Treatment-limiting renal tubulopathy in patients treated with tenofovir disoproxil fumarate.

OBJECTIVES: Tenofovir disoproxil fumarate (TDF) is widely used in the treatment or prevention of HIV and hepatitis B infection. TDF may cause renal tubulopathy in a small proportion of recipients. We aimed to study the risk factors for developing severe renal tubulopathy. METHODS: We conducted an observational cohort study with retrospective identification of cases of treatment-limiting tubulopathy during TDF exposure. We used multivariate Poisson regression analysis to identify risk factors for tubulopathy, and mixed effects models to analyse adjusted estimated glomerular filtration rate (eGFR) slopes. RESULTS: Between October 2002 and June 2013, 60 (0.4%) of 15,983 patients who had received TDF developed tubulopathy after a median exposure of 44.1 (IQR 20.4, 64.4) months. Tubulopathy cases were predominantly male (92%), of white ethnicity (93%), and exposed to antiretroviral regimens that contained boosted protease inhibitors (PI, 90%). In multivariate analysis, age, ethnicity, CD4 cell count and use of didanosine or PI were significantly associated with tubulopathy. Tubulopathy cases experienced significantly greater eGFR decline while receiving TDF than the comparator group (-6.60 [-7.70, -5.50] vs. -0.34 [-0.43, -0.26] mL/min/1.73 m2/year, p < 0.0001). CONCLUSIONS: Older age, white ethnicity, immunodeficiency and co-administration of ddI and PI were risk factors for tubulopathy in patients who received TDF-containing antiretroviral therapy. The presence of rapid eGFR decline identified TDF recipients at increased risk of tubulopathy.

The role of tenofovir alafenamide in future HIV management.

HIV infection has become a chronic condition rather than an acute life-threatening disease in developed countries, thanks to consistent innovation and evolution of effective interventions. This has altered HIV management and created new challenges. People living with HIV (PLWHIV) are living longer and so encounter comorbidities linked not only with their disease, but also with ageing, lifestyle and chronic exposure to antiretroviral therapy (ART). Although longevity, viral suppression and the prevention of viral transmission remain key goals, more needs to be achieved to encompass the vision of attaining an optimum level of overall health. Treatment choices and management practices should ensure patients' long-term health with minimal comorbidity. Treatments that balance optimal efficacy with the potential for improved long-term safety are needed for all patients. In this review, we consider the evolution and development of tenofovir alafenamide (TAF), a novel prodrug of tenofovir which offers high antiviral efficacy at doses over ten times lower than that of tenofovir disoproxil fumarate (TDF). Emerging clinical data suggest that elvitegravir, cobicistat, emtricitabine and TAF (E/C/F/TAF) as a single-tablet regimen offers highly effective viral suppression in treatment-naïve and treatment-experienced patients with an improved renal and bone safety profile compared with TDF, this having been demonstrated in diverse groups including patients with existing renal impairment and adolescents. The profile of TAF identifies it as an agent with a promising role within future ART regimens that aim to deliver the vision of undetectable viral load, while requiring less monitoring and having a safety profile designed to minimize comorbid risks while supporting good long-term health.

An in vitro model for the pro-fibrotic effects of retinoids: mechanisms of action.

BACKGROUND AND PURPOSE: Retinoids, including all-trans retinoic acid (tRA), have dose-dependent pro-fibrotic effects in experimental kidney diseases. To understand and eventually prevent such adverse effects, it is important to establish relevant in vitro models and unravel their mechanisms. EXPERIMENTAL APPROACH: Fibrogenic effects of retinoids were assessed in NRK-49F renal fibroblasts using picro-Sirius red staining for collagens and quantified by spectrophotometric analysis of the eluted stain. Other methods included RT-qPCR, immunoassays and matrix metalloproteinase (MMP) activity assays. KEY RESULTS: With or without TGF-ß1, tRA was dose-dependently pro-fibrotic, notably increasing collagen accumulation. tRA and TGF-ß1 additively suppressed expression of mRNA for MMP2, 3 and 13 and suppressed MMP activity. tRA, in the presence of TGF-ß1, induced plasminogen activator inhibitor-1 (PAI-1) mRNA and they additively induced PAI-1 protein expression. A PAI-1 inhibitor, a pan-retinoic acid receptor (RAR) antagonist and a pan-retinoid X receptor (RXR) antagonist each partially prevented the pro-fibrotic effect of tRA. The dose-dependent pro-fibrotic effects of a pan-RXR agonist were similar to those of tRA. A pan-RAR agonist showed weaker, less dose-dependent pro-fibrotic effects and the pro-fibrotic effects of RARα and RARß-selective agonists were even smaller. An RARγ-selective agonist did not affect fibrogenesis. CONCLUSIONS AND IMPLICATIONS: An in vitro model for the pro-fibrotic effects of retinoids was established in NRK-49F cells. It was associated with reduced MMP activity and increased PAI-1 expression, and was probably mediated by RXR and RAR. To avoid or antagonize the pro-fibrotic activity of tRA, further studies on RAR isotype-selective agonists and PAI-1 inhibitors might be of value.

Spectrum of chronic kidney disease in HIV-infected patients.

OBJECTIVES: The aim of the study was to investigate the prevalence and aetiology of chronic kidney disease (CKD) and trends in estimated glomerular filtration rate (eGFR) in HIV-infected patients. METHODS: Ascertainment and review of CKD cases among patients attending King's College and Brighton Hospitals, UK were carried out. CKD was defined as eGFR <60 mL/min for > or =3 months. Longitudinal eGFR slopes were produced to examine trends in renal function before, during and after exposure to indinavir (IDV) or tenofovir (TFV). RESULTS: CKD prevalence was 2.4%. While HIV-associated nephropathy accounted for 62% of CKD in black patients, 95% of CKD in white/other patients was associated with diabetes mellitus, hypertension, atherosclerosis and/or drug toxicity. Exposure to IDV or TFV was associated with an accelerated decline in renal function (4.6-fold and 3.7-fold, respectively) in patients with CKD. In patients initiating IDV, age > or =50 years increased the odds of CKD [odds ratio (OR) 4.9], while in patients initiating TFV, age > or =50 years (OR 5.4) and eGFR 60-75 mL/min (OR 17.2) were associated with developing CKD. CONCLUSION: This study highlights the importance of metabolic and vascular disease to the burden of CKD in an ageing HIV-infected cohort. In patients who developed CKD, treatment with IDV or TFV was associated with an accelerated decline in renal function.

The role of geranylgeranylated proteins in human mesangial cell proliferation.

The Rho family of guanine 5'-triphosphatases (GTPases) play a key role in regulating cell proliferation, tubulointerstitial fibrosis, and glomerular hemodynamics. The post-translational prenylation of RhoGTPases by the addition of a geranylgeranyl moiety is critical for cellular localization and signaling activity. This study investigates the effects of (i) inhibiting geranylgeranylation (GG) in human mesangial cell (HMC) proliferation and apoptosis, using GGTI 298, a specific inhibitor of GG and (ii) lovastatin, an HMG-coacetyl A-reductase inhibitor, which depletes the availability of prenylation substrates. HMC proliferation was assessed using an assay of viable cell number and measuring bromodeoxyuridine (BrdU) incorporation. Hoechst 33342 staining was used to determine apoptosis. Extracellular signal-regulated protein kinase (Erk)1/2 and Akt activation were analysed by Western blotting. Rho activation was determined using the Rhotekin pull-down assay. Immunocytochemistry was performed to study the effects on the actin cytoskeleton and RhoA localization. GGTI 298 (10-20 muM) and lovastatin (5-10 muM) potently inhibited platelet-derived growth factor and serum-stimulated HMC proliferation and induced apoptosis. These effects of lovastatin were attenuated by co-incubation with geranylgeranylpyrophosphate. C3 exoenzyme, a clostridial toxin that specifically targets Rho also inhibited BrdU incorporation and promoted apoptosis. GGTI 298 increased cytosolic expression of RhoA, prevented RhoA activation, and inhibited the activation of Erk1/2 and the survival protein Akt. GGTI 298, lovastatin, and C3 exoenzyme inhibit HMC proliferation and promote apoptosis. Inhibiting GG increases cytosolic RhoA expression, disrupts the actin cytoskeleton, and inhibits RhoA activation. These results suggest that targeting geranylgeranylated proteins with statins or GGTI 298 is a promising therapeutic strategy in human mesangioproliferative renal disease.

Distinct functions for Ras GTPases in the control of proliferation and apoptosis in mouse and human mesangial cells.

In previous work, we have demonstrated that Ras GTPases regulate proliferation in a range of human renal cells. The present work compares human and mouse mesangial cell (HMC and MMC) responses to specific knockdown of Ras genes with antisense oligonucleotides (AS-oligos), and examines the role of the p21 (cip1) and p27 (kip1) cyclin-dependent kinase inhibitors in these responses in mouse cells. HMC and MMC were lipofectin transfected with ras-targeted AS-oligo at 200-400 nM for 18 h followed by growth of cells in 20% serum for 18-72 h. Cell proliferation was assessed with an MTS assay and bromodeoxyuridine (BrdU) uptake. Apoptosis was quantified using nuclear stain with Hoechst 33342 dye. In MMC, Ha-ras AS-oligo caused an increase in apoptosis from <2% to 10-15% of cells after 18 h in serum (P<0.01). Control, Ki-ras and N-ras AS-oligos had minimal effects on apoptosis. BrdU uptake studies showed that BrdU+ve MMC were increased by 20-40% (P<0.05) after Ha-ras AS-oligo at 24 h; other ras AS-oligos were inactive. HMC number was reduced by 40-80% (P<0.01) at 48-72 h by both Ha-ras and Ki-ras AS-oligos. These actions were associated with reductions in BrdU+ve cells. In HMC, the ras AS-oligos did not induce apoptosis. p21(-,-) MMC showed exaggerated apoptotic responses to Ha-Ras AS-oligo. In mouse cells, Ha-Ras expression appears necessary to prevent apoptotic cell death; Ras expression does not appear necessary for cells to progress through the cell cycle. In human cells, Ras does not appear necessary to prevent apoptosis but Ha-Ras and Ki-Ras appear to be required for cell cycle progression.

Effects of endothelin-1 on K(+) currents from rat ventricular myocytes.

It has been suggested that the positive inotropic effect of the vasoactive peptide hormone, endothelin-1 (ET-1), involves inhibition of cardiac K(+) currents. In order to identify the K(+) currents modulated by ET-1, the outward K(+) currents of isolated rat ventricular myocytes were investigated using whole-cell patch-clamp recording techniques. Outward currents were elicited by depolarisation to +40 mV for 200 ms from the holding potential of -60 mV. Currents activated rapidly, reaching a peak (I(pk)) of 1310 +/- 115 pA and subsequently inactivating to an outward current level of 1063 +/- 122 pA at the end of the voltage-pulse (I(late)) (n = 11). ET-1 (20 nM) reduced I(pk) by 247.6 +/- 60.7 pA (n = 11, P < 0.01) and reduced I(late) by 323.2 +/- 43.9 pA (P < 0.001). The effects of ET-1 were abolished in the presence of the nonselective ET receptor antagonist, PD 142893 (10 microM, n = 5). Outward currents were considerably reduced and the effects of ET-1 were not observed when K(+) was replaced with Cs(+) in the experimental solutions; this indicates that ET-1 modulated K(+)-selective currents. A double-pulse protocol was used to investigate the inactivation of the currents. The voltage-dependent inactivation of the currents from potentials positive to -80 mV was fitted by a Boltzmann equation revealing the existence of an inactivating transient outward component (I(to)) and a noninactivating steady-state component (I(ss)). ET-1 markedly inhibited I(ss) by 43.0 +/- 3.8% (P < 0.001, n = 7) and shifted the voltage-dependent inactivation of I(to) by +3.3 +/- 1.2 mV (P < 0.05). Although ET-1 had little effect on the onset of inactivation of the currents elicited from a conditioning potential of -70 mV, the time-independent noninactivating component of the currents was markedly inhibited. In conclusion, the predominant effect of ET-1 was to inhibit a noninactivating steady-state background K(+) current (I(ss)). These results are consistent with the hypothesis that I(ss) inhibition contributes to the inotropic effects of ET-1.

Heterogeneous calcium responses to extracellular ATP in cultured rat renal tubule cells.

There is increasing evidence that extracellular ATP acting on purinoceptors may play an important signalling role in renal epithelial cells, often through alterations in cellular Ca(2+). In this paper effects of extracellular ATP and related purinoceptor agonists and antagonists on [Ca(2+)](i) have been studied in single cells from primary cultures of rat proximal tubule cells. Responses to 1--100 micromol/l ATP were heterogeneous; 55% of cells showed a transient rise in [Ca(2+)](i), 20% of cells showed a transient fall; in 25% there was no response. ATP actions on [Ca(2+)](i) were abolished by pre-treatment with thapsigargin. The P(2) receptor antagonist suramin unexpectedly increased the [Ca(2+)](i) response to ATP; the related antagonist XAMR 0721 did not significantly alter ATP responses. This difference is likely to arise from the inhibition of ATP hydrolysis by suramin. UTP, ADP and the non-hydrolyzable ATP analogue adenosine-5'-O-(3-thio)-triphosphate (ATP gamma S)produced similar increases in [Ca(2+)](i). The magnitude of the [Ca(2+)](i) responses to 100 micromol/l agonist gave an agonist potency order of ATP> or =ADP> or =UTP approximately ATP gamma S. Desensitisation experiments demonstrated the presence of more than one P2Y ATP receptor subtype on a single cell. These results are consistent with the expression of purinoceptors of both P2Y(1) and P2Y(2) subclasses on individual rat proximal tubule cells coupled to inositol trisphosphate-mediated release of intracellular calcium stores.

L-type calcium current of isolated rat cardiac myocytes in experimental uraemia.

BACKGROUND: End-stage renal failure is associated with a low-output cardiomyopathy, left ventricular hypertrophy and increased QTc dispersion. Cardiac dysfunction is prevalent in patients at the beginning of dialysis and is an important predictor of mortality. Ca(2+) influx through voltage-gated L-type Ca(2+) channels plays a key role in the excitation-contraction coupling of cardiac myocytes. The purpose of this study was to examine the effect of subtotal nephrectomy (SNx) in the rat on both cardiac L-type Ca(2+) currents and action potential duration. METHODS: Wistar rats underwent two-stage SNx; control rats (C) underwent bilateral renal decapsulation. Animals were sacrificed after 8 weeks, and ventricular myocytes were isolated. SNx rats showed a 2-fold increase in plasma urea and creatinine compared with C rats. Whole-cell patch clamp techniques were used to examine L-type Ca(2+) channel currents in isolated cardiac myocytes at 37 degrees C. In separate experiments, the epicardial monophasic action potentials of isolated perfused whole hearts from C and SNx rats were recorded. RESULTS: The amplitude and current-voltage relationships of the L-type Ca(2+) current were not significantly different in myocytes from C (n=11) and SNx (n=8) rats. However, the rate of inactivation of the Ca(2+) current was increased by approximately 15-25% (P<0. 05) in myocytes from SNx rats. The action potential duration (APD(33)) at the apex of the left ventricle was approximately 20% shorter (P<0.01) in hearts from SNx rats as compared with controls. CONCLUSIONS: Renal failure is associated with rapid inactivation of cardiac ventricular myocyte L-type Ca(2+) currents, which may reduce Ca(2+) influx and contribute to shortening of the action potential duration.

Alterations in outward K(+) currents on removal of external Ca(2+) in human atrial myocytes.

External divalent cations are known to play an important role in the function of voltage-gated ion channels. The purpose of this study was to examine the sensitivity of the voltage-gated K(+) currents of human atrial myocytes to external Ca(2+) ions. Myocytes were isolated by collagenase digestion of atrial appendages taken from patients undergoing coronary artery-bypass surgery. Currents were recorded from single isolated myocytes at 37 degrees C using the whole-cell patch-clamp technique. With 0.5 mM external Ca(2+), voltage pulses positive to -20 mV (holding potential = -60 mV) activated outward currents which very rapidly reached a peak (I(peak)) and subsequently inactivated (tau = 7.5 +/- 0.7 msec at +60 mV) to a sustained level, demonstrating the contribution of both rapidly inactivating transient (I(to1)) and non-inactivating sustained (I(so)) outward currents. The I(to1) component of I(peak), but not I(so), showed voltage-dependent inactivation using 100 msec prepulses (V(1/2) = -35.2 +/- 0.5 mV). The K(+) channel blocker, 4-aminopyridine (4-AP, 2 mM), inhibited I(to1) by approximately 76% and reduced I(so) by approximately 33%. Removal of external Ca(2+) had several effects: (i) I(peak) was reduced in a manner consistent with an approximately 13 mV shift to negative voltages in the voltage-dependent inactivation of I(to1). (ii) I(so) was increased over the entire voltage range and this was associated with an increase in a non-inactivating 4-AP-sensitive current. (iii) In 79% cells (11/14), a slowly inactivating component was revealed such that the time-dependent inactivation was described by a double exponential time course (tau(1) = 7.0 +/- 0.7, tau(2) = 90 +/- 21 msec at +60 mV) with no effect on the fast time constant. Removal of external Ca(2+) was associated with an additional component to the voltage-dependent inactivation of I(peak) and I(so) (V(1/2) = -20.5 +/- 1.5 mV). The slowly inactivating component was seen only in the absence of external Ca(2+) ions and was insensitive to 4-AP (2 mM). Experiments with Cs(+)-rich pipette solutions suggested that the Ca(2+)-sensitive currents were carried predominantly by K(+) ions. External Ca(2+) ions are important to voltage-gated K(+) channel function in human atrial myocytes and removal of external Ca(2+) ions affects I(to1) and 4-AP-sensitive I(so) in distinct ways.

Prenylation inhibitors in renal disease.

Members of the superfamily of Ras GTPase signalling proteins (monomeric G proteins) require post-translational carboxy-terminal prenylation to function. Prenylation is the covalent attachment of a hydrophobic prenyl group (either farnesyl or geranylgeranyl), which localises the GTPase to cell membranes. Ras proteins exert substantial control on cell proliferation and gene-transcription events, and prenylation inhibitors are now included in clinical trials for cancer. Many renal diseases are highly proliferative and are driven by a range of profibrotic cytokines. We hypothesise that inhibition of prenylation could be of substantial therapeutic benefit in such diseases, providing greater selectivity against abnormal cytokine-driven proliferation and fibrogenesis than current treatments available to nephrologists.

Evidence of a role for Ki-Ras in the stimulated proliferation of renal fibroblasts.

Progressive renal fibrosis is driven by a range of cytokines that act via membrane receptors and intracellular signaling cascades to evoke gene transcription events and related responses. The Ras family of GTPases has been implicated in many of these signaling cascades in model systems such as 3T3 fibroblasts. However, the roleof the specific Ras isoforms Ki, Ha, and N in the stimulation of renal fibroblasts has not been defined. In this study, Ras has been inhibited in primate renal fibroblasts (vero cells) using specific phosphorothioate oligodeoxynucleotides (oligos) targeting the three isoforms. Lipofectin transfection with 200 to 400 nM Ki-Ras oligo inhibited the epidermal growth factor- and fibroblast growth factor-stimulated proliferation of vero cells by 25 to 35% with a lesser effect on serum-stimulated growth. Oligos against Ha-Ras and N-Ras were inactive with respect to control oligo. Total cellular Ras protein (estimated by Western blotting) was reduced by 60 to 90% 24 h after transfection with Ki-Ras oligo. N-Ras, Ha-Ras, and control oligos were inactive. Total Ras synthesis over 4 h measured using [35S]-cys/met pulse chase was reduced by approximately 70% by Ki-Ras oligo and not altered by other oligos. The fractional prenylation of Ras was quantified from the discrete bands on polyacrylamide gel electrophoresis and was increased by the Ki-Ras oligo alone. These data demonstrate that these renal fibroblasts predominantly express the Ki isoform of Ras and that this GTPase plays a role in the stimulated proliferation of these cells. Ras GTPases may be a target for the inhibition of processes leading to renal fibrosis.

A randomized multicenter trial of the anti-ICAM-1 monoclonal antibody (enlimomab) for the prevention of acute rejection and delayed onset of graft function in cadaveric renal transplantation: a report of the European Anti-ICAM-1 Renal Transplant Study Group.

BACKGROUND: T-cell activation through T-cell receptor engagement requires co-stimulatory molecules and also adhesion molecules such as ICAM-1. Moreover ICAM-1 mediates leukocyte invasion from the blood into tissue during inflammatory processes. In animal studies using mouse monoclonal antibodies against ICAM-1 (enlimomab), renal allograft survival has been improved and reperfusion damage from ischemia reduced. The European Anti-ICAM-1 Renal Transplant Study (EARTS) was a randomized, double-blind, parallel-group, placebo-controlled study lastingl year and performed in 10 transplant centers in Europe. METHODS: A total of 262 recipients of cadaveric kidneys were given either enlimomab or a placebo for 6 days and were given triple immunosuppressive therapy of cyclosporine, azathioprine, and prednisolone. The primary efficacy endpoint was the incidence of the first acute rejection within 3 months, and each event was assessed by a committee including investigators and independent pathologists. RESULTS: There was no significant difference in the incidences of first acute rejection at 3 months between the placebo and enlimomab groups (39% vs. 45%), and enlimomab did not reduce the risk of delayed onset of graft function (DGF) (26% vs. 31%). Neither was there a difference in patient survival (95% vs. 91%) or graft survival (89% vs. 84%) at 1 year. Fatal events occurred in 19 (7%) patients (7 placebo, 12 enlimomab). Clinically, the most important non-fatal adverse events were infections; however, there was no statistically significant difference between the incidences in the two groups (70% vs. 79%). CONCLUSION: Short term enlimomab induction therapy after renal transplantation did not reduce the rate of acute rejection or DGF.

Alkalinization and hemodialysis in severe salicylate poisoning: comparison of elimination techniques in the same patient.

We report the case of a man who took two overdoses of aspirin, on each occasion suffering a grand mal fit with blood levels of salicylate of over 5 mmol/l. The first event was treated with hemodialysis but without effective alkalinization, and the second with alkalinization but without hemodialysis. The rate of decline in salicylate concentration was faster with alkalinization in the first 4 hours. Similar salicylate levels were achieved with both techniques by 24 hours post-overdose. If a case of salicylate poisoning is to be treated with hemodialysis, treatment with alkalinization should still be given without delay, in order to prevent acidemia and to promote elimination of as much salicylate as possible via the kidneys.

CMV infection is associated with transplant renal artery stenosis.

Transplant renal artery stenosis (TRAS) is a significant cause of graft dysfunction, with no clearly defined aetiology. Evidence suggests a role for cytomegalovirus (CMV) infection in cardiac transplant vasculopathy and in native coronary artery restenosis after angioplasty. We investigated the relationship between CMV infection after renal transplantation and subsequent development of TRAS. Of 917 patients receiving renal transplants at a single centre from 1978 to 1994, 75 had TRAS diagnosed by angiography. Each was paired with a control transplanted patient with no TRAS, matched for age, sex, year of transplant and number of grafts. Incidence of CMV infection between transplantation and the time of diagnosis of TRAS was assessed in both groups, using clinical and serological criteria to assign patients to three groups: definite CMV infection (CMV-DEF), possible infection (CMV-POSS) and no evidence of infection (CMV-NUL). CMV-DEF was significantly more common in TRAS than in controls (36 vs. 12, respectively, p < 0.001) and CMV-NUL was less common (TRAS 15, controls 33). We have previously reported an increased incidence of acute rejection in patients with TRAS. The subset of patients with no rejection episodes also had significantly more CMV-DEF cases in the TRAS group (54%) than in controls (10%) (p = 0.002). The data are consistent with the hypothesis that CMV infection can contribute to the development of TRAS. The relationship between CMV and TRAS did not arise from an excess of anti-rejection treatment in the TRAS group. CMV-induced large-vessel damage in immunosuppressed patients may occur through local infection and the mitogenic actions of viral gene products within cells of the vessel wall.

Characterization of human erythrocyte choline transport in chronic renal failure.

BACKGROUND: Membrane transport of choline cations is elevated in renal failure in erythrocytes and cerebral tissue but the origins and clinical importance of this are unknown. METHODS: The membrane transport changes have been characterized using erythrocytes from patients on maintenance haemodialysis (HD), patients on continuous ambulatory peritoneal dialysis (CAPD), and control subjects. Data were obtained from cells depleted of intracellular choline to create zero-trans (ZT) conditions for choline influx. [14C]-choline influx measurements provided a kinetic description of choline flux as the sum of a saturable transport system (defined by Vmax and Km) and an apparent diffusion pathway. Inhibition of choline transport by hemicholinium-3 (HC-3), quinine and N-ethylmaleimide (NEM) has been studied. Actions of three cationic polyamine putative uraemic toxins (putrescine, spermidine, spermine) were tested in control erythrocytes. RESULTS: Mean (SEM) Vmax (ZT) was increased in HD at 45.0 (3.0) mumol/l cells/h and in CAPD at 46.6 (2.5) mumol/l cells/h compared to controls (30.0 (2.0) mumol/l cells/h). Mean Km (ZT) was not significantly altered in HD or CAPD (HD: 6.1 (1.6) microM; CAPD: 5.5 (0.7) microM; control: 5.1 (0.9) microM). The sensitivity of choline transport to the inhibitors tested was not altered in HD. 1.0 mM quinine, 2.0 mM NEM and 1.0 mM HC-3 caused 75-90% inhibition of transport in both HD and controls. For inhibition of ZT influx of 25 microM choline the mean IC50 of quinine was 90 (9) microM in HD and 101 (13) microM in controls (n.s.). The ZT influx of 200 microM choline was not altered by any of the polyamines at concentrations up to 1.0 mM. CONCLUSIONS: Membrane choline transport in CRF remains protein-mediated and exhibits normal substrate and inhibitor affinities; high values of Vmax seem to occur through increased surface expression of an active normal choline transporter. Increases in plasma polyamines cannot explain the choline transport changes in CRF.

Modelling and costing the consequences of using an ACE inhibitor to slow the progression of renal failure in type I diabetic patients.

Antihypertensive drugs slow the progressive decline in renal function seen in patients with insulin-dependent diabetes and nephropathy. In a recent study, the ACE inhibitor captopril protected against this deterioration in renal function. We developed an economic model to analyse the cost impact of ACE inhibitor treatment on progression to endstage renal failure (ESRF) in diabetic patients over 4 years. Two scenarios were compared: one describing the progression of a cohort of 1000 patients receiving 25 mg captopril three times daily, and the other for an equivalent cohort without such prophylactic treatment. Previously published data were used to estimate the transition rates for each stage from the onset of renal failure until death. All direct costs were discounted by an annual rate of 6%, and were subjected to sensitivity analysis. The discounted cost saving of ACE inhibitor treatment for a cohort of 1000 patients was estimated as 0.95 million pounds over 4 years. Under sensitivity analysis, these results were very robust to variations in the costs of ESRF treatment. Prophylactic treatment with ACE inhibitors was predicted to provide substantial increases in life expectancy and reduction in the incidence of ESRF, while also providing significant economic savings.

Non-invasive cardiac investigations in patients awaiting renal transplantation.

Patients with chronic renal failure undergoing renal transplantation have a high prevalence of cardiovascular disease. Invasive investigation may identify those at risk of cardiac death during or after renal transplantation, but which patients should undergo cardiac catheterization is currently not clear. In 95 patients awaiting renal transplantation we assessed the ability of echocardiography and exercise electrocardiography to identify patients at risk of cardiac death. Echocardiography identified impaired left ventricular (LV) systolic function in 20%, severe in 8%. Of the patients with severe LV dysfunction, 25% died before transplantation. Of those undergoing exercise electrocardiography, 44% did not achieve 85% of maximum predicted heart rate. No coronary artery disease requiring intervention was identified by exercise testing. These findings indicate that echocardiography, but not exercise electrocardiography, should be part of the assessment for renal transplantation.