly lower than in healthy subjects. In patients with acute renal failure, plasma concentration, urinary excretion rate, urinary clearance and fractional clearance of ADH were 4.6 +/- 0.47 pg/ml, 52.8 +/- 15.8 pg/min, 9.5 +/- 2.7 ml/min and 24.9 +/- 4.4% (means +/- SEM) respectively. Urinary excretion rate and fractional clearance were higher than in healthy subjects and patients with chronic renal failure.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of hemodialysis on traditional and innovative cardiac markers

The diagnostic approach to acute coronary syndrome (ACS) is challenging in patients with impaired renal function since most serum biomarkers are commonly increased in this clinical setting. Cardiac troponin T (cTnT), creatine kinase isoenzyme MB (CK MB), myoglobin, and ischemia modified albumin (IMA), were assayed in 45 patients prehemodialysis (pre-HD) and posthemodialysis (post-HD), and results were adjusted for hemoconcentration. The pre-HD values of serum IMA and cTnT were above the respective diagnostic thresholds (IMA<85 K units/L; cTnT <0.03 ng/mL) in six (13%) and 27 (60%) patients undergoing chronic HD, respectively. A significant (105.0 vs. 79.0 K units/L, P<0.0001) and variable (+38%; 95% confidence interval [CI], 12-65%) increase of serum IMA was observed post-HD, whereas the other biomarkers significantly decreased (cTnT: 0.029 vs. 0.044 ng/mL, P=0.016; CK-MB: 2.33 vs. 2.50 microg/L, P<0.0001; myoglobin: 128.1 vs. 148.7 microg/L, P<0.0001). Biomarkers of myocardial injury, especially cTnT and IMA, might be used in HD patients, provided that an appropriate diagnostic interpretation is guarantee, according to individual baseine value, metabolism, and time of sampling. Moreover, IMA might be reliably applied to stratify the long-term risk of these patients, but not for diagnosing an ACS during or immediately post-HD.     

Prevalence, causes and effects of increased iron storage in patients with kidney transplantation

Patients on chronic hemodialysis often need blood transfusions due to erythropoietin deficiency. Even after successful kidney transplantation iron overload may persist. Former histological studies have revealed siderosis of the liver in 69% of all patients whose serum ferritin was above 1100 ng/ml. The aim of the present study was to evaluate the influence of iron overload on liver function. In 146 symptom free patients with renal allografts serum ferritin was determined to detect possible iron overload. Serum ferritin between 4 and 5480 ng/ml were found (women: 358.7 +/- 105.3; men 282.4 +/- 63.3 ng/ml; x +/- SEM). Twelve patients (8.1%) had ferritin levels higher than 1100 ng/ml. These twelve patients as well as another group of eight patients with renal allografts whose serum ferritin was known to be higher than 1100 ng/ml were included for further evaluation. Their data were matched and compared with those of a control group also patients with renal allograft (same age and sex) whose serum ferritin was lower than 1100 ng/ml. Transaminases (SGPT 22.6 +/- 3.6 vs. 15.4 +/- 6.0 U/l; SGOT 14.7 +/- 2.0 vs. 13.0 +/- 4.8 U/l) and plasma glucose (90.5 +/- 7.1 vs. 76.8 +/- 3.7 mg/dl) were found to be significantly higher (p less than 0.05) in patients with serum ferritin levels above 1100 ng/ml. Elevated transaminases were significantly more frequent in patients with high serum ferritin (9 vs. 2; p less than 0.02) as compared with the control. Ferritin levels significantly correlated with the number of preceding blood transfusions (p less than 0.002). Hbs-persistence was detected in six out of 20 patients with high ferritin levels but only in one out of 20 in the control group (p less than 0.05) whereas anti-Hbs prevalence was not different in the two groups. These data indicate that chronic iron overload should be considered as a possible cause of chronic liver disease in patients with renal allografts.     

Detection of cardiac-specific creatine kinase isoenzyme in sera with normal or slightly increased total creatine kinase activity.

We describe a spectrophotometric kinetic assay for detecting creatine kinase MB isoenzyme activity in the 1 to 10 U/liter range. The MB isoenzyme was isolated [Clin. Chem. 20, 36 (1974)] and assayed (Rosalki method) with an Abbott ABA-100. Good reproducibility was demonstrated for MB isoenzyme activities near 1 U/liter (CV = 2.6%). Sera with normal or slightly increased total creatine kinase activity were evaluated. Sera of 14 patients with acute myocardial infarction contained, per liter, 84 to 236 U of total creatine kinase activity and 4.6 to 28.0 U of isoenzyme MB activity; corresponding ranges for sera from healthy lab technicians and patients with noncardiac disease were 36 to 277 and 0 to 2.6 U. MB isoenzyme activity for infarction patients rose and fell sharply within three days after the infarction. Atypical time-course patterns, MB isoenzyme activity remaining abnormally great for five days, were observed in serum from patients with prolonged atrial fibrillation and congestive heart failure or cardiomyopathy; the BB isoenzyme (1 to 5 U/liter) was also detected in sera of such patients but was absent in sera from infarcation patients. Quantification of column-isolated MB by the assay described is rapid, easy, specific, and extremely sensitive for measuring MB in the 1 to 10 U/liter range.     

Increased plasma histamine levels in uraemic pruritus

1. We determined plasma levels of histamine in uraemic patients and examined their correlation with the presence of pruritus. 2. In 27 patients with chronic renal failure, plasma histamine levels were analysed by radioimmunoassay and were compared with those of 40 healthy adult subjects. The control population showed plasma histamine concentrations of 185 +/- 33 pg/ml, which were significantly lower than those of the patients with renal insufficiency. The highest levels (552 +/- 116 pg of histamine/ml) were found in 16 patients with chronic renal failure (mean serum creatinine 5.1 +/- 1.0 mg/dl) and severe itching. 3. Twelve patients with pronounced pruritus who were on maintenance haemodialysis (serum creatinine 9.2 +/- 1.2 mg/dl) had a mean plasma histamine concentration of 515 +/- 81 pg/ml. Fifteen patients on regular haemodialysis (serum creatinine 9.0 +/- 1.5 mg/dl) and who experienced itching had plasma histamine levels (322 +/- 40 pg/ml) which were significantly lower (P less than 0.01) than those of the patients with pruritus but which were elevated compared with those of the control population (P less than 0.01). 4. No correlation could be found between increased plasma histamine levels and the type of dialysis membrane used or the method of sterilization of the membrane. 5. Haemodialysis alone did not reduce plasma histamine concentrations, although high concentrations could be detected in the ultrafiltrate. In six patients a rapid decrease in plasma histamine concentration from 565 +/- 134 pg/ml to within the normal range could be detected after 60 min of combined haemodialysis and haemoperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pharmacokinetics of the somatostatin analog lanreotide in patients with severe chronic renal insufficiency

OBJECTIVE: To characterize the pharmacokinetic profile of the somatostatin analog lanreotide in patients with severe chronic renal insufficiency. METHODS: Lanreotide was administered by intravenous bolus (7 microg/kg) to 12 patients with severe chronic renal insufficiency and to 12 healthy subjects. Lanreotide serum levels were determined by a radioimmunoassay procedure from time 0 until 24 hours after the administration. The main pharmacokinetic parameters were estimated by a noncompartmental treatment of data. RESULTS: The total serum clearance of lanreotide was found to be significantly lower in patients with severe chronic renal insufficiency than in healthy subjects (mean +/- SEM values of 0.138 +/- 0.017 L/hr/kg versus 0.244 +/- 0.027 L/hr/kg; P < .005). The initial lanreotide concentration, the elimination half-life, the area under the curve from time zero to 24 hours, and the area under the curve from time zero to infinity were significantly greater in patients with severe chronic renal insufficiency than in healthy subjects (307.45 +/- 79.19 ng/mL versus 127.18 +/- 22.65 ng/mL [P < .05]; 2.39 +/- 0.33 hours versus 1.32 +/- 0.20 hours [P < .005]; 62.55 +/- 9.73 ng/mL x hr versus 32.09 +/- 3.23 ng/mL x hr [P < .005]; and 62.95 +/- 9.78 ng/mL x hr versus 32.30 +/- 3.23 ng/mL x hr [P < .005], respectively). The initial volume of distribution, but not the volume of distribution at steady state, was significantly lower in patients with severe chronic renal insufficiency (0.040 +/- 0.008 L/kg versus 0.092 +/- 0.020 L/kg [P < .05] and 0.110 +/- 0.018 L/kg versus 0.172 +/- 0.046 L/kg [difference not statistically significant], respectively). The mean residence time was similar in both groups (0.77 +/- 0.06 hours versus 0.65 +/- 0.14 hours [difference not statistically significant]). CONCLUSIONS: A reduction in the total serum clearance and a decrease in the initial volume of distribution of lanreotide were observed in patients with severe chronic renal insufficiency treated with one intravenous bolus dose of 7 microg/kg lanreotide.     

Spurious brain creatine kinase in serum from patients with renal disease.

Creatine kinase isoenzyme I(BB) is generally not detectable in normal serum, and its occurrence in serum has been documented in only a few disease states. In particular, increased activity of this isoenzyme has been reported in association with chronic renal failure, hemodialysis, and renal transplantation. The present study demonstrates that the apparent creatine kinase observed in the serum of such renal patients is an artifact, observed as a result of measuring creatine kinase isoenzymes by fluorescence. Our observations resemble those of McKenzie et al. [Clin. Chim. Acta 70, 333(1976)] concerning an artifact in the fluorometric determination of lactate dehydrogenase isoenzymes in the sera of patients with end-stage renal failure. The artifact binds to albumin, is not a protein, and occurs in some normal sera at very low concentrations. This artifact can be mistakenly identified as isoenzyme I in renal-disease patients if CK isoenzymes are determined fluorometrically.     

Regional blood flow and neurohormonal responses to milrinone in congestive heart failure

We measured systemic hemodynamics, regional blood flow, and neurohormonal parameters in 13 patients with severe chronic congestive heart failure before and after 1 month of therapy with oral milrinone, a bipyridine cardiotonic agent. After milrinone there were significant reductions in pulmonary wedge pressure (27 +/- 2 to 19 +/- 3 mm Hg; P less than 0.02) and systemic vascular resistance (1866 +/- 152 to 1393 +/- 93 dyne X sec/cm5; P less than 0.05) that were associated with increases in cardiac index (1.85 +/- 0.15 to 2.47 +/- 0.20 L/min/m2; P less than 0.02). There was a marked improvement in forearm blood flow (1.98 +/- 0.14 to 3.02 +/- 0.16 ml/min/dl; P less than 0.01) and a reduction in forearm vascular resistance (45 +/- 3 to 30 +/- 3 U; P less than 0.01). Overall there was no significant change in renal blow flow, renal vascular resistance, or glomerular filtration rate. However, there was a heterogeneous response of renal blood flow and glomerular filtration rate, such that both were directly correlated with the magnitude of increase of cardiac index (r = 0.587 [P less than 0.05] and r = 0.721 [P less than 0.01], respectively). After milrinone there were no significant overall or subgroup changes in urinary sodium excretion, blood volume, plasma renin activity, urinary aldosterone levels, plasma or platelet vasopressin levels, or plasma norepinephrine levels. Thus 1 month of therapy with milrinone improves systemic and forearm hemodynamics, but its effects on renal blood flow and function were heterogeneous. These heterogeneous effects on regional blood flow may depend on the relative vasodilator and inotropic effects of milrinone.     

Using troponin T to diagnose acute coronary syndromes

Elevated troponin T is a useful marker for acute myocardial infarction: it is more specific than is elevated creatine kinase MB isoenzyme, and it remains elevated for many days after creatine kinase levels have returned to normal, providing a useful indicator for late presentations. Nevertheless, creatine kinase MB still has many important roles, including providing estimates of infarct size and diagnosing acute myocardial infarction in patients with renal failure. Often, measuring both markers provides additional information. This article provides a diagnostic algorithm for using both markers.     

Plasma beta-thromboglobulin and platelet factor 4 in patients with chronic renal failure and effect of hemodialysis

Significantly increased levels of plasma beta-thromboglobulin (beta-TG) (76.8 +/- 25.5 ng/ml, p less than 0.01) were observed in 24 patients with chronic renal failure (blood urea nitrogen (BUN) greater than 20 mg/100 ml), as compared with normal subjects (13.2 +/- 5.6 ng/ml). The increase in beta-TG was highly correlated with BUN (r = 0.651, p less than 0.01), creatinine (r = 0.778, p less than 0.01) and creatinine clearance ( t = -0.723, p less than 0.01). Plasma platelet factor 4 (PF4) and normal 5.0 +/- 2.0 ng/ml) also increased significantly to 8.5 +/- 3.4 ng/ml (p less than 0.01). However, statistical correlation between beta-TG and PF4 was not found in these patients. The reason is thought to be due to differences in molecular weight (PF4 8,000 MW; beta-TG 36,000 MW) and half-life time (PF4 30 min; beta-TG 100 min), and due to the difficulty in calculating statistically the correlation because of the narrow distribution of PF4 levels. The high levels of beta-TG (89.4 +/- 3.4 ng/ml) showed a further increase (109.4 +/- 5.8 ng/100 ml, p less than 0.01) after dialysis. This is thought to be due to hemoconcentration, because other blood factors such as RBC, WBC, platelets, fibrinogen, etc were elevated by about 20% during hemodialysis and because no adhesion of platelets to the cellulose membrane did occur. The increase in PF4 levels at 15 min (55.2 +/- 19.6 ng/ml, p less than 0.01) and 1 hr (23.7 +/- 8.4 ng/ml, p less than 0.01) of hemodialysis from the level before it (7.7 +/- 1.3 ng/ml) is thought to be caused the effect of heparin infusion. The change in PF4 was not accompanied by the change in beta-TG. During hemodialysis the decrease of other platelet functions such as adhesiveness, aggregation induced by ADP, collagen and PF3 remained unchanged.     

Quantitation of creatine kinase isoenzymes in human tissues and sera by an immunological method

Antisera against the crystallized creatine kinase isoenzymes from human skeletal muscle (MM) and from human brain (BB) were produced in rabbits. Both the MM and BB isoenzymes were precipitated quantitatively by their homologous antisera. No cross-reaction was observed. The hybrid MB from human heart muscle could not be precipitated completely by either of the two antisera. In artifical mixtures the concentrations of individual creatine kinase isoenzymes were determined from the percentage of non-precipitable activity in the supernatant after reaction with each of the antisera.This immunotitration assay was applied to study the quantitative distribution of creatine kinase isoenzymes in extracts of human tissues. The isoenzyme patterns obtained were compared with those determined by electrophoretic analysis.In sera of patients with myocardial infarction, the immunotitration assay allowed the sensitive and rapid quantitation of creatine kinase isoenzymes, especially of the “infarct-specific” hybrid MB, even in sera with low total activity. This indicates that the method is of diagnostic value.     

Is skeletal response to parathyroid hormone abnormal in experimental renal failure?

It is widely believed that skeletal resistance is the mechanism of impaired calcemic response to parathyroid hormone (PTH) in renal failure. The action of PTH not only involves skeletal mobilization of Ca, it may also stimulate intestinal absorption of Ca and renal conservation of Ca. We have examined each of these factors and studied the calcemic response to PTH in renal failure. PTH, 3 U/hr/100 gm, was infused for 5 hours in rats with renal failure 3 weeks after a five-sixths nephrectomy. In nonfasted animals, the post-PTH increments of total plasma Ca (0.71 +/- 0.06 mg/dl) and ionized Ca (0.37 +/- 0.06 mg/dl) of control sham-operated rats were significantly greater than those of rats with renal failure (plasma Ca 0.37 +/- 0.02 mg/dl and plasma ionized Ca 0.17 +/- 0.01 mg/dl both p less than 0.001). Urinary Ca excretion rate remained unchanged during PTH infusion despite the increase in plasma Ca. Plasma levels of calcitriol after PTH injection were higher in control rats (257 +/- 18 pg/ml) than in rats with renal failure (162 +/- 5 pg/ml, p less than 0.001). Pretreatment of rats with renal failure with 50 ng calcitriol intravenously corrected the abnormal calcemic response to PTH. To exclude the PTH effect on intestinal Ca absorption, PTH infusion was carried out in animals fasted for 18 hours. The post-PTH increments of Ca were no longer different between rats with renal failure (plasma Ca 0.37 +/- 0.04 mg/dl, plasma ionized Ca 0.20 +/- 0.01 mg/dl) and control rats (plasma Ca 0.37 +/- 0.03 mg/dl, plasma ionized Ca 0.19 +/- 0.01), suggesting that skeletal mobilization of Ca was similar between the two groups of animals. We conclude that lack of intestinal response to PTH rather than skeletal resistance was the mechanism of impaired calcemic response to PTH in this model of renal failure.     

Allantoin as a marker of oxidative stress in human erythrocytes

Abstract Background: Uric acid is the final product of purine metabolism in humans. It was determined that this compound has important antioxidative properties and it may be oxidized to allantoin by various reactive oxygen species. Therefore, the measurement of allantoin may be useful for the determination of oxidative stress in humans. Methods: We measured allantoin and uric acid in human plasma and erythrocytes obtained from patients with chronic renal failure before hemodialysis (n=30) and blood donors (n=30). We used a method based on selective isolation of allantoin from deproteinized plasma and erythrocyte lysate samples on AG 1-X8 resin and its derivatization to glyoxylate-2, 4-dinitrophenylhydrazone. Separation of glyoxylate-2, 4-dinitrophenylhydrazone from interfering substances was achieved on reversed phase HPLC with gradient elution and UV/VIS detection at 360 nm. Uric acid was determined by reversed phase HPLC with UV/VIS detection at 292 nm. Results: We found significant differences in allantoin and uric acid concentration between the patients with chronic renal failure and the control group both in plasma (20.5+/-6.5 mumol/L and 323.9+/-62.9 mumol/L vs. 2.1+/-1.1 mumol/L and 270.1+/-62.3 mumol/L, p<0.05) and erythrocytes [82.8+/-39.1 nmol/g hemoglobin (Hb) and 110.7+/-28.8 nmol/g Hb vs. 20.1+/-6.1 nmol/g Hb and 82.1+/-23.7 nmol/g Hb, p<0.05]. Conclusions: Significant higher levels of allantoin in both plasma and erythrocytes of patients with chronic renal failure indicate that allantoin may be used as a good marker of oxidative stress. Clin Chem Lab Med 2008;46:1270-4.