[Micro RNA-155 expression in hemodialysis PBMC]

INTRODUCTION

MicroRNAs (miR) are fragments of non-coding RNA acting at post-transcriptional level, which modulate gene expression, and play a key role in several pathophysiological pathways. The aim of this study is to analyze the expression of miR-155 in basal Peripheral Blood Mononuclear Cells (PBMC) of chronic hemodialysis (HD) patients, before and after standard 4 -hour sessions, and after PHA stimulation compared with PBMC from healthy subjects.

METHODS

miR-155 was isolated from chronic HD patients' PBMC and from PBMC derived from healthy subjects. Expression levels were quantified with Real-Time PCR; PCR reactions were performed using a specific thermocycler and cycle threshold levels were calculated using dedicated software. Blood samples were taken from HD patients after the long inter-dialytic interval. Data were expressed as MSE and statistical differences were calculated with t-test.

RESULTS

Relative quantity (RQ) of pre-dialysis MiR-155 was 3.770.62 times higher than the control group (P=0,003). There was no significant difference before and after hemodialysis sessions. Pre-dialysis mir-155 RQ in PHA PBMC was 1.790.59 times higher than non stimulated PBMC (P=0.019).

CONCLUSIONS

these preliminary data show a significant miR-155 up-regulation of HD PBMC when compared to PBMC from healthy individuals. An additional up-regulation was observed in HD PHA PBMC. Similar miR-155 expression was found in HD PBMC comparing pre and post-hemodialysis sessions.

[Regulatory T cells in kidney transplant recipients]

Immunosuppressive drugs are essential for the prevention of acute transplant rejection but some may not promote long-term tolerance. Tolerance to self-antigens is ensured naturally by several mechanisms; one major mechanism depends on the activity of regulatory T lymphocytes (Treg), particularly CD4+CD25+ T cells. The transcription factor forkhead box protein 3 (Foxp3) has been identified as a molecular marker for Treg cells. The direct effects of immunosuppressive drugs on CD4+CD25+ cells are uncertain. In the clinical setting, basiliximab used in the induction phase of immunosuppression effectively reduced the number of acute rejection episodes. We studied the effects of the most widely used immunosuppressive induction regimens including cyclosporine, mycophenolate mofetil, steroids, and anti-CD25 monoclonal antibody (basiliximab) on the capacity to regulate human Treg in vivo. Twenty first cadaveric kidney transplant recipients (14 men, 6 women) were enrolled in the study. Blood samples were collected before kidney transplant and after one month. Blood sampling was done immediately before the administration of immunosuppressive therapy after an overnight fast. None of the transplant recipients presented laboratory or clinical signs of infection or acute rejection. The number and percentage of CD4+CD25+ and Foxp3+ T cells were determined by fluorescence activated cell sorter (FACS) analysis. Our results showed absence of both CD4+CD25+ and CD4+CD25+ Foxp3+ T cells one month after transplant. Peripheral CD4+CD25-Foxp3+ T cells significantly decreased after transplant but did not disappear. These preliminary data suggest that immunosuppressive induction therapy with basiliximab completely suppresses CD4+CD25+ regulatory cells and significantly reduces the total number of Foxp3+ lymphocytes.

The effect of sirolimus- or cyclosporine-based immunosuppression effects on T-cell subsets in vivo

While sirolimus (SRL) is thought to be a non-nephrotoxic agent, cyclosporine A (CsA) toxicity is a serious problem in kidney transplantation. We compared the effects of the two drugs on T-helper (Th) subsets in kidney transplant patients. We examined 24 first cadaver kidney recipients equally randomized to receive SRL/mycophenolate mofetil (MMF)/methylprednisolone (MP), or cyclosporine with either MMF or MP. The Th1 and Th2 subsets in peripheral blood were separated based on their production of interferon-gamma (INFgamma) or interleukin (IL)-4/IL-5. The lymphocytes were stimulated with phytohemoagglutinin or with allogenic CD3-depeted and irradiated antigen-presenting cells. Furthermore, the conversion potential of Th0 to Th1 was determined by measuring IL-12 and IL-18 levels after lipopolysaccharide challenge. When peripheral blood lymphocytes taken from SRL-treated patients were stimulated by phytohemoagglutinin, there were significantly lower INFgamma-producing cells compared with the lymphocytes taken from patients treated with CsA. The number of IL-4/IL-5-producing cells did not differ among the patient groups. Release of IL-12 but not IL-18 from peripheral lymphocytes following treatment with lipopolysaccharide was significantly lower in the SRL-treated patients. These results show that compared with CsA, SRL caused a significant decrease in the Th1 lymphocyte subset associated with a significant reduction of IL-12 release.

Influence of methylprednisolone on plasma homocysteine levels in cadaveric renal transplant recipients

The aim of the present study was to investigate plasma homocysteine levels in renal transplant recipients in the course of steroid-based or steroid-free immunosuppression. Data from 32 patients were retrospectively analyzed according to the steroid immunosuppressive regimen. The 20 recipients on methylprednisolone (MP) plus cyclosporine (CyA) or tacrolimus (TRL) (n = 20) showed similar creatinine levels when compared with those on calcineurin inhibitors plus mycophenolate mofetil (MMF; n = 12), (1.6 +/- 1.5 vs 1.6 +/- 0.4 mg/dL; P = NS) but significantly higher total plasma homocysteine (tHcy) levels (28.5 +/- 12.5 vs 16.3 +/- 5.5 micromol/L; P < .05). No differences of tHcy levels have been observed when patients were analyzed according to CyA- or TRL-based immunosuppression regardless of MP or MMF associations. Our data suggest that recipients, particularly those on steroid-based immunosuppression, should receive homocysteine-lowering treatment early after transplantation.

[Changes is Th1/Th2 balance in hemodialysis patients: effect of different membranes]

BACKGROUND

Hemodialysis (HD) patients present an immunodeficiency that is mainly related to the defect of cell-mediated immunity. We have previously shown the polarisation of T-helper cells toward the phenotype in HD treatment with cuprophan membrane. In the present study, we have examined the effect of a Vitamin E-coated dialyser (Excebrane, VE) on the activity of the two Th subsets.

METHODS

We studied 8 healthy controls and 10 patients on RDT for at least 6 months with cellulose membrane (AC), then switched to HD-VE. Blood was collected from HD patients while on treatment with AC, and after 1 year of treatment with VE. CD4+ cells were isolated from peripheral blood mononuclear cells (PBMC) by negative selection, treating PBMC with a cocktail of anti-CD8, -CD16, -CD19, -CD36 and -CD56 antibodies labelled with magnetic beads, and passing them through a magnetic field. The collected Th cells were cultured for 48 h with and without phytohemagglutinin (PHA). IFNgamma and IL-4 were measured in the supernatant using the ELISA assay.

RESULTS

The constitutive release of IL-4 by CD4+ cells was abated significantly by treatment with VE. IFNgamma released by mitogen-stimulated CD4+ recovered with VE.

CONCLUSIONS

This study demonstrates that treatment with vitamin E-coated dialyser improves the defect of PBMC function associated with cellulose membrane dialyser consisting of altered spontaneous and mitogen-stimulated cytokine release. The effects of vitamin E-coated filter, in particular the recovery of reactive IFNgamma production by Th1 cells and the restriction of spontaneous IL-4 release by Th2 cells may have clinical importance.

Polarization of T-helper lymphocytes toward the Th2 phenotype in uremic patients

T-helper (Th) lymphocytes consist of Th1 and Th2 subsets. Th1 cells are effectors of cell-mediated immunity and secrete interferon-gamma (IFN-gamma), which recruits new Th1 cells in cooperation with interleukin-12 (IL-12; produced by monocytes) and inhibits Th2 differentiation. Th2 cells produce IL-4 and IL-10, which inhibit IFN-gamma secretion and cell immunity. We investigated whether the impaired immune response in uremia is associated with an altered balance of Th1/Th2. Peripheral-blood mononuclear cells (PBMCs) were collected from patients with chronic renal failure (CRF) on conservative treatment (CRF patients), patients with end-stage renal disease (ESRD) on regular hemodialysis therapy (ESRD-HD patients), and healthy controls (CON). CD4(+) cells were isolated from PBMCs by negative selection using a magnetic labeling system. PBMCs and purified CD4(+) cells were cultured in Iscove's medium and Iscove's medium plus mitogens (phytohemagglutinin and lipopolysaccharide). IFN-gamma, IL-12, IL-4, and IL-10 were measured in supernatant. The constitutive release of IL-4 and IL-10 by PBMCs and CD4(+) cells of CRF and ESRD-HD patients was increased by five to eight times in comparison with CON (P < 0.001). Constitutive IFN-gamma release by PBMCs of ESRD-HD patients was undetectable, although they secreted an increased amount of IL-12. Mitogen-stimulated release of IFN-gamma by PBMCs and CD4(+) cells of CRF and ESRD-HD patients was blunted (average PBMCs: CON, 115.8 pg/2 x10(6) cells; CRF, 81.8 pg/2 x10(6) cells; ESRD-HD, 9.3 pg/2 x10(6) cells; CD4(+) cells: CON, 358.0 pg/5 x 10(5) cells; CRF, 165.4 pg/5 x 10(5) cells; ESRD-HD, 43.5 pg/5 x 10(5) cells). The ability of PBMCs of ESRD-HD patients to secrete IFN-gamma was recovered after IL-4 and IL-10 neutralization. Uremia is associated with a prevalence of Th1 over Th2 cells and a configuration of cytokine network that depresses cell-mediated immunity.

Hemodialysis prevents liver disease caused by hepatitis C virus: role of hepatocyte growth factor

Hemodialysis prevents liver disease caused by hepatitis C virus: Role of hepatocyte growth factor.

BACKGROUND

Hemodialysis increases markedly the serum levels of hepatocyte growth factor (HGF) so that regular dialysis treatment (RDT) mimics the regular administration of HGF as a drug. Therefore, we have studied the effects of dialysis-associated HGF production on the severity of liver damage caused by hepatitis C virus (HCV).

METHODS

Biochemical tests of liver function and liver biopsy were performed in 10 patients on RDT and in 11 patients without renal disease (WRD) converted to anti-HCV serum-positive test for the same time (48 +/- 4 months). The HGF serum concentration was measured by enzyme immunoassay. In patients on RDT, HGF was measured just before starting a dialysis session (T0), at 15 and 240 minutes of dialysis (T15 and T240), and 24 hours later (T24 hr).

RESULTS

Serum HGF was similar in WRD (average 0.17 ng/ml) as in RDT at T0 (0.25 ng/ml). In RDT serum HGF increased markedly at T15 and T240 (5.51 and 2.67 ng/ml, respectively, P < 0. 001 vs. WRD and T0) and was still higher than baseline at T24 hr (0. 41 ng/ml, P < 0.05). Both grade of necroinflammatory activity and stage of fibrosis were significantly lower in RDT than in WRD (both, P < 0.001). The number of apoptotic hepatocytes was also significantly reduced in patients on RDT compared with patients WRD.

CONCLUSION

These results show that HCV-related liver disease is more benign in patients on RDT. The phenomenon may depend on the marked and prolonged HGF release caused by dialysis.

Validation of the Ottawa ankle rules in children

OBJECTIVE

To assess whether the Ottawa ankle rules can be used to accurately predict which children with ankle and midfoot injuries need radiography.

METHODS

Prospective study with historical control group of all children aged 1-15 years presenting to Sheffield Children's Hospital accident and emergency department with blunt ankle and/or midfoot injuries during two five month periods before and after implementation of the Ottawa ankle rules.

RESULTS

In the study group 432 out of 761 (56.76%) patients received radiography compared with 500 out of 782 (63.93%) in the control group. This was a statistically significant reduction in radiography rate of 7.2% (95% confidence interval 2.3% to 12.1%, p <0.01). The sensitivity of the Ottawa ankle rules was 98.3% and the specificity 46.9%. There was no increase in the number of missed fractures (one in each group).

CONCLUSION

The Ottawa ankle rules can be applied in children to determine the need for radiography in ankle and midfoot injuries. Their implementation leads to a reduction in the radiography rate without leading to an increase in the number of missed fractures.

Diagnosis and management of transient ischaemic attacks in accident and emergency

Stroke is an important cause of morbidity and mortality. Often the first presentation of cerebrovascular disease is a TIA which will present to the A&E department. Patients who have had a TIA are at increased risk of stroke, myocardial infarction, and vascular death. The risk of stroke after a TIA is greatest in the first year (approximately 11.6%) with a risk of approximately 5.9% per year over the first five years. As the risk is highest in the first months following a TIA it is important that the patients are diagnosed accurately, investigated promptly, and referred appropriately for treatment in order that valuable time is not lost. For this reason A&E physicians have a valuable role in the initial assessment and management of the patient. It has been advocated that patients should be seen by a neurologist or physician with an interest in cerebrovascular disease within days of their symptoms and be prepared for surgery within two weeks after a TIA. While it is usually not possible to achieve this ideal, improved cooperation between A&E physicians and these neurologists, general physicians, and geriatricians should lead to the implementation of speedy efficient referral procedures which can only improve patient care. When you next see a patient with a TIA in the A&E department remember what they have to lose. Three questions relating to this article are: (1) How are TIAs subdivided and what clinical features allow this differentation? (2) What are the initial investigations that should be performed in A&E? (3) When are the risks of completed stroke greatest after a TIA? Enumerate these risks. How effective is aspirin at reducting this risks?

Stimulation of hepatocyte growth factor in human acute renal failure

Hepatocyte growth factor (HGF) is a potent mitogen for tubular cells. Experimental injury to the kidney is associated with HGF release both locally and by distant organs stimulated by circulating 'injurins'. In this study, the serum HGF concentration was measured in patients with acute renal failure (ARF). Normal subjects and chronic renal failure patients either not on dialysis or on regular dialysis treatment served as controls. Human mesangial cells were incubated with sera from ARF patients and controls. The serum HGF concentration was strikingly increased in ARF patients (478 +/- 68 ng/dl) and was normal in chronic renal failure patients not on dialysis (20 +/- 3 ng/dl) and in those on regular dialysis treatment (25 +/- 3 ng/dl). Serum of ARF patients strongly stimulated HGF release from mesangial cells (1,384 +/- 55 ng/ml) in comparison with normal serum (67 +/- 10 ng/ml). These results indicate that in ARF HGF participates in tubular repair both as an endocrine factor, released in the circulation, and as a paracrine substance, diffusing to the tubules from the mesangium.

Hemodialysis stimulates hepatocyte growth factor release

Studies were performed in 26 patients on regular dialysis treatment with cuprophane (CU), polymethylmetacrilate (PMMA) or cuprammonium (CAM) dialyzers. Controls were six patients with chronic renal failure but not on regular dialysis treatment (CRF) and six healthy subjects (N). Blood was collected at the start (T0), and at 15 (T15) and 240 (T240) minutes of dialysis to measure the serum hepatocyte growth factor (HGF) concentration and to study HGF production by peripheral blood mononuclear cells (PBMC) in vitro. The form of HGF (that is, inactive/monomeric, active/dimeric) present in the serum was analyzed by immunoblotting. In addition, the ability of serum to stimulate proliferation of tubular cells (HK-2) and HGF release by PBMC and fibroblasts (MRC-5) was investigated. At T0, serum HGF levels were identical to that of the controls. In patients treated with CU, serum HGF rose from 0.24 ng/ml at T0 to 7.44 ng/ml at T15, and remained high at T240. PBMC collected at T15 and T240 released significantly more HGF in vitro than those collected at T0. Serum at T15 stimulated proliferation of HK-2 cells and the release of HGF by PBMC and MRC-5 cells. The PMMA and CAM dialyzers had similar effects as the CU. These results indicate that dialysis induces a striking rise in serum HGF and a prompt circulation of factor(s) stimulating HGF release. Dialysis-activated PBMC release HGF.

Circulating serum lectins of patients with IgA nephropathy stimulate IL-6 release from mesangial cells

Previously, the authors reported that the serum of patients with immunoglobulin (Ig) A nephropathy stimulated peripheral leukocytes, and this effect was inhibited by nominal haptens for lectins. In vitro studies have shown that lectins can bind to rat mesangial cells and cause their activation. This study was performed to investigate whether the serum of IgA nephropathy patients contains lectins that activate mesangial cells, i.e., induce release of interleukin (IL)-6, a nephritogenic cytokine. The serum of patients was adsorbed by affinity chromatography on resins loaded with lectin-binding sugars. After adsorption, serum supernatant was collected and the resins were then eluted. Human mesangial cells were conditioned with native serum, post-adsorption supernatant, and eluate (all three at 10%) for 24 h, and the release of IL-6 was determined by ELISA. Normal serum was used as control. Incubation of mesangial cells with IgA nephropathy patients serum raised average IL-6 release from 8.5 pg/mL to 274.1 pg/mL. Adsorption in beta-D-glucose and N-acetyl-D-glucosamine caused a fall in the activity of patients' serum, to 17.0 and 63.7 pg/mL, respectively, and the activity lost was recovered in the eluate (185.2 and 142.7 pg/mL, respectively). Neither adsorption on N-acetyl-D-galactosamine nor on fucosylamine was associated with any effect on serum activity; accordingly, no activity was found in the eluates. Serum of patients with non-IgA mesangiocapillary nephritis did not stimulate mesangial cells. These results show that the serum of IgA nephropathy patients contains specific lectins that stimulate IL-6 nephropathy by mesangial cells and are, therefore, potential nephritogenic.

Inflammatory effects of peritoneal dialysis: evidence of systemic monocyte activation

We evaluated in peritonitis-free patients undergoing continuous ambulatory peritoneal dialysis (CAPD) the release of both interleukin-6 (IL-6) and beta-2-microglobulin (beta 2m) by cultured peripheral blood mononuclear cells (PBMC), as well as the levels of serum amyloid A (SAA), that is, the main hepatic acute phase protein during inflammation. The same measurements were obtained in hemodialysis (HD) patients, uremic non-dialyzed patients (ESRD) and healthy controls (CON). In CAPD, IL-6 production from PBMC was markedly increased in comparison to the control value (600.7 +/- 104.3 vs. 14.2 +/- 3.6 pg/3 x 10(6) PBMC/24 hr, P < 0.005). Similarly, a striking enhancement of the PBMC release of beta 2m was detected in CAPD with respect to CON (10.1 +/- 2.6 vs. 0.063 +/- 0.013 micrograms/3 x 10(6) PBMC/24 hr, P < 0.001). Also, the SAA levels were significantly greater in CAPD patients (21.3 +/- 8.7 micrograms/dl) than in controls (3.14 +/- 0.17 micrograms/dl, P < 0.05). Analogous increases of both IL-6 and beta 2m cell releases, as well as of SAA levels, were observed in HD patients. No difference concerning the three parameters was detected between CON and ESRD. In conclusion, CAPD induces per se PBMC activation with an enhanced release of both IL-6 and beta 2m; this is associated to higher levels of SAA. These systemic inflammatory effects are comparable to those observed in HD patients indicating that CAPD is similar to HD in terms of biocompatibility of the treatment.

Hemodialysis related interleukin-2 receptor release by peripheral blood mononuclear cells

To evaluate the effects of hemodialysis treatment on the spontaneous cell release of interleukin-2 receptor (IL-2R), we studied 19 hemodialyzed patients (HD), 9 non hemodialyzed patients with chronic uremia (UR, glomerular filtration rate: 8.4 +/- 1.8 ml/min), and 8 healthy control subjects (C). We measured the release of IL-2R in the supernatant of peripheral blood mononuclear cells (PBMC) cultured for 24 hrs in Iscove's medium as well as the plasma levels of IL-2R. A significant increase of IL-2R release was detected in the supernatant of PBMC harvested from HD patients (32.4 +/- 2.4 and 34.2 +/- 5.6 U/3 x 10(6) PBMC daily before and after HD, respectively) as compared with UR (16.6 +/- 5.2 U/3 x 10(6) PBMC daily) and C (21.4 +/- 3.8 U/3 x 10(6) PBMC daily). Similarly, IL-2R plasma levels were significantly higher in HD (378.5 +/- 164.6 U/ml) than in UR (189.5 +/- 89.3 U/ml) and C (11.2 +/- 2.68 U/ml). To summarize, the current study demonstrates: a) an enhancement of spontaneous IL-2R cell release in HD patients; b) an increase of sIL-2R plasma levels in UR patients possibly related to reduced metabolism and/or urinary excretion, because it was not associated with high IL-2R cell release; and c) a further increment of IL-2R systemic levels in HD likely secondary to the high cell release of IL-2R. Therefore, a chronic T cell activation with increased release of IL-2R secondary to the dialysis procedure is suggested.

Interleukin-2-induced renal dysfunction in cancer patients is reversed by low-dose dopamine infusion

Recombinant interleukin-2 (rIL-2) is widely used in patients with advanced cancer to enhance killer cell functions. However, the main drawback of rIL-2 therapy is the frequent development of oliguric acute renal failure (ARF), presumably due to a vascular leak syndrome. The aim of this study was to evaluate the effect of low-dose dopamine infusion on this form of ARF. Nine patients with metastatic renal cancer and previous unilateral nephrectomy were treated with a continuous intravenous infusion of rIL-2 (3 x 10(6) Cetus units/m2/d) for 5 days (study A). After 1 week, all the patients repeated the same cycle, but with the addition of a continuous intravenous infusion of dopamine (2 micrograms/min/kg body weight) that was started at the third day of treatment (study B). During study A, all patients showed a progressive (up to 34%) decrease of creatinine clearance. After rIL-2 withdrawal, these alterations persisted and were associated with a reduction in urinary output, sodium urinary excretion, and plasma protein. In study B, dopamine administration after renal function impairment (delta glomerular filtration rate = -44%) led to a prompt improvement of creatinine clearance. Creatinine clearance showed a further significant enhancement after the withdrawal of both drugs, reaching a value within the baseline range on the third day of follow-up. Similarly, the decline in urinary output and sodium excretion during rIL-2 was promptly counteracted by dopamine; in addition, after withdrawal of rIL-2 and dopamine, plasma protein levels were normalized. In conclusion, our data suggest that rIL-2-induced ARF in cancer patients is due to renal hypoperfusion mainly caused by a reduction in oncotic pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Low-dose dopamine induces early recovery of recombinant interleukin-2--impaired renal function

Recombinant interleukin-2 (rIL-2) can produce impairment of renal function with hypotension, fluid retention, elevated blood urea nitrogen, oliguria and low fractional sodium excretion; these side-effects are a common cause of reduction or interruption of rIL-2 infusion. The aim of this study was to investigate the control and treatment of renal toxicity induced by rIL-2 therapy. Here we show that dopamine, at a low dose of 2 micrograms/kg/min, completely prevented renal toxicity induced by rIL-2. While continuing rIL-2 therapy, 24-h continuous infusion of low-dose dopamine produced a rapid normalisation of urine output and a significant decrease in serum creatinine levels and body weight (P < 0.01), with an early and complete recovery of the rIL-2--impaired renal function: mean recovery time of renal function in patients treated with dopamine was significantly lower (P < 0.05) than in nontreated patients (4.8 days vs. 10 days, respectively).

Hemodialysis related induction of interleukin-6 production by peripheral blood mononuclear cells

Interleukin-6 (IL-6) has a complex spectrum of biological activities, for example, growth and differentiation of B cells and synthesis of acute-phase proteins by the liver. To evaluate the role of this cytokine in the inflammatory response induced by blood interaction with hemodialysis membranes, we have investigated the IL-6 synthesis and release in supernatant of 24-hour cultured peripheral blood mononuclear cells (PBMC) isolated from: (a) 10 hemodialyzed patients, (b) seven patients with advanced chronic renal failure (GFR less than or equal to 10 ml/min), and (c) eight healthy control subjects. In the same groups of subjects we evaluated the relationship between IL-6 synthesis and release and beta-2-microglobulin (beta 2m) production. Before and after dialytic treatment hemodialysis patient blood samples were drawn using the following criteria: (1) after two months of dialysis with cuprophan membranes, (2) after one and two months of dialysis with polymethylmethacrylate (PMMA) membranes, and finally, (3) after one further month of dialysis with cuprophan membranes. IL-6 was determined after 72 hours of incubation of PBMC supernatant serial dilutions with IL-6-dependent hybridoma cell line, 7TD1. Compared to IL-6 synthesis in control subjects (6.0 +/- 5.6 U/3 x 10(6) PBMC/24 hr), hemodialyzed patients, when treated with cuprophan membranes, showed significantly higher value of IL-6 production both before (23 +/- 13 U/3 x 10(6) PBMC/24 hr) and after (26.2 +/- 11.3 U/3 x 10(6) PBMC/24 hr) the dialytic session.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal functional reserve: its significance in normal and salt depletion conditions

The aim of this study was the evaluation, in healthy subjects, of the renal functional reserve (RFR), that is, the GFR increase induced by a combined infusion of amino acids (AA) and dopamine (D), in conditions of extracellular volume depletion caused by diuretic administration. In particular, this study was undertaken: a) to evaluate whether and to which extent, AA + D can reverse the functional GFR impairment induced by salt depletion, without volume restoration; b) to study whether any relationship may be found between the GFR in normal condition (the so-called "resting" GFR), and/or the renal functional reserve and the GFR impairment induced by salt depletion, in order to understand the role of both "resting" GFR and RFR in the degree of renal dysfunction induced by salt depletion. In control conditions the i.v. infusion of AA + D significantly increased RPF (+ 41% vs. baseline period) with a mean absolute increase of 211 ml/min. A similar pattern was observed in GFR behavior (+31.5% with 34 ml/min of mean absolute increase). A significant inverse exponential relationship was observed between GFR before AA + D i.v. infusion ("resting" GFR) and renal functional reserve (P less than 0.05), suggesting that, in normal conditions, these inversely related parameters may widely vary according to the tone of the glomerular arterioles. Following salt depletion, we observed a variable degree of GFR impairment. Both GFR and RPF were significantly decreased (-25.9%, P less than 0.05 and -29%, P less than 0.05, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Acute effects of ciclosporin on renal hemodynamics and urinary protein excretion in patients with the nephrotic syndrome

The possibility that the renal hemodynamic abnormalities associated with ciclosporin (CS) administration are enhanced in nephrotic patients (NP), leading to severe impairment of renal function and/or to modifications in proteinuria, has not hitherto been tested. Ten NP and 8 healthy subjects (NC) were examined before and after oral CS administration (10 mg/kg body weight in NP and 12 mg/kg body weight in NC: a lower dosage was adopted in NP because of edema overestimating the actual body weight) under water diuresis by standard renal clearance methods. Basal blood volume was lower in NP. Blood CS levels were not significantly different in the two groups. Basal glomerular filtration rate (GFR) was similar in NP and NC, while renal plasma flow (RPF) was lower in NP. After CS, both GFR and RPF significantly decreased in the two groups, but the percent decrease in inulin clearance was greater in NP. Filtration fraction increased only in NC. Basal renal vascular resistances were greater in NP, and significantly increased after CS in both groups. Basal fractional sodium excretion (FENa) was lower in NP: after CS FENa decreased only in NC. Neither plasma renin activity, nor plasma aldosterone changed after CS. When urinary protein excretion (UP) was corrected by GFR, no change was observed after CS; by contrast, selectivity of proteinuria (as assessed by the CIgG/CTransferrin ratio) markedly increased. Our data indicate that CS induces a greater fall in the GFR in hypovolemic NP than in healthy subjects, probably because in the former GFR becomes extremely plasma flow dependent.(ABSTRACT TRUNCATED AT 250 WORDS)

Bicarbonate and calcium kinetics in postdilutional hemodiafiltration

Hemodiafiltration (HDF) is a very effective blood treatment resulting from the coupling of dialysis and hemofiltration and leading to reduction of dialysis time. The aim of this study was to evaluate the balance of bicarbonate and calcium through the filter during postdilutional HDF (with an ultrafiltration flow rate of 70 ml/min) and to verify the effect of ultrafiltration on the kinetics of these two solutes. The study was performed by simultaneously collecting three blood samples (at filter inlet and outlet and after reinfusion) at different ultrafiltration flow rates (12.5-90 ml/min), to measure blood pH, pCO2, plasma total CO2(TCO2), total calcium, ionized calcium and plasma protein concentration. Plasma bicarbonate concentration was calculated by measuring plasma TCO2. The results showed an inverse linear relationship between bicarbonate (r: -0.7938; p less than 0.001) and calcium (r: -0.8731; p less than 0.001) balance and ultrafiltration flow rate. In particular, in postdilutional HDF both bicarbonate and calcium balances through the filter were negative at ultrafiltration flow rates greater than 40 and 55 ml/min, respectively. The negative bicarbonate balance, however, was corrected by reinfusing a substituting solution containing bicarbonate (40 mmol/l). By contrast, the negative calcium balance cannot be corrected by reinfusion and requires a greater calcium concentration in the dialysate and oral calcium supplements.

Effects of a two-month treatment with low oral doses of cyclosporin on renal function

To test the effects of short-term therapy with low doses (LD) of cyclosporin A (CsA) in subjects with normal renal function, seven patients receiving CsA to treat psoriasis were studied. Clearances in maximal H2O diuresis were performed to evaluate changes in GFR (CIn), RPF (CPAH) and tubular function before starting CsA (BAS), after 2 days (S1) and 1 month (S2) of oral therapy with 5 mg/kg per day CsA. The study was repeated at the withdrawal of CsA after tapering (S3) and 2 months after the withdrawal (S4). The studies were performed 12 h after the evening dose of CsA. RPF was significantly less than in BAS throughout the therapy and returned almost to basal values in S4. GFR was significantly less than in BAS both in S2 and in S3. In S4, in spite of an increase, GFR was still significantly less than in BAS. Both in S2 and in S3 proximal tubular fractional sodium reabsorption was significantly less than in BAS and, consequently, both sodium delivery to diluting segments and sodium reabsorption in diluting segments increased. Moreover, both in S2 and in S3 fractional sodium reabsorption in diluting segments and free-water generation were greater than in BAS. In S4 tubular function returned almost to basal values. Our data suggest that short-term therapy with low dose CsA impairs renal function; this impairment is not completely reversed after drug withdrawal.