Dynamic renal function testing by compartmental analysis: assessment of renal functional reserve in essential hypertension

Beneficial effects of brief early life angiotensin-converting enzyme inhibition wane with time in sheep with solitary functioning kidney

A child with a congenital solitary functioning kidney (SFK) may develop kidney disease from early in life due to hyperfiltration injury. Previously, we showed in a sheep model of SFK that brief angiotensin-converting enzyme inhibition (ACEi) early in life is reno-protective and increases renal functional reserve (RFR) at 8 months of age. Here we investigated the long-term effects of brief early ACEi in SFK sheep out to 20 months of age. At 100 days gestation (term = 150 days) SFK was induced by fetal unilateral nephrectomy, or sham surgery was performed (controls). SFK lambs received enalapril (SFK+ACEi; 0.5 mg/kg, once daily, orally) or vehicle (SFK) from 4 to 8 weeks of age. At 8, 14 and 20 months of age urinary albumin excretion was measured. At 20 months of age, we examined basal kidney function and RFR via infusion of combined amino acid and dopamine (AA+D). SFK+ACEi resulted in lower albuminuria (∼40%) at 8 months, but not at 14 or 20 months of age compared with vehicle-SFK. At 20 months, basal GFR (∼13%) was lower in SFK+ACEi compared with SFK, but renal blood flow (RBF), renal vascular resistance (RVR) and filtration fraction were similar to SFK. During AA+D, the increase in GFR was similar in SFK+ACEi and SFK animals, but the increase in RBF was greater (∼46%) in SFK+ACEi than SFK animals. Brief ACEi in SFK delayed kidney disease in the short-term but these effects were not sustained long-term.

The roles of protein load test in quantitatively evaluating renal function after severe unilateral ureteral obstruction in adult rabbits

Background

The accuracy of dynamic renal scintigraphy in evaluating the function of hydronephrotic kidneys is controversial. This study sought to investigate the effects of ureteral obstruction on renal function and the role of the protein load test (PLT) in evaluating hydronephrotic kidneys' function.

Methods

A ureteral obstruction model was generated with New Zealand white rabbits. The baseline glomerular filtration rate (GFR) and the GFR during the PLT were measured by dynamic renal scintigraphy at weeks 6, 9, and 12 after obstruction and the renal reserve GFRs were calculated. The renal GFR differences between different time points and between the PLT and baseline status were compared.

Results

(I) Both the baseline GFRs (t=11.287, P=0.000) and the GFRs during the PLTs (t=16.235, P=0.000) of the hydronephrotic kidneys were significantly lower than those of the contralateral kidneys. (II) The baseline GFRs of the obstructed kidneys were not significantly different 6, 9, and 12 weeks after obstruction (F=0.122, P=0.887), but their net reserve GFRs (F=8.419, P=0.004) and relative reserve GFRs (F=3.770, P=0.049) gradually decreased over time. (III) There was no significant correlation between the net reserve GFRs (r=-0.006, P=0.977) or the relative reserve functions (r=-0.022, P=0.920) of the obstructed kidneys and their baseline GFRs. However, there was a significant negative correlation between the net reserve GFRs (r=-0.590, P=0.002) or the relative reserve functions (r=-0.546, P=0.006) of the obstructed kidneys and the duration of obstruction. (IV) The reserve GFRs of the obstructed kidneys were not proportional to their baseline GFRs.

Conclusions

The functional changes in hydronephrotic kidneys are not sensitively reflected by baseline GFRs. GFRs during the PLTs and the reserve GFRs play important roles in the early and accurate evaluation of the function of obstructed kidneys.

The Role of Renal Functional Reserve in Predicting Acute Kidney Injury

Renal functional reserve (RFR) is described as the difference between a glomerular filtration rate (GFR) measured at baseline and after protein stimulation. The percent change in GFR after a protein load varies based on differences in experimental conditions, with the use of an oral meat protein stimulus and a creatinine clearance method to quantify GFR showing the greatest RFR. A decline in RFR has been found in numerous patient groups. Recent investigations have suggested that a lower RFR may be associated with an increased risk of acute kidney injury and eventual chronic kidney disease.

Renal Functional Reserve Is Related to the Nondipping Phenotype and to the Exercise Heart Rate Response in Patients with Essential Hypertension and Preserved Renal Function

BACKGROUND

Renal functional reserve (RFR), defined as the difference between stress and resting glomerular filtration rate (GFR), may constitute a diagnostic tool to identify patients at higher risk of developing acute kidney injury or chronic kidney disease. Blunted RFR has been demonstrated in early stages of hypertension and has been attributed to impaired vascular reactivity due to an overactive sympathetic nervous system (SNS).

OBJECTIVE

The purpose of this study was to investigate whether RFR correlates with other phenotypes expressing overactivity of the SNS in patients with essential hypertension and preserved renal function.

METHODS

Thirty-six patients with untreated essential hypertension and a GFR >60 mL/min/1.73 m2 were enrolled. The following parameters were measured: RFR, 24-h ambulatory blood pressure (BP) profile, a treadmill stress test, and an echocardiographic examination. Urine and venous samples were obtained at specific time points for the determination of clinical parameters, and both resting and stress GFR were calculated by using endogenous creatinine clearance for the measurement of RFR after an acute oral protein load (1 g/kg).

RESULTS

Twenty-one patients had a RFR <30 mL/min/1.73 m2 and 15 had a RFR above this cutoff. A nondipping pattern of 24-h BP was significantly more frequent in patients with low RFR (57.1 vs. 25.0%, p < 0.05 for systolic BP and 52.3 vs. 10.0%, p < 0.02 for diastolic BP). Moreover, patients with lower RFR values showed a blunted heart rate (HR) response to exercise during treadmill test (r = 0.439, p < 0.05). None of the echocardiographic parameters differed between the two groups of patients.

CONCLUSIONS

In hypertensive patients with preserved GFR, reduced RFR is related to nondipping BP phenotype as well as to attenuated exercise HR response. Overactivity of the SNS may be a common pathway. Since loss of RFR may represent a risk factor for acute or chronic kidney injury, hypertensive patients with blunted RFR might need a more careful renal follow-up.

Arterial Hypertension as a Risk Factor for Reduced Glomerular Filtration Rate after Living Kidney Donation

Living kidney donation represents the optimal renal replacement therapy, but recent data suggest an increased long-term renal risk for the donor. Here, we evaluated the risk for reduced estimated glomerular filtration rate (eGFR), death, and major cardiovascular events such as nonfatal myocardial infarction or cerebrovascular event including TIA (transient ischemic attack) and stroke in 225 donors, who underwent pre-donation examinations and live donor nephrectomy between 1985 and 2014 at our center. The median follow-up time was 8.7 years (1.0–29.1). In multivariate analysis, age and arterial hypertension at baseline were significantly associated with a higher risk of adverse renal outcomes, such as (1) eGFR <60 mL/min/1.73 m² (age per year: HR (hazard ratio) 1.05, 95% confidence interval (CI) 1.03–1.08, hypertension: HR 2.25, 95% CI 1.22–3.98), (2) eGFR <60 mL/min/1.73 m² and a decrease of ≥40% from baseline (age: HR 1.08, 95% CI 1.03–1.13, hypertension: HR 4.22, 95% CI 1.72–10.36), and (3) eGFR <45 mL/min/1.73 m² (age: HR 1.12, 95% CI 1.05–1.20, hypertension: HR 5.06, 95% CI 1.49–17.22). In addition, eGFR at time of donation (per mL/min/1.73 m²) was associated with a lower risk of (1) eGFR <60 mL/min/1.73 m² (HR 0.98, 95% CI 0.97–1.00) and (2) eGFR <45 mL/min/1.73 m² (HR 0.95, 95% CI 0.90–1.00). Age was the only significant predictor for death or major cardiovascular event (HR 1.08, 95% CI 1.01–1.16). In conclusion, arterial hypertension, lower eGFR, and age at the time of donation are strong predictors for adverse renal outcomes in living kidney donors.

Haemodynamic or metabolic stimulation tests to reveal the renal functional response: requiem or revival?

Renal stimulation tests document the dynamic response of the glomerular filtration rate (GFR) after a single or a combination of stimuli, such as an intravenous infusion of dopamine or amino acids or an oral protein meal. The increment of the GFR above the unstimulated state has formerly been called the renal functional reserve (RFR). Although the concept of a renal reserve capacity has not withstood scientific scrutiny, the literature documenting renal stimulation merits renewed interest. An absent or a blunted response of the GFR after a stimulus indicates lost or diseased nephrons. This information is valuable in preventing, diagnosing and prognosticating acute kidney injury and pregnancy-related renal events as well as chronic kidney disease. However, before renal function testing is universally practiced, some shortcomings must be addressed. First, a common nomenclature should be decided upon. The expression of RFR should be replaced by renal functional response. Second, a simple protocol must be developed and propagated. Third, we suggest designing prospective studies linking a defective stimulatory response to emergence of renal injury biomarkers, to histological or morphological renal abnormalities and to adverse renal outcomes in different renal syndromes.

Use of stress tests in evaluating kidney disease

PURPOSE OF REVIEW

The kidney, like most other organs, has a reserve capacity that can be utilized in times of increased physiologic demand. The ability to quantify this renal reserve function across various parts of the nephron (glomerular and tubular) has been an area of increased investigation over the past several years. In this review, we discuss several techniques that have been developed to interrogate the maximal physiologic capacity of the injured kidney.

RECENT FINDINGS

Although protein loading has been established as an ideal method to investigate glomerular filtration capacity in healthy kidneys, other methods such as the antagonism of the renin-angiotensin-aldosterone system have demonstrated promise as a method to determine underlying glomerular disease in those with acute kidney injury and other comorbidities (e.g., congestive heart failure and chronic kidney disease). The furosemide stress test has been demonstrated to be a useful clinical tool to ascertain tubular integrity in the setting of acute kidney injury.

SUMMARY

Although various methods to interrogate the reserve capacity of the several nephron segments (glomerulus and tubules) have been investigated, none of these techniques have had wide-spread clinical implementation. Further research into acute kidney injury stress testing is warranted.

Renal Stress Testing in the Assessment of Kidney Disease

As part of human evolutionary development, many human organ systems have innate mechanisms to adapt to increased "work demand" or stress. This reserve capacity can be informative and is used commonly in cardiology to assess cardiac function (e.g., treadmill test). Similarly, the kidney possesses reserve capacity, which can be demonstrated in at least 2 of the following renal domains: glomerular and tubular. When appropriate stimulants are used, healthy patients with intact kidneys can significantly increase their glomerular filtration rate and their tubular secretion. This approach has been used to develop diagnostics for the assessment of renal function. This article reviews both glomerular and tubular kidney stress tests and their respective diagnostic utility.

The chronic kidney disease epidemiology collaboration equation combining creatinine and cystatin C accurately assesses renal function in patients with cirrhosis

BACKGROUND

Accurate measurement of renal function in cirrhotic patients is still challenging. To find the best test for the determination of the true glomerular filtration rate (GFR) in cirrhotic patients this study prospectively compared measured (m)GFR, the gold standard, with estimated (e)GFR using equations based on serum levels of creatinine and cystatin C.

METHODS

GFR was measured by sinistrin clearance using the bolus method in 50 patients with cirrhosis (Child Turcotte Pugh score A, B and C) and 24 age-matched healthy subjects as controls. Measured (m)GFR was compared to eGFR using bias, accuracy 10 % and 30 %, as well as correlation coefficients.

RESULTS

Creatinine-based equations generally overestimated GFR in patients with cirrhosis and showed a bias (average difference between mGFR and eGFR) of -40 (CG), -12 (MDRD) and -9 (CKD-EPI-Cr) ml/min/1.73 m(2). Cystatin C-based equations underestimated GFR, especially in patients with Child Turcotte Pugh score C (bias 17 ml/min/1.73 m(2)for CKD-EPI-CysC). Of these equations, the CKD-EPI equation that combines creatinine and cystatin C (CKD-EPI-Cr-CysC) showed a bias of 0.12 ml/min/1.73 m(2) as compared to measured GFR.

CONCLUSIONS

The CKD-EPI equation that combines serum creatinine and cystatin C measurements shows the best performance for accurate estimation of GFR in cirrhosis, especially at advanced stages.

Is renal hyperfiltration protective in chronic kidney disease-stage 1 pregnancies? A step forward unravelling the mystery of the effect of stage 1 chronic kidney disease on pregnancy outcomes

BACKGROUND

The correlation between advanced or proteinuric chronic kidney disease (CKD) and adverse pregnancy outcomes is intuitive, although how early CKD affects pregnancy remains unknown. Glomerular hyperfiltration is a physiological response to pregnancy, correlated with outcomes in hypertension or collagen diseases. The aim of the study was to correlate first trimester hyperfiltration with pregnancy outcomes in stage 1 CKD patients.

METHODS

A historical prospective study was conducted on the database of our Unit, gathering all pregnant CKD patients referred since 1 January 2000. From 383 pregnancies referred in 2000-2013, 75 patients were selected (stage 1 CKD, referred within the 14th gestational week, singleton deliveries, absence of diabetes, hypertension or nephrotic proteinuria at referral, body mass index [BMI] < 30); 267 'low-risk' pregnancies, followed in the same setting, served as controls. Glomerular filtration rate (GFR) was assessed by Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) and dichotomized at 120 mL/min. The odds for Caesarean section, prematurity, need for Neonatal Intensive Care Unit (NICU) were assessed by univariate analysis and logistic regression.

RESULTS

Risk for adverse pregnancy outcomes was not affected by hyperfiltration (univariate OR GFR ≥ 120 mL/min: Caesarean section 1.30 (0.46-3.65); preterm delivery: 0.84 (0.25-2.80)). In contrast, even in these cases with normal kidney function, stage 1 CKD was associated with prematurity (17.3% vs 4.9% P = 0.001), lower birth weight (3027 ± 586 versus 3268 ± 500 P < 0.001) need for NICU (12% vs 1.1% P < 0.001). In the multivariate analysis, the risks were significantly increased by proteinuria and maternal age but not by GFR.

CONCLUSIONS

In pregnant Stage 1 CKD patients, hyperfiltration was not associated with maternal-foetal outcomes, thus suggesting a need to focus attention on qualitative factors, eventually enhanced by age, as vascular stiffness, endothelial damage or oxidative stress.

The Effect of Mammalian Target of Rapamycin Versus Calcineurin Inhibitor-based Immunosuppression on Measured Versus Estimated Glomerular Filtration Rate After Orthotopic Liver Transplantation

INTRODUCTION

Mammalian target of rapamycin (mTOR) inhibitors have been proposed to preserve renal function in patients after orthotopic liver transplantation (OLT) based on estimated glomerular filtration rate (eGFR). The presented study evaluated their effect on renal function in comparison to calcineurin inhibitors (CNIs) defined by measured GFR.

METHODS

Renal function was measured in patients on mTOR-based (n=28) or on CNI-based (n=51) immunosuppression after OLT by performing inulin clearance (IC) as well as eGFR based on the Modification of Diet in Renal Disease (MDRD4) Study and the chronic kidney disease epidermiology (CKD-EPI) formula at baseline, 6, 12, 18, and 24 months. Statistical analysis was performed by using analysis of variance and serial measurement testing.

RESULTS

The MDRD4 and the IC values differed significantly at study inclusion in both groups (mTOR and CNI group, P=0.001), whereas the CKD-EPI and the IC values did not. Estimated GFR by the MDRD4 results declined throughout the study period in patients on CNI and in patients on mTOR (CNI, 81 vs. 61 mL/min/1.73 m(2), P=0.01; 82 vs. 60 mL/min/1.73 m(2), P=0.01), whereas CKD EPI and measured GFR did not change throughout the study period in the CNI.

CONCLUSION

The use of eGFR especially the MDRD-based formula, in OLT patients, leads to incorrect interpretation of their renal function.

Arterial stiffness: an independent determinant of adaptive glomerular hyperfiltration after kidney donation

After kidney donation, the remaining kidney tends to hyperfiltrate, thus limiting the initial loss of renal function. The potential determinants of this adaptive glomerular hyperfiltration (GHF) and specifically the influence of arterial function are poorly known. In 45 normotensive healthy kidney donors [51 ± 10 yr (mean ± SD), 39 females], glomerular filtration rate (GFR) was measured as the clearance of continuously infused (99m)Tc-DTPA and timed urine collections at baseline, i.e., before donation, and 1 yr after donation. GHF was computed as postdonation GFR minus half of baseline GFR. Arterial function was assessed as baseline carotid-femoral pulse wave velocity (PWV) and carotid augmentation index (AIx). After kidney donation, no significant change in blood pressure (BP) was observed, but two subjects developed hypertension. GFR decreased from 107 ± 19 to 73 ± 15 ml·min(-1)·1.73 m(-2), and mean GHF was 20 ± 10 ml·min(-1)·1.73 m(-2). In univariate analysis, GHF was inversely correlated to age (r(2) = 0.24, P = 0.01), baseline PWV (r(2) = 0.23, P = 0.001), and Aix (r(2) = 0.11, P = 0.031). Nevertheless, GHF was not correlated to baseline peripheral or central BP. In multivariate analysis, baseline PWV, but not AIx, remained inversely correlated to GHF, independently of age, baseline mean BP, and GFR (model r(2) = 0.34, P < 0.001). In healthy subjects selected for renal donation, increased arterial stiffness is associated with decreased postdonation compensatory hyperfiltration.

Glomerular filtration rate (GFR) determination via individual kinetics of the inulin-like polyfructosan sinistrin versus creatinine-based population-derived regression formulae

BACKGROUND

In renal patients estimation of GFR is routinely done by means of population-based formulae using serum creatinine levels. For GFR determination in the creatinine-blind regions or in cases of reno-hepatic syndrome as well as in critical cases of live kidney donors individualized measurements of GFR (mGFR) employing the kinetics of exogenous filtration markers such as the inulin-like polyfructosan sinistrin are necessary. The goal of this study is to compare mGFR values with the eGFR values gained by the Modification of Diet in Renal Disease (MDRD4) and Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) formulae.

METHODS

In 170 subjects comprising persons with normal renal function or with various stages of kidney diseases (CKD 1-4) GFR was measured by application of intravenous bolus of sinistrin and assessment of temporal plasma concentration profiles by means of pharmacokinetic methods (mGFR). Comparisons of mGFR with MDRD4- and CKD-EPI-derived eGFR values were performed by means of linear regression and Bland-Altman analyses.

RESULTS

Reasonable agreement of mGFR and eGFR values was observed in patients with poor renal function [GFR below 60 (ml/min)/1.73 m²]. In cases of normal or mildly impaired renal function, GFR determination by MDRD4 or CKD-EPI tends to underestimate GFR. Notably, there is practically no difference between the two eGFR methods.

CONCLUSIONS

For routine purposes or for epidemiological studies in cases of poor renal function eGFR methods are generally reliable. But in creatinine-blind ranges [GFR above 60 (ml/min)/1.73 m²] eGFR values are unreliable and should be replaced by clinically and physiologically suitable methods for mGFR determination.

CONSORT

http://www.consort-statement.org/index.aspx?o=1190.

The assessment of GFR after orthotopic liver transplantation using cystatin C and creatinine-based equations

The measurement of kidney function after orthotopic liver transplantation (OLT) is still a clinical challenge. Cystatin C (CysC) has been proposed as a more accurate marker of renal function than serum creatinine (sCr). The aim of this study was to evaluate sCr- and CysC-based equations including the Chronic kidney disease (CKD)-EPI to determine renal function in liver transplant recipients. CysC and sCr were measured in 49 patients 24 months after OLT. The glomerular filtration rate (GFR) was calculated using the MDRD 4, the Cockroft-Gault, Hoek, Larsson, and the CKD-EPI equations based on sCr and/or CysC. As reference method, inulin clearance (IC) was estimated. Bias, precision, and accuracy of each equation were assessed and compared with respect to IC. Forty-five percent had a GFR < 60 ml/min/1.73 m(2) according to the IC. The Larsson, the Hoek and the CKD-EPI-CysC formula identified the highest percentage of patients with CKD correctly (88%, 88%, and 84%, respectively). The sCr-based equations showed less bias than CysC-based formulas with a similar precision. All CysC-based equations were superior as compared with sCr-based equations in the assessment of renal function in patients with an IC < 60 ml/min/1.73 m(2).

Cystatin C does not detect acute changes in glomerular filtration rate in early diabetic nephropathy

BACKGROUND

The measurement of renal functional reserve (acute change in glomerular filtration rate [GFR] after protein load) allows the detection of sub-clinical renal dysfunction and has prognostic implications in diabetes. Our aim was to test cystatin C as an index of GFR and renal functional reserve.

METHODS

GFR was measured by C(Sinistrin) at baseline and after protein load in 28 diabetic patients with serum creatinine <1.2 mg/dL. The C(Sinistrin) was compared with cystatin C, serum creatinine, creatinine clearance, and Cockcroft-Gault formula.

RESULTS

Baseline C(Sinistrin) ranged from 67-172 mL/min. Regression analysis showed an overall low relationship between C(Sinistrin) and the indirect markers of GFR. The highest correlation with C(Sinistrin) was obtained for cystatin C clearance (R(2) = 0.58, r = 0.76, p < 0.001), the 1/serum cystatin C (R(2) = 0.58, r = 0.76, p < 0.001), and serum cystatin C (R(2) = 0.52, r = 0.72, p < 0.001). Renal functional reserve was preserved in 6 of 28 patients. There was no significant change in cystatin C in response to protein load.

CONCLUSION

Wide variation in baseline GFR emphasizes the need for the early detection of renal dysfunction. Cystatin C correlated best with C(Sinistrin) at baseline, but did not detect renal functional reserve.

Reduced renal reserve and increased cardiac output in adult female sheep uninephrectomized as fetuses

BACKGROUND

Removal of one kidney during the period of nephrogenesis in the sheep leads to offspring with elevated blood pressure and reduced glomerular filtration rate (GFR) at 6 and 12 months of age. The mechanisms underlying the hypertension and the degree of renal impairment are not known.

METHODS

Changes in GFR were measured in response to an infusion of amino acids and cardiac output was measured by thermal dilution in female offspring at 2 years of age in eight control (sham-operated) and seven animals that had been unilaterally nephrectomized at 100 days of gestation.

RESULTS

Animals uninephrectomized as fetuses had significantly higher blood pressure (91 +/- 2 mm Hg) compared to control animals (86 +/- 2 mm Hg) (P < 0.05). Cardiac output was significantly higher in the uninephrectomized group (148 +/- 10 mL/kg/min) compared to the control group (124 +/- 6 mL/kg/min) (P < 0.05). Heart rate and stroke volume were similar in the two groups although both parameters tended to be higher in the uninephrectomized group. Uninephrectomized animals had a lower basal GFR (P < 0.05). An infusion of amino acids caused a significantly different response in GFR in the two groups (P < 0.01 between the groups) with the uninephrectomized animals having significantly lower GFRs during the infusion period.

CONCLUSION

The increased blood pressure observed after fetal uninephrectomy is due to an increase in cardiac output. Thus, formation of a low number of nephrons in utero may predispose an individual to later renal failure and elevated blood pressure.

Direct fluorometric analysis of a newly synthesised fluorescein-labelled marker for glomerular filtration rate

There is an obvious and growing medical need for an accurate determination of kidney function in the diagnosis and management of renal diseases. The glomerular filtration rate (GFR) is the accepted gold standard measurement of kidney function. Several approaches to estimate the GFR are available, but most of them are inconvenient and, therefore, of limited acceptance. A new method of quantification with fluorescein-isothiocyanate (FITC) sinistrin (FS), a novel GFR marker, has been evaluated. The method is based on the fluorescence label of FS and can be performed with a standard fluorometer. To control the interference of protein with the fluorescence signal, a calibration function was developed. The accuracy of the fluorometric method established is comparable to the so-called "gold standard" of enzymatic determination of polyfructosan. Moreover, FS is easy to handle and requires low-cost instruments. Our results demonstrate the potential of the direct fluorometric analysis of the new FITC-labelled marker of being a precise, simple, rapid and cost-effective method for diagnosing disturbed kidney function and monitoring its treatment efficacy. The dramatic decrease in analytical effort will result in a significantly higher acceptability of GFR determination.

Effect of 12-month therapy with omega-3 polyunsaturated acids on glomerular filtration response to dopamine in IgA nephropathy

BACKGROUND

Omega-3 polyunsaturated acids therapy is efficient in primary IgA nephropathy. It is unknown whether doses of omega-3 smaller than those given previously are still effective. The aim of the study was to examine the effect of omega-3 therapy on renal vascular function in relation to proteinuria and urinary excretion of N-acetyl-beta-D-glucosaminidase (NAG).

METHODS

20 IgA patients aged 36.5 +/- 10.77 with creatinine clearance (Cr(cl)) 105.71 +/- 27.3 ml/min and proteinuria 3.31 +/- 2.01 g/24 h were given orally 810 mg EPA and 540 mg DHA daily for 12 months. Before and at the end of the study, 24-hour proteinuria, serum homocysteine, and Cr(cl) were measured. At the same time, renal vascular function was estimated as dopamine-induced glomerular filtration response (DIR). DIR was measured as: two 120-min lasting Cr(cl) (before and during 2 microg/kg b.w./min i.v. dopamine).

RESULTS

The results obtained during follow-up were as follows (baseline vs. after therapy): DIR 14.9 +/- 16.4 vs. 30.3 +/- 14.3% (p < 0.01); urine protein 2.31 +/- 2.01 vs. 1.31 +/- 1.37 g/24 h (p < 0.01); (Cr(cl)) 105.71 +/- 27.3 vs. 103.9 +/- 20.9 ml/min (n.s.); NAG 8.3 +/- 1.8 vs. 6.0 +/- 1.2 U/g(creat) (p < 0.01), and homocysteine 16.2 +/- 3.15 vs. 13.8 +/- 2.6 micromol/l (p < 0.05). The only correlation found was linear correlation between basal DIR and DIR change (r = -0.570; p < 0.010) and basal NAG (r = -0.460; p < 0.50).

CONCLUSIONS

Omega-3 supplementation is associated with the improvement of both renal vascular function and tubule function.

Cardiovascular and renal effects of carvedilol in dogs with heart failure

To determine the acute effects of carvedilol (beta-blocker) on cardiovascular and renal function and its pharmacokinetics in dogs. Fifteen mature mongrel dogs (7-15 kg) of both sexes were used in these experiments. Eight dogs served as controls, and seven dogs served as iatrogenic mitral regurgitation (MR) experimental animals. Carvedilol (0.2, 0.4, and 0.8 mg/kg, P.O.) was administered, and the blood carvedilol concentration was analyzed by reverse-phase high-performance liquid chromatography. The response to isoproterenol or phenylephrine was also evaluated. Isoproterenol (0.025 microg/kg/min) was infused via the saphenous vein for 5 min, and phenylephrine (5 microg/kg) was injected with carvedilol (0.2, 0.4 mg/kg) or placebo for 4 days. The heart rate and arterial blood pressure were measured, and LV fractional shortening was measured by echocardiography. Glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured by intravenous infusion of sodium thiosulfate and sodium para-aminohippurate. Carvedilol (0.2 mg/kg) decreased the heart rate, whereas renal function, arterial blood pressure, and left ventricular contractile function were not affected. Carvedilol (0.4 mg/kg) decreased heart rate, blood pressure, and renal function. The tachycardic response to isoproterenol was significantly diminished for 36 hr by 0.4 mg/kg carvedilol. Carvedilol 0.2 mg/kg inhibited this effect for 24 hr. Thus, it is necessary to titrate the dosage of carvedilol, it should be initiated at less than 0.2 mg/kg and titrated up to 0.4 mg/kg for heart failure dogs.