Acute adaptative changes to unilateral nephrectomy in humans

Renal function is a major predictor of circulating acyl-CoA-binding protein/diazepam-binding inhibitor

Objective

Acyl-CoA-binding protein (ACBP)/diazepam-binding inhibitor has lately been described as an endocrine factor affecting food intake and lipid metabolism. ACBP is dysregulated in catabolic/malnutrition states like sepsis or systemic inflammation. However, regulation of ACBP has not been investigated in conditions with impaired kidney function, so far.

Design/methods

Serum ACBP concentrations were investigated by enzyme-linked immunosorbent assay i) in a cohort of 60 individuals with kidney failure (KF) on chronic haemodialysis and compared to 60 individuals with a preserved kidney function; and ii) in a human model of acute kidney dysfunction (AKD). In addition, mACBP mRNA expression was assessed in two CKD mouse models and in two distinct groups of non-CKD mice. Further, mRNA expression of mACBP was measured in vitro in isolated, differentiated mouse adipocytes - brown and white - after exposure to the uremic agent indoxyl sulfate.

Results

Median [interquartile range] serum ACBP was almost 20-fold increased in KF (514.0 [339.3] µg/l) compared to subjects without KF (26.1 [39.1] µg/l) (p<0.001). eGFR was the most important, inverse predictor of circulating ACBP in multivariate analysis (standardized β=-0.839; p<0.001). Furthermore, AKD increased ACBP concentrations almost 3-fold (p<0.001). Increased ACBP levels were not caused by augmented mACBP mRNA expression in different tissues of CKD mice in vivo or in indoxyl sulfate-treated adipocytes in vitro.

Conclusions

Circulating ACBP inversely associates with renal function, most likely through renal retention of the cytokine. Future studies need to investigate ACBP physiology in malnutrition-related disease states, such as CKD, and to adjust for markers of renal function.

Organ-Specific Monitoring of Solitary Kidney after Living Donation by Using Markers of Glomerular Filtration Rate and Urinary Proteins

BACKGROUND

Effective follow-up after living kidney donation is important for maintaining the renal function of the donor. We investigated whether the estimated glomerular filtration rate (eGFR) and urinary protein and enzyme levels can provide important information regarding the state of the remaining kidney after donor nephrectomy.

METHODS

Seventy-five living donations were included (prospective/retrospective) in the study. The following parameters were measured up to 1 year after donor nephrectomy: serum creatinine and cystatin C as markers of the GFR; the high-molecular-weight urinary proteins as markers of glomerular injury; and the low-molecular-weight urinary proteins and urinary enzymes as markers of tubular function.

RESULTS

One year after kidney donation, the creatinine and cystatin C values were 1.38-fold increased than their initial values, while the eGFR was 32% lower. At that time, 38% of donors had a moderate or high risk of CKD progression. The biochemical urinary glomerular and tubular kidney markers examined showed different behaviors. After a transient increase, the glomerular proteins normalized. Conversely, the detection of low-molecular-weight urinary proteins and enzymes reflected mild tubular damage at the end of the study period.

CONCLUSIONS

Our findings suggest that for the evaluation of mild tubular damage, low-molecular-weight marker proteins should be included in the urine diagnostic of a personalized living kidney donor follow-up.

Compensatory renal hypertrophy following nephrectomy: When and how?

Following surgical removal of one kidney, the other enlarges and increases its function. The mechanism for the sensing of this change and the growth is incompletely understood but begins within days and compensatory renal hypertrophy (CRH) is the dominant contributor to the growth. In many individuals undergoing nephrectomy for cancer or kidney donation this produces a substantial and helpful increase in renal function. Two main mechanisms have been proposed, one in which increased activity by the remaining kidney leads to hypertrophy, the second in which there is release of a kidney specific factor in response to a unilateral nephrectomy that initiates CRH. Whilst multiple growth factors and pathways such as the mTORC pathway have been implicated in experimental studies, their roles and the precise mechanism of CRH are not defined. Unrestrained hypoxia inducible factor activation in renal cancer promotes growth and may play an important role in driving CRH.

Measured Glomerular Filtration Rate After Kidney Donation: No Evidence of Accelerated Decay

BACKGROUND

The rate of measured glomerular filtration rate (GFR) change in kidney donor years after donation has not been adequately addressed. Whether this change is accelerated in the setting of 1 kidney is also understudied.

METHODS

Two hundred fourteen randomly selected donors underwent serial GFR measurements of nonradioactive iohexol. Estimated GFR at each visit was calculated using the Chronic Kidney Disease Epidemiology Collaboration and Modification of Diet in Renal Disease study equations.

RESULTS

Glomerular filtration rate visits were 4.8 ± 1.3 years apart and the second occurring 16.9 ± 9.1 years after donation. Most (97.7%) were white, 60.8% female, and 78.5% were related to their recipient. Most, 84.6%, had a GFR of 60 mL/min per 1.73 m or higher, 14.0% had a GFR between 45 and 60 mL/min per 1.73 m, and 1.4% had a GFR less than 45 mL/min per 1.73 m. Between visits 1 and 2, 56.5% had a GFR decline, 36.0% increase, and in 7.5%, there was no change. Overall, GFR declined at a rate of -0.42 mL/min per 1.73 m per year. Of GFR estimating models, only Chronic Kidney Disease Epidemiology Collaboration-Creatinine equation produced a slope that was steeper than measured GFR.

CONCLUSIONS

Nearly 2 decades postdonation GFR declined at a rate similar to that seen in the general population, and in one third, GFR continues to increase.

Ultrastructural changes and nestin expression accompanying compensatory renal growth after unilateral nephrectomy in adult rats

Background

Several renal disorders affect the glomerular podocytes. Compensatory structural and functional changes have been observed in animals that have undergone unilateral renal ablation. These changes occur as a pliant response to quench the increased functional demand to maintain homeostasis of fluid and solutes. Nestin is an intermediate filament protein present in the glomerular podocytes of the adult kidney and is linked with the maintenance of its foot process structure. Structural changes in the podocytes ultimately restructure the filtration barrier. Very few studies related to the ultrastructural and histopathologic changes of the podocytes are documented. The present study aimed to assess the histopathologic changes at the ultrastructural level in the adapted kidney at different time intervals following unilateral renal ablation in adult rats and its relation with nestin.

Methods

Forty-eight rats were divided into four groups (n=12 in each group). The animals of Group A were control naïve rats, while the group B, group C and group D animals underwent left unilateral nephrectomy and the remaining right kidney was removed on days 10, 20 and 30, respectively. Each group included four sham-operated rats, which were sacrificed at the same time as the naïve rats. Each nephrectomized sample was weighed and its sections were subjected to hematoxylin and eosin examination, transmission electron microscopic study as well as immunostaining using the intermediate filament protein nestin.

Results

No difference was found between the kidney sections from the control group and the sham-operated groups. A significant increase in the weight of the right kidneys was noted in groups B, C and D (P<0.001). The ultrastructural adaptive changes seen in the glomeruli of group B were subsequently reduced in groups C and D. This finding corresponded to a similar pattern of nestin expression in the podocytes, which showed significant increase in group B followed by reduced expression in groups C and D. Histopathologic and transmission electron microscopic evaluation of group B showed signs of kidney injury. On the other hand, group C animals showed markedly reduced renal adaptive changes and similar changes were also noted in group D.

Conclusion

Correlation between nestin expression and the ultrastructural changes confirms that nestin has a role in increasing the mechanical stability of the podocytes in order to enhance their morphologic changes in response to the tensile glomerular capillary wall. However, further studies investigating more remote ultrastructural changes and their relation with nestin expression are needed to confirm this relationship.

Consequences of increasing convection onto patient care and protein removal in hemodialysis

INTRODUCTION

Recent randomised controlled trials suggest that on-line hemodiafiltration (OL-HDF) improves survival, provided that it reaches high convective volumes. However, there is scant information on the feasibility and the consequences of modifying convection volumes in clinics.

METHODS

Twelve stable dialysis patients were treated with high-flux 1.8 m2 polysulphone dialyzers and 4 levels of convection flows (QUF) based on GKD-UF monitoring of the system, for 1 week each. The consequences on dialysis delivery (transmembrane pressure (TMP), number of alarms, % of achieved prescribed convection) and efficacy (mass removal of low and high molecular weight compounds) were analysed.

RESULTS

TMP increased exponentially with QUF (p<0.001 for N >56,000 monitoring values). Beyond 21 L/session, this resulted into frequent TMP alarms requiring nursing staff interventions (mean ± SEM: 10.3 ± 2.2 alarms per session, p<0.001 compared to lower convection volumes). Optimal convection volumes as assessed by GKD-UF-max were 20.6 ± 0.4 L/session, whilst 4 supplementary litres were obtained in the maximum situation (24.5 ± 0.6 L/session) but the proportion of sessions achieving the prescribed convection volume decreased from 94% to only 33% (p<0.001). Convection increased high molecular weight compound removal and shifted the membrane cut-off towards the higher molecular weight range.

CONCLUSIONS

Reaching high convection volumes as recommended by the recent RCTs (> 20L) is feasible by setting an HDF system at its optimal conditions based upon the GKD-UF monitoring. Prescribing higher convection volumes resulted in instability of the system, provoked alarms, was bothersome for the nursing staff and the patients, rarely achieved the prescribed convection volumes and increased removal of high molecular weight compounds, notably albumin.

State-of-the-art nanoplatform-integrated MALDI-MS impacting resolutions in urinary proteomics

Urine proteomics has become a subject of interest, since it has led to a number of breakthroughs in disease diagnostics. Urine contains information not only from the kidney and the urinary tract but also from other organs, thus urinary proteome analysis allows for identification of biomarkers for both urogenital and systemic diseases. The following review gives a brief overview of the analytical techniques that have been in practice for urinary proteomics. MALDI-MS technique and its current application status in this area of clinical research have been discussed. The review comments on the challenges facing the conventional MALDI-MS technique and the upgradation of this technique with the introduction of nanotechnology. This review projects nano-based techniques such as nano-MALDI-MS, surface-assisted laser desorption/ionization, and nanostructure-initiator MS as the platforms that have the potential in trafficking MALDI-MS from the lab to the bedside.

Circulating adipocyte fatty acid binding protein is increased in chronic and acute renal dysfunction

BACKGROUND AND AIMS

The adipokine adipocyte fatty acid binding protein (AFABP) is positively associated with the development of the metabolic syndrome, diabetes mellitus, and cardiovascular disease. We hypothesized that AFABP also increases with deteriorating renal function.

METHODS AND RESULTS

Serum AFABP levels were quantified by enzyme linked immunosorbent assay in 532 patients with chronic kidney disease (CKD) covering the whole spectrum of estimated glomerular filtration rate (eGFR) categories from G1 to G5 (study population 1). Furthermore, AFABP was measured in 32 patients before and within 30 h after elective unilateral nephrectomy, a model of acute kidney dysfunction (AKD) (study population 2). Moreover, circulating AFABP was investigated in rats undergoing bilateral nephrectomy (BNE) as compared to sham-operated animals. Median serum AFABP levels adjusted for age, gender, and body mass index significantly increased with increasing eGFR category (G1: 22.0 μg/l; G2: 34.6 μg/l; G3: 56.7 μg/l; G4: 95.2 μg/l; and G5: 173.9 μg/l). Furthermore, renal dysfunction remained positively associated with AFABP in multivariate analysis in this cohort. In patients undergoing unilateral nephrectomy, AFABP increased significantly after surgery (42.1 μg/l) as compared to pre-surgical values (29.3 μg/l). Furthermore, relative changes of post-to-pre-surgical AFABP levels were independently associated with relative changes of post-to-pre-surgical creatinine concentrations. After BNE in rats, AFABP increased significantly as compared to sham-operated animals.

CONCLUSIONS

We show that AFABP is significantly elevated in CKD and AKD patients. Furthermore, measures of renal function are associated with circulating AFABP. Moreover, animal experiments indicate that AFABP levels strongly depend on renal function.

Serum levels of fibroblast growth factor-21 are increased in chronic and acute renal dysfunction

OBJECTIVE

Fibroblast growth factor (FGF)-21 has recently been introduced as a circulating adipokine which reverses insulin resistance and obesity in rodents. In this study, regulation of FGF-21 in renal dysfunction was elucidated in both chronic kidney disease (CKD) and acute kidney dysfunction (AKD).

STUDY DESIGN AND METHODS

Serum concentrations of total FGF-21 were quantified by enzyme-linked immunosorbent assay in 499 patients with CKD stages 1-5 (study population 1). Furthermore, total FGF-21 was determined before and within 30 h after unilateral nephrectomy, a model of AKD, in 32 patients (study population 2). FGF-21 levels were correlated to anthropometric and biochemical parameters of renal function, glucose and lipid metabolism, as well as inflammation, in both studies.

RESULTS

In study population 1, median [interquartile range] circulating FGF-21 adjusted for age, gender and body mass index was significantly different between CKD stages with highest values detectable in stage 5 (stage 1: 86·4 [132·9]; 2: 206·4 [223·1]; 3: 289·8 [409·3]; 4: 591·3 [789·0]; 5: 1918·1 [4157·0] ng/l). Furthermore, estimated glomerular filtration rate remained a strong independent and negative predictor of FGF-21. In study population 2, FGF-21 increased significantly postsurgically (325·0 [984·0] ng/l) as compared to presurgical values (255·5 [243·0] ng/l). Furthermore, relative changes of FGF-21 were independently and positively predicted by relative changes of creatinine.

CONCLUSIONS

We demonstrate that circulating FGF-21 is increased in both CKD and AKD. Our results suggest renal excretion as a major route for FGF-21 elimination. The pathophysiological significance of these findings needs to be elucidated in more detail.

Vitamin A metabolism is changed in donors after living-kidney transplantation: an observational study

Background

The kidneys are essential for the metabolism of vitamin A (retinol) and its transport proteins retinol-binding protein 4 (RBP4) and transthyretin. Little is known about changes in serum concentration after living donor kidney transplantation (LDKT) as a consequence of unilateral nephrectomy; although an association of these parameters with the risk of cardiovascular diseases and insulin resistance has been suggested. Therefore we analyzed the concentration of retinol, RBP4, apoRBP4 and transthyretin in serum of 20 living-kidney donors and respective recipients at baseline as well as 6 weeks and 6 months after LDKT.

Results

As a consequence of LDKT, the kidney function of recipients was improved while the kidney function of donors was moderately reduced within 6 weeks after LDKT. With regard to vitamin A metabolism, the recipients revealed higher levels of retinol, RBP4, transthyretin and apoRBP4 before LDKT in comparison to donors. After LDKT, the levels of all four parameters decreased in serum of the recipients, while retinol, RBP4 as well as apoRBP4 serum levels of donors increased and remained increased during the follow-up period of 6 months.

Conclusion

LDKT is generally regarded as beneficial for allograft recipients and not particularly detrimental for the donors. However, it could be demonstrated in this study that a moderate reduction of kidney function by unilateral nephrectomy, resulted in an imbalance of components of vitamin A metabolism with a significant increase of retinol and RBP4 and apoRBP4 concentration in serum of donors.

The use of SDS-PAGE scanning of spent dialysate to assess uraemic toxin removal by dialysis

Background. Uraemic toxins in the 8 to 60 kDa molecular weight range have been attracting increasing attention in dialysis therapy. However, there are no available standardized methods to evaluate their removal. Using new filtering membranes, we evaluated SDS–PAGE of spent dialysate to assess cut-off ranges and removal capacities into dialysate, while also measuring classical markers of dialyser function.

Methods. Eighteen dialysis patients were washed out for 2 weeks with FX 100 (Helixone^®), followed by randomization to Xevonta Hi 23 (Amembris^®) or FX dialysers for 2 weeks, then crossed over for an additional 2 weeks, and finally placed on Xenium 210 (Purema^®) for 2 weeks. SDS–PAGE scanning of the removed proteins contained in the spent dialysate was performed during all dialysis sessions. Total mass of urea, creatinine, total proteins, beta 2 microglobulin (β2m), retinol-binding protein (RBP) and albumin were measured. The reduction rates of serum urea, creatinine, β2m, leptin, RBP, alpha 1-antitrypsin, albumin and total proteins were also determined.

Results. SDS–PAGE scanning identified four major protein peaks (10–18, 20–22.5, 23–30 and 60–80 kDa molecular weight) and showed clear differences in the amounts of removed proteins between the dialysers, particularly in the 20–22.5, 23–30 and 60–80 kDa ranges. Total mass of removed β2m, RBP and albumin were in agreement with SDS–PAGE, while serum assays showed differing results.

Conclusions. SDS–PAGE scanning provided a good characterization of protein patterns in the spent dialysate; it extended and agreed with protein determinations and allowed a better assessment of dialyser performance in removing 10 to 80 kDa molecular weight substances. It also identified differences between the three mainly filtrating polysulfone dialysers that were not detected with blood measurements.

Temporal stability of the urinary proteome after kidney transplant: more sensitive than protein composition?

The temporal urinary proteome was examined in 4 groups of individuals in order to determine the temporal stability of diverse individuals with apparently good kidney health. The groups consisted of (1) healthy volunteers at zero time, 1 and 6 months, (2) kidney donors before and after surgery, (3) recipients immediately after surgery, and (4) successful kidney transplant recipients from 1 month to 4 years after transplant. Proteins were detected by reverse phase extraction of urine followed by MALDI-TOF profile and by iTRAQ analysis. Unusual components of the MALDI-TOF profiles found only in transplant subjects occurred at m/ z = 3370, 3441 and 3385 (human neutrophil defensins), 4303, 10350, and 11732 (beta-2 microglobulin, B2M). The peaks at m/ z = 4303 and 11732 were also quite intense among kidney donors following surgery. The peaks at m/ z = 4303 and 10350 in transplant recipients were associated with higher serum creatinine. Several additional proteins detected by iTRAQ were up-regulated in a manner that correlated closely with B2M. Overall, despite large differences between protein composition in different transplant recipients, there was remarkable stability for each individual as detected by either MALDI-TOF or iTRAQ analyses. These results suggested that, within limits, stability of profile components may be as important as protein content for definition of kidney health. Longitudinal study of urinary proteins from kidney recipients may demonstrate instability as a sensitive biomarker of adverse kidney health.

Prélèvement rénal chez le donneur vivant : morbidité et suivi à long terme

OBJECTIVE

To evaluate the morbidity of living donor kidney harvesting and the long-term medical consequences and impact on quality of life (QoL).

MATERIAL AND METHODS

Retrospective analysis of medical and surgical data for 114 living kidney donors in a single teaching hospital between 1977 and 2005. Complications were evaluated in relation to the surgical approach and body mass index (BMI) using a Chi-square test or Fisher's exact test. Changes in renal function (serum creatinine, creatinine clearance), proteinuria and blood pressure (BP) were studied by Student's t test or a Mann-Whitney U or Wilcoxon nonparametric test. Long-term QoL was evaluated by the MOS SF-36 questionnaire and a local questionnaire and was then compared to that of the French general population.

RESULTS

The median follow-up was 63 months. The morbidity of kidney harvesting was significantly correlated with the surgical approach (p = 0.018) and a BMI > or = 25 kg/m2 (p = 0.014). No mortality was observed in this series. A moderate elevation of serum creatinine was observed during follow-up (mean serum creatinine increased from 82.2 micromol/l [+/- 16.3] to 104.5 micromol/l [+/- 19.9]), and mean creatinine clearance decreased from 113.4 ml/min [+/- 27.6] to 76 ml/min [+/- 29.9]. Little impact was observed on proteinuria and BP and QoL was not altered by kidney harvesting.

CONCLUSION

The perioperative complication rate is correlated with BMI and a flank incision. Kidney harvesting lowers glomerular filtration, but clearance remained stable during follow-up. Macroalbuminuria or hypertension may be observed, but their frequency is not higher than in the general population. The QoL of living donors is not altered. Clear information for the general public would allow promotion of living donor transplantation.

Advances in urinary proteome analysis and biomarker discovery

Noninvasive diagnosis of kidney diseases and assessment of the prognosis are still challenges in clinical nephrology. Definition of biomarkers on the basis of proteome analysis, especially of the urine, has advanced recently and may provide new tools to solve those challenges. This article highlights the most promising technological approaches toward deciphering the human proteome and applications of the knowledge in clinical nephrology, with emphasis on the urinary proteome. The data in the current literature indicate that although a thorough investigation of the entire urinary proteome is still a distant goal, clinical applications are already available. Progress in the analysis of human proteome in health and disease will depend more on the standardization of data and availability of suitable bioinformatics and software solutions than on new technological advances. It is predicted that proteomics will play an important role in clinical nephrology in the very near future and that this progress will require interactive dialogue and collaboration between clinicians and analytical specialists.

All-trans-retinoic acid inhibits the development of mesangial proliferative glomerulonephritis in interleukin-6 transgenic mice

All-trans-retinoic acid (ATRA), a vitamin A derivative, was reported to suppress the interleukin-6 (IL-6) production and to downregulate the IL-6 receptor (IL-6R) and/or its signal transducer glycoprotein 130. We investigated the in vivo antinephritic effect of ATRA on IL-6 transgenic mice which had developed mesangial proliferative glomerulonephritis (PGN) as well as its in vitro inhibitory effect on the proliferation of rat mesangial cells. In vivo experiments on IL-6 transgenic mice showed that ATRA administration suppressed proteinuria and hematuria and reduced the IL-6 concentrations; furthermore, histological examination demonstrated that it improved PGN. In vitro experiments using rat mesangial cells demonstrated that ATRA inhibited cell growth in a dose-dependent manner within a range from 10(-4) to 10(-6) M. This inhibition by ATRA was partially counteracted by the addition of IL-6. RT-PCR assay results showed that ATRA also reduced IL-6R, but not the glycoprotein 130 expression in mesangial cells. These findings indicate that, by blocking of the IL-6 function, ATRA may be therapeutically effective in PGN.

Beneficial effect of retinoic acid on the outcome of experimental acute renal failure

BACKGROUND

Retinoic acid (RA) exerts beneficial effects on vascular remodelling and experimental nephritis, and plays a role in kidney development. Pathological changes caused by acute renal failure (ARF) result in high mortality. We determined whether RA ameliorates ARF-induced pathology caused by potassium dichromate (PD).

METHODS

Adult Wistar female rats (210-250 g) were randomly allocated to four groups: (i) an ARF group that received PD [15 mg/kg body weight (bw), single dose subcutaneously]; (ii) a group that received PD plus RA (1 mg/kg bw) beginning at 5 days before PD and that continued for 14 additional days; (iii) a group that received PD plus thyroxine (T(4); 8 micro g/100 g bw) with RA; and (iv) a group that received only the vehicle for PD (saline solution). We evaluated functional, biochemical and morphological characteristics of the kidneys.

RESULTS

PD-induced alterations in serum creatinine, creatinine clearance (C(cr)) and fractional excretion of sodium (FeNa) were less severe when rats received RA. PD increased lipoperoxidation and this alteration was partially blocked by RA. Animals undergoing ARF showed severe histological injury (brush border loss, acidophilia, oedema, pyknosis, karyorhexis, cell detachment and disruption of the basement membrane). These alterations were less severe in RA-treated rats, indicating a protective effect on functional and morphological alterations. Alterations in urinary sediment were reduced by RA. The simultaneous administration of T(4) with RA did not produce additional protection.

CONCLUSION

RA exerted beneficial effects on the duration and severity of renal damage induced by PD in a model of renal failure resembling ARF in humans. The protective effect of RA may be mediated by diminished lipoperoxidative damage.

Effect of unilateral nephrectomy on the pharmacokinetics of amikacin in humans

As unilateral nephrectomy is not a rare surgical procedure, it gives rise to the question whether drugs predominantly eliminated through the urinary tract can be handled effectively by the remaining kidney. Amikacin is predominantly excreted via glomerular filtration with only a small fraction undergoing tubular reabsorption, and can be used as a model drug of glomerular elimination. The study was carried out in 28 subjects, 10 one month and 10 one year after unilateral nephrectomy, as well as in 8 healthy subjects. The pharmacokinetics of amikacin was investigated after a 1-h infusion of 5 mg kg(-1) amikacin. Blood samples were collected for 24 h after the end of infusion. Pharmacokinetic parameters of amikacin were calculated using a one-compartment open model for intravenous administration. Amikacin concentrations were significantly elevated in nephrectomized patients as compared with control subjects, both 1 month and 1 year after the surgery, and were similar at these two time-points following unilateral nephrectomy. Pharmacokinetic parameters of amikacin in patients subjected to unilateral nephrectomy were significantly different from those observed in the control subjects. As compared with the controls, an increase in AUC (area under the serum concentration-time curve) by 81% (P < 0.001) and 63% (P < 0.01) 1 month and 1 year after nephrectomy was observed, respectively. The lambda(z) (elimination rate constant) was reduced by 39% (P < 0.001) after 1 month and by 38% (P < 0.001) 1 year after the operation and t 1/2 was prolonged by 70% (P < 0.001) and by 43% (P < 0.01) at the respective time-points following unilateral nephrectomy. CLT (total body clearance of the drug from plasma) and CL(BW) (clearance per kg body weight) were both significantly decreased in unilaterally nephrectomized subjects in comparison with the controls. CLT and CL(BW) were reduced by 53% (P < 0.001) and 42% (P < 0.01) 1 month after nephrectomy, and by 45% (P<0.001) and 42% (P<0.01) 1 year after the surgery, respectively. No significant differences among studied groups were found in C0 (initial serum drug concentration) and Vd (apparent volume of distribution). The results suggest that unilateral nephrectomy impairs elimination of amikacin, and possibly other drugs predominantly eliminated via glomerular filtration.

Can a transplanted living donor kidney function equivalently to its native partner?

Early renal functional adaptation was examined in 81 haploidentical donor and recipient pairs, as well as long-term stability of glomerular filtration rate (GFR) in 78 recipients. GFR was determined pre- and 1 month postnephrectomy in donors and 1 month post-transplant and yearly thereafter in recipients. Compensatory increase in filtration (CIF) of transplanted and native kidneys was calculated using donor pretransplant GFR: [CIF= (GFR at 1 month/donor prenephrectomy GFR) x 100]. Annual rates of change in GFR were estimated using within-patient linear regression analysis (slopes). Recipients without rejection (n = 62) and their donors had similar early GFR and CIF. Those with acute rejection (n = 19) had significantly lower GFR and CIF than their donors (61 +/- 16 mL/min/1.73 m2 and 57 +/- 14% vs. 75 +/- 11 and 69 +/- 9; p = 0.01 and p < 0.001). Recipients without cyclosporine (n = 52) had 1 month GFR and CIF of 70 +/- 14 and 67 +/- 14 vs. 72 +/- 11 and 69 +/- 11 for their donors. Those with cyclosporine (n = 29) had 1 month GFR and CIF of 64 +/- 14 and 62 +/- 16 vs. 69 +/- 12 and 67 +/- 11 for their donors (p = 0.15 and 0.16). Comparison of median (25th, 75th) rates of change of GFR with and without acute rejection or cyclosporine did not demonstrate significant effects of either on stability of allograft function, although there was a trend towards greater loss of GFR in cyclosporine-treated patients [-1.1 (-2.5, 0.8) vs. 0.0 (-1.8, 1.2) mL/min/1.73 m2/year, p = 0.47]. We conclude that, in the absence of rejection, the transplanted kidney maintains the same capacity for functional adaptation as its native partner. Therapy with cyclosporine does not significantly inhibit early physiological adaptation of renal transplants.

Retinoic acid exacerbates experimental radiation nephropathy

Studies have shown that angiotensin-converting enzyme inhibitors and an angiotensin II receptor blocker can delay, but cannot reverse, the progression of experimentally induced radiation nephropathy. In an effort to find a method for reversing injury, three agents were tested in a rat model of radiation nephropathy. Pirfenidone (a phenyl-pyridone antifibrotic) and thiaproline (an inhibitor of collagen deposition) were not capable of retarding the development of radiation nephropathy. However, all-trans retinoic acid (an anti-inflammatory agent) exacerbated radiation nephropathy. We speculated that the detrimental effects of retinoic acid might be the result of stimulation of renal cell proliferation. However, retinoic acid had no effect on tubular or glomerular cell proliferation in normal animals and did not enhance radiation-induced proliferation. A recent report that retinoic acids inhibit nitric oxide production suggested an alternative mechanism, since inhibition of production of nitric oxide is known to exacerbate radiation nephropathy. Experiments demonstrated that retinoic acid exacerbated the radiation-induced drop in renal production of nitric oxide, suggesting that the detrimental effect of all-trans retinoic acid might be explained by inhibition of renal nitric oxide activity. Particularly in view of the recent clinical report of enhancement of radiation nephropathy by retinoic acid in patients receiving bone marrow transplantation, the combination of retinoic acid and renal irradiation should be carried out with great caution.

Prediction of post-operative glomerular filtration rate after nephrectomy for renal malignancy

The importance of a correct estimation of contralateral renal function in cases of renal malignancy is obvious, necessitating a conservative approach to tumour resection when function of the contralateral kidney is markedly reduced. The aim of the present study was to determine the accuracy of preoperative gamma camera renography and (51)Cr-EDTA clearance to predict the glomerular filtration rate (GFR) early and up to 6 months after nephrectomy for renal malignancy. Patients (n=40) underwent both gamma camera renography ((99m)TC-DTPA) and (51)Cr-EDTA clearance preoperatively, whereas (51)Cr-EDTA clearance was measured within 1 week and up to 6 months after nephrectomy. The single kidney GFR values of the contralateral kidneys were estimated preoperatively and then compared with the post-operative (51)Cr-EDTA clearance values. The predicted GFR values were lower compared with the measured post-operative (51)Cr-EDTA clearance values (45 +/- 2 vs. 54 +/- 3 ml min(-1) 1 week after nephrectomy and 53 +/- 3 ml min(-1) 6 months later, P<0.01, respectively). The difference between the measured and predicted GFR was larger in patients below the median age of 60 years (P<0.05) and confined to patients with a relative uptake of >30% by the tumour affected kidney. Prediction of post-operative GFR by non-invasive renal function tests performed prior to surgery for renal malignancy underestimate post-operative GFR when the function of the tumour affected kidney is preserved, indicating an adaptive GFR increase in these cases.

Effects of diet and aging on renal measurements in uninephrectomized geriatric bitches

Under controlled, but varied dietary conditions among geriatric, uninephrectomized Beagle bitches (dogs) observed for 4 years, renal size increase as assessed radiographically and ultrasonographically occurred at variable rates, but on a seemingly continuous basis. The maximum observed mean renal linear parameter increase found was approximately 15%. However, a 10 and 15% increase is a more representative expectation among the 4 parameters (sonographic length, radiographic length, sonographic width, radiographic width) under consideration. The rate of renal size increase was rapid during the first 2 to 3 months following uninephrectomy. Thereafter, the rate of increase was slow, but occurred to varying degrees in both the length and width as assessed radiographically or ultrasonographically. The mechanism creating the size change was hypertrophy, not hyperplasia. Within limits of the 3 diets used in the study, no significant diet effect was found on the rate or degree of long term compensatory hypertrophy. Radiographically and ultrasonographically measured renal length had the greatest correlation with each other as well as with post mortem measurements and are, therefore, the recommended parameter for imaging assessment of compensatory hypertrophy. When the prenephrectomy, radiographic renal lengths and widths were normalized as a ratio of the second lumbar vertebral body length (L2) measured from ventrodorsal radiographs, the diet group means across dogs (approximately three L2 lengths for renal length; two L2 lengths for renal width) were in the middle of the respective previously published normal radiographic ranges for mature dogs (e.g. 2.5 L2 < or = length < or = 3.5 L2; 1.58 L2 < or = width < or = 2.38 L2 lengths). Even after the hypertrophic changes occurred, the radiographic group mean lengths and widths across dogs were still within the specified normal ranges, although toward the upper end of the respective range. This information provides background for clinical interpretation of potential compensatory hypertrophy that may be encountered following uninephrectomy for spontaneous disease in aged dogs. In addition, it appears that available radiographic renal linear ranges for normal mature dogs are applicable to geriatric dogs as well.

Pathophysiology and management of progressive renal disease

Recently, the hypothesis that all renal diseases are inherently progressive and self-perpetuating has focused attention on adaptive changes in renal structure and function that occur whenever renal function is reduced. These glomerular adaptations to renal disease include increases in filtration rate, capillary pressure and size, and are referred to as glomerular hyperfiltration, glomerular hypertension and glomerular hypertrophy, respectively. Extrarenal changes, such as dietary phosphate excess, systemic hypertension, hyperlipidaemia, acidosis and hyperparathyroidism occur in animals with renal disease and may be contributors to progression of renal disease. Emphasis in the management of companion animals with renal disease has shifted to identifying, understanding and controlling those processes that play a role in the progression from early to end-stage renal failure. Advances made by veterinary nephrologists in the past 15 years permit resolution of old controversies, formulation of new hypotheses and discussion of unresolved issues about the nature of progressive renal disease in dogs and cats.

Acute ureteral obstruction and glomerulotubular function in rats

Urinary tract obstruction is a common cause of acute renal failure (ARF). During unilateral ureteral obstruction (UUO) arteriolar vasoconstriction, increase in tubular pressure, and ultrafiltrate retrodiffusion occur. We studied renal function of rats with surgical UUO for 24 hr. After this period of UUO, the contralateral kidney was removed and the right ureter was deobstructed. The control uninephrectomized group consisted of normal rats submitted to left uninephrectomy (UNx). Functional studies were performed 12 and 24 hr, and 7 days after deobstruction and UNx. We measured creatinine clearance, and fractional excretion of sodium and lithium. Using conventional formulas we calculated fractional proximal and distal sodium reabsorption. Initially we observed a reduction in glomerular filtration rate (GFR) after deobstruction (12 and 24 hr). However, after 7 days, the GFR was significantly higher in deobstructed rats than in controls (340.3 +/- 18.3 vs. 286.4 +/- 9.3 microL/min/100 g, p < 0.01). The dry kidney weight was also increased in these rats. The fractional sodium excretion was increased in deobstructed rats, mainly in early studies (12 and 24 hr). Whereas fractional proximal reabsorption was reduced in both groups, the fractional distal reabsorption was significantly decreased in the deobstructed group compared to UNX controls (93.9 +/- 0.9 vs. 98.9 +/- 0.1% after 24 hr, p < 0.01). Our data showed that UUO influenced both glomerular and tubular functions. A salient finding was the overcorrection of GFR 7 days after deobstruction. The renal release of hormones and growth factors could mediate these alterations in renal function through their vascular, tubular, and proliferative actions.

Beta 2 microglobulin isoforms in healthy individuals and in amyloid deposits

beta 2 microglobulin (beta 2m) is classically known to have isoforms with isoelectric points (pI) 5.7 and 5.3. New isoforms of beta 2m with lower pI, probably due to modifications with advanced glycation end products, were found in the amyloid deposits of dialysis related amyloidosis (DRA), and they were proposed as the amyloidogenic forms of beta 2m. The other modifications in beta 2m from amyloid deposits are partial proteolysis and single amino acid replacement (Asn by ASp at position 17). However, there are no data on the sequence of the different isoforms of beta 2 m from amyloid deposits. Amyloid deposits surgically obtained from the carpal tunnel from 13 dialysis treated patients and urine from 10 healthy volunteers and 5 living-related kidney donors were analyzed for beta 2m content. Two-dimensional gel electrophoresis (2D-PAGE) of beta 2m from amyloid deposits showed the presence of four or more isoforms with pIs < 5.7. All the spots migrating at 12 kDa Mr region and between 4 and 6 pH reacted with rabbit anti-human beta 2m antibody by Western blotting, confirming that they were beta 2m isoforms. beta 2m isoforms from the amyloid deposits were then separately purified with an IEF column (PB94, Pharmacia) for analysis. Enough quantities of three pure beta 2m isoforms could be obtained in two cases. The sequence analysis showed an intact N-terminus in all the isoforms. There was Asn in the 17th residue in all the isoforms sequenced. 2D-PAGE of urine from 8 out of the 10 healthy volunteers showed the presence of beta 2m. In two of them beta 2m also displayed four different isoforms. At least four isoforms were observed in urine of all the kidney donors. The present study shows that the elution peaks of three different beta 2m isoforms in gel isoelectrofocusing contain beta 2m with intact N-terminus. None of them have deamidated their 17th residue. More importantly, the beta 2m isoforms with lower pI are not specific for amyloidosis as they were found in urine from kidney donors and in normal volunteers. These results bring into question the hypothesis that dialysis related amyloidosis is due to the known modifications on beta 2m. They suggest that the precipitation of beta 2m into amyloid fibrils should result from the interaction of beta 2m with other factors with amyloid enhancing activity.

Regulation of human renal adenocarcinoma cell growth by retinoic acid and its interactions with epidermal growth factor

Retinoic acid (RA) is a natural derivative of vitamin A which regulates the growth and differentiation of epithelia. We have previously proposed that RA participates in compensatory kidney growth and reported that RA inhibits rat mesangial cell growth. This paper describes the effects of RA on a human renal adenocarcinoma cell line (PAD) under different growth conditions, and its interactions with epidermal growth factor (EGF). PAD cells were shown to express RA receptors alpha and beta by Northern blot analysis. In serum free cultures, addition of RA (10(-7) M) markedly increased thymidine incorporation by PAD cells (155 +/- 7% mean +/- SE vs. control in 6 separate experiments; P < 0.0001). RA also caused a significant increase in thymidine incorporation by PAD cells under conditions of rapid growth in serum supplemented medium (115 +/- 2% vs. control; P < 0.001). RA by itself was unable to reverse contact inhibition of PAD cell growth (NS vs. control), but it synergistically enhanced the mitogenic effect of EGF on confluent monolayers (110 +/- 0.6% vs. EGF alone; P < 0.05). Northern blot analysis demonstrated that PAD cells express EGF receptor mRNA, and this was not significantly modified by the addition of RA. Growth arrested (serum starved) PAD cells expressed RAR-alpha mRNA which was upregulated eightfold at three hours following the addition of 10% FCS. Thus, our data show that RA is directly mitogenic for serum starved human renal adenocarcinoma cells and that it exerts complex modulation of cell growth in the presence of EGF and serum components.

Single kidney function: early and late changes in urate transport after nephrectomy

Renal urate transport was studied by means of pyrazinamide (PZA) and probenecid (PB): (a) before and at 2, 6, 24 weeks (24 patients), (b) 1 to 30 years after uninephrectomy in 27 and 12 patients with Ccr greater than 80 and 30 to 70 ml/min, respectively. Uninephrectomy was followed by important tubular urate transport modifications during at least two weeks, which lead to a marked uricosuria as indicated by significant increase in FEur (mean value +/- SD, 0.228 +/- 0.059 vs. 0.097 +/- 0.014 and 0.099 +/- 0.019 in normals and chronically diseased solitary kidneys). Reduced response to PZA and PB suggests a diminished reabsorptive capacity for urate mainly at the presecretory site which persisted after FENa normalization. Tubular compensations were presumably complete at six weeks, since pattern of urate transport returned to normal with an almost complete reabsorption of filtered urate load (99%) and a percentage of postsecretory reabsorption (80%) very close to those seen in normal subjects with a pair of kidneys. The adjustment in urate excretion in solitary kidneys was achieved by a significant increase of secreted urate as compared with 50% of pre-uninephrectomy values. Thus, increased urate secretion by the remaining intact organ is sufficient to maintain urate balance with a normal serum level.

Molecular mechanisms of tubulointerstitial hypertrophy and hyperplasia

Adult kidneys, which are principally composed of tubulointerstitium, do not normally regenerate or expand their working pool of functional cells at a very high rate. Loss of kidney tissue, however, can lead to some compensatory renal enlargement. The catalytic forces initiating such exchanges have not been fully articulated by current experimental endeavors. Increasing evidence, nevertheless, does suggest that factors other than simple changes in renal hemodynamics may be involved in this process. Different cellular elements in the tubulointerstitial microenvironment probably modulate changes in tubular enlargement or size through a complex cytokine network. Autocrine and paracrine stimulation of enlargement by different local growth factors also seem to play a pivotal role. After binding to cellular receptors, these factors activate signal transduction pathways resulting in expression of immediate early genes, which by themselves can synchronize the expression of subsequent genes through the medium of transacting factors. The renal enlargement response can also be modified by endocrine hormones that can activate such genes directly and/or stimulate other adjunctive processes, like receptor expression for the regional binding of growth factors. Furthermore, renal enlargement is under negative feedback of inhibitory factors like TGF beta. It is possible, for example, that special genes exist which are only expressed to arrest enlargement. It has been further suggested that activation of the Na+/H+ antiporter is a common denominator in renal enlargement. Recent findings, however, indicate that the activation of this antiporter is not always necessary, and might rather be a parallel event rather than a key phenomena in tubular enlargement. G0/G1 transition of tubular cells seems to involve similar factors in tubular hypertrophy and hyperplasia. The factors which are responsible for the final determination of the enlargement pattern (hypertrophy vs. proliferation) are unknown. The separation between hypertrophy and hyperplasia, although suggested by striking differences in cellular regulation, may be somewhat artificial, since responses leading to tubular enlargement also exist in circumstances where hyperplasia and hypertrophy are combined events. Recently it has been proposed that growth factors stimulate gluconeogenesis in proximal tubular cells producing hyperplasia, whereas factors inhibiting gluconeogenesis might induce hypertrophy. Whether the common pathway message of this intriguing hypothesis is correct still requires further validation.(ABSTRACT TRUNCATED AT 400 WORDS)

Atrial natriuretic peptide and renal adaptation to contralateral nephrectomy in healthy man

Atrial natriuretic peptide (ANP), angiotensin II (AII), aldosterone (Aldo) and arginine vasopressin (AVP) in plasma were determined in 12 healthy renal transplant donors before and 5, 12, 26, 54 days after uninephrectomy (Nx) in order to study the possible role of these hormones in functional adaptation to acute reduction in renal mass. Glomerular and tubular function was studied by measurements of the clearances of 51Cr-EDTA, lithium, sodium, potassium, and albumin. ANP was 7.4 +/- 3.1 pmol l-1 (mean +/- SD) before Nx and 8.7 +/- 6.1 pmol l-1 at 5 days after Nx and remained at this level through the observation period. Aldo showed a non-significant transient fall at 5 days after Nx. AII and AVP remained normal after Nx. At 5 days after Nx glomerular filtration rate (GFR) of the remaining kidney had risen from 45 +/- 7 ml min-1 before Nx to 57 +/- 8 ml min-1 (p less than 0.01), lithium clearance had risen from 13 +/- 2 ml min-1 before Nx to 20 +/- 7 ml min-1 (p less than 0.01), and sodium and water balance was normal. To conclude, plasma ANP, AII, Aldo and AVP do not appear to be responsible for the hyperfiltration and depression of fractional proximal sodium and water reabsorption observed in recently uninephrectomized man with normal sodium and water balance.

Renal reserve filtration capacity before and after kidney donation

Renal reserve filtration capacity (RRFC) was investigated in 20 kidney donors before and within 3 months after uninephrectomy. Glomerular filtration rate (GFR) was measured by the clearance of 125I-iothalamate, and effective renal plasma flow (ERPF) was determined by the clearance of 131I-hippurate. RRFC was tested by infusion of a low dose of dopamine, by intravenous administration of an amino acid solution and, finally, by combined infusion of amino acids and low-dose dopamine. After kidney donation, the median value of the GFR was 65% of its initial value. The median value of the ERPF was 69% of its value before uninephrectomy. The filtration fraction declined significantly from 0.251 to 0.238 (medians; P less than 0.02). Median values for dopamine-induced increases in GFR were 13.8% before and 5.3% after kidney donation (P less than 0.005). Infusion of amino acids led to an increase in GFR of 11.2% before and 9.6% after donation (NS). During combined infusion, the median values for the increases in GFR were 20.0% before and 12.6% after uninephrectomy (P less than 0.02). Median changes in ERPF before and after kidney donation were 33.4 vs. 23.0% during dopamine infusion (P less than 0.005), 10.0 vs. 8.3% during amino acid infusion (NS), and 36.2 vs. 24.3% during the combined infusion of dopamine and amino acids (P less than 0.02). Infusion of dopamine induces a decrease in renal vascular resistance, resulting in a rise in glomerular blood flow. Since RRFC tested by means of dopamine infusion was significantly decreased after kidney donation, it is concluded that glomerular hyperfiltration after kidney donation is at least partially due to a rise in glomerular blood flow.

Retinoic acid affects the cell cycle and increases total protein content in epithelial cells

Retinoids and particularly retinoic acid (RA) have been incriminated in the adaptation to uninephrectomy and compensatory kidney growth in humans. However, there is no data assessing the effects of RA on renal cells. Since the bulk of the compensatory kidney growth is due to tubular cells, we studied the effects of RA, retinol and epidermal growth factor (EGF) on a rabbit kidney epithelial cell line RK13 in culture. RA significantly increased thymidine incorporation by 42 +/- 8% (P less than 0.01). This increase appeared as soon as three hours after adding RA and could still be observed after five days. Total protein content was also increased by RA by 37 +/- 4% (P less than 0.01). Flow cytometer analysis showed a significant decrease in the percentage of resting cells (G0-G1 phases) induced by RA (-9.4 +/- 2%; P less than 0.01). We observed similar results in growth factor free medium, and the RA induced changes were the same in confluent and non-confluent cells. Retinol did not modify thymidine incorporation or total protein content. EGF increased by 75% thymidine incorporation (P less than 0.01). In serum free conditions RA failed to have a synergistic effect with EGF. These data show that RA is able to induce modifications in kidney epithelial cells compatible with those observed in hypertrophy while retinol is not. These modifications are not due to other growth factor potentiation but to RA itself, and are independent of the contact-inhibition phenomenon.