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Biomedical subjects

David W Johnson

Publications and source records attributed to David W Johnson.

At least 55 records · Page 3Linked to original sources
PubMed2005

Higher rate and earlier peritonitis in Aboriginal patients compared to non-Aboriginal patients with end-stage renal failure maintained on peritoneal dialysis in Australia: analysis of ANZDATA.

BACKGROUND: Aboriginal patients maintained on peritoneal dialysis (PD) have a higher rate of technique failure than any other racial group in Australia. Peritonitis accounts for the bulk of these technique failures, but it is uncertain whether the increased risk of peritonitis in Aboriginal patients was independent of associated comorbid conditions, such as diabetes mellitus. METHODS: Using data collected by the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA), peritonitis rates and time to first peritonitis were compared between Aboriginal (n = 238) and non-Aboriginal patients (n = 2924) commencing PD in Australia between 1 April 1999 and 31 March 2003. RESULTS: Aboriginal PD patients were younger, and had a higher incidence of diabetes than their non-Aboriginal counterparts. Mean peritonitis rates were significantly higher among Aboriginal (1.15 episodes/year; 95% confidence interval (CI): 1.03-1.28) than non-Aboriginal patients (0.60 episodes/year; 95% CI: 0.57-0.62, P < 0.05). Using multivariate negative binomial regression, independent predictors of higher peritonitis rates include Aboriginal racial origin (adjusted odds ratio 1.78; 95% CI: 1.45-2.19), obesity, age and absence of a recorded dialysate : plasma creatinine ratio (D/P creatinine) measurement. Aboriginal racial origin was also associated with a shorter median time to first peritonitis (9.9 vs 19.3 months, P < 0.05), which remained statistically significant in a multivariate Cox proportional hazards model (adjusted hazard ratio 1.76; 95% CI: 1.47-2.11, P < 0.05). CONCLUSION: Aboriginal and obese PD patients have a higher rate of peritonitis and a shorter time to first peritonitis, independent of demographic and comorbid factors. Further investigation of the causes of increased peritonitis risk in Aboriginal patients is needed.

Adolescent↗
PubMed2005

Impact of obesity on renal transplant outcomes.

Obesity is a frequent and important consideration to be taken into account when assessing patient suitability for renal transplantation. In addition, posttransplant obesity continues to represent a significant challenge to health care professionals caring for renal transplant recipients. Despite the vast amount of evidence that exists on the effect of pretransplant obesity on renal transplant outcomes, there are still conflicting views regarding whether obese renal transplant recipients have a worse outcome, in terms of short- and long-term graft survival and patient survival, compared with their non-obese counterparts. It is well established that any association of obesity with reduced patient survival in renal transplant recipients is mediated in part by its clustering with traditional cardiovascular risk factors such as hypertension, dyslipidaemia, insulin resistance and posttransplant diabetes mellitus, but what is not understood is what mediates the association of obesity with graft failure. Whether it is the higher incidence of cardiovascular comorbidities jeopardising the graft or factors specific to obesity, such as hyperfiltration and glomerulopathy, that might be implicated, currently remains unknown. It can be concluded, however, that pre- and posttransplant obesity should be targeted as aggressively as the more well-established cardiovascular risk factors in order to optimize long-term renal transplant outcomes.

Body Mass Index↗
PubMed2005

Activation of ERK in renal fibrosis after unilateral ureteral obstruction: modulation by antioxidants.

BACKGROUND: A recent in vitro model of oxidative stress-induced renal fibrosis demonstrated that activated or phosphorylated extracellular signal-regulated protein kinase (pERK) played a role in apoptosis of renal fibroblasts, but not tubular epithelium where it promoted cell growth and survival. The present study utilized an in vivo model of renal fibrosis after unilateral ureteral obstruction (UUO) to examine the relationship between pERK, apoptosis, proliferation, and differentiation in renal fibroblast and tubular epithelial cells, in comparison with the in vitro results. METHODS: UUO was induced in rats for 0 (controls, untreated), 6, and 24 hours, 2, 4, and 7 days (N= 4), and tissue analyzed for fibrotic characteristics using microscopy and special stains, Western immunoblots and reverse transcription-polymerase chain reaction (RT-PCR). Controls and UUO animals were also treated with vitamin E, N-acetylcysteine (NAC), or fluvastatin to assess any antioxidant effect on attenuation of fibrosis and pERK expression. RESULTS: Azan stain and alpha-smooth muscle actin (alpha-SMA), collagen III, and fibronectin expression confirmed development of UUO-induced fibrosis. Oxidative stress markers heme oxygenase-1 (HO-1) and 8-hydroxy-2'-deoxyguanosine (8-OHdG) confirmed oxidative stress at all UUO time points. Tubular epithelial and interstitial mitosis and apoptosis were significantly increased over controls at 2 to 7 days after UUO (P < 0.01). The pERK/ERK ratio increased significantly at 1 to 7 days of UUO in comparison with controls (three- to fivefold, P < 0.05). There was a significant spatiotemporal correlation between pERK and tubular epithelial proliferation (P < 0.001). pERK occasionally colocalized with apoptotic cells (dual labeling) in the interstitium but not in the tubular epithelium. Fluvastatin was the only treatment that attenuated fibrosis (decreased alpha-SMA, fibronectin, tubular epithelial apoptosis) and it also significantly decreased expression of 8-OHdG at 2 and 7 days (P < 0.05). It was associated with decreased pERK at 7 days, compared with UUO alone (P < 0.05). CONCLUSION: Promotion of tubular epithelial proliferation and survival, and interstitial cell apoptosis, may minimize renal fibrosis after UUO. In the present study, both were linked spatially and temporally with increased pERK expression. Fluvastatin treatment attenuated UUO-induced fibrosis via an antioxidant and pERK-related mechanism.

Animals↗
PubMed2005

Thrombin stimulates proinflammatory and proliferative responses in primary cultures of human proximal tubule cells.

BACKGROUND: Fibrin deposition is frequently observed within the tubulointerstitium in various forms of chronic renal disease. This suggests the presence of active components of the coagulation pathway, which may contribute to the progressive deterioration in renal function. The aim of this study was to investigate the proinflammatory and fibroproliferative effects of the coagulation protease thrombin on human proximal tubular cells (PTC) in culture. METHODS: Primary cultures of PTC were established from normal kidney tissue and grown under serum-free conditions with or without thrombin or the protease-activated receptor (PAR) activating peptides TFLLRN-NH(2), SLIGKV-NH(2), and SFLLRN-NH(2) (100 to 400 micromol/L). DNA synthesis (thymidine incorporation), intracellular Ca(2+) mobilization (fura-2 fluorimetry), fibronectin secretion [enzyme-linked immunosorbent assay (ELISA), immunoblotting], monocyte chemoattractant protein-1 (MCP-1) secretion (ELISA), and transforming growth factor-beta1 (TGF-beta1) secretion (ELISA) were measured. Reverse transcription-polymerase chain reaction (RT-PCR) was used to assess PAR mRNA expression in these cells. RESULTS: Thrombin enhanced DNA synthesis, fibronectin secretion, MCP-1 secretion, and TGF-beta1 secretion in a concentration-dependent manner. Cell injury [lactate dehydrogenase (LDH) release] and cellular protein levels were unaffected. RT-PCR showed that cultures of PTC expressed mRNA transcripts for the thrombin receptors PAR-1 and PAR-3, but not PAR-4. Thrombin and each of the PAR activating peptides enhanced intracellular calcium mobilization. However, the other effects of thrombin were only fully reproduced by the PAR-2-specific peptide, SLIGKV-NH(2), only partially by SFLLRN-NH(2), (a PAR-1 peptide that can activate PAR-2), and not at all by the PAR-1-specific peptide, TFLLRN-NH(2). Thrombin-induced DNA synthesis, fibronectin, and MCP-1 secretion were unaffected by a TGF-beta neutralizing antibody, the matrix metalloproteinase (MMP) inhibitor, GM6001 and the epidermal growth factor (EGF) receptor kinase inhibitor AG1478. CONCLUSION: Thrombin initiates both proinflammatory and fibroproliferative responses in human PTC. These responses which are dependent on its protease activity appear not to be mediated by PAR-1 activation, the autocrine action of thrombin-induced TGF-beta1 secretion, MMP activation, or EGF receptor transactivation. The proinflammatory and fibroproliferative actions of thrombin on human PTC may help explain the extent of tubulointerstitial fibrosis observed in kidney diseases where fibrin deposition is evident.

Calcium Signaling↗
PubMed2005

Obesity is associated with worsening cardiovascular risk factor profiles and proteinuria progression in renal transplant recipients.

Obesity is associated with adverse cardiovascular (CV) parameters and may be involved in the pathogenesis of allograft dysfunction in renal transplant recipients (RTR). We sought the spectrum of body mass index (BMI) and the relationships between BMI, CV parameters and allograft function in prevalent RTR. Data were collected at baseline and 2 years on 90 RTR (mean age 51 years, 53% male, median transplant duration 7 years), categorized by BMI (normal, BMI < or = 24.9 kg/m2; pre-obese, BMI 25-29.9 kg/m2; obese, BMI > or = 30 kg/m2). Proteinuria and glomerular filtration rate (eGFR(MDRD)) were determined. Nine percent RTR were obese pre-transplantation compared to 30% at baseline (p < 0.001) and follow-up (25 +/- 2 months). As BMI increased, prevalence of metabolic syndrome and central obesity increased (12 vs 48 vs 85%, p < 0.001 and 3 vs 42 vs 96%, p < 0.001, respectively). Systolic blood pressure, fasting blood glucose and lipid parameters changed significantly with BMI category and over time. Proteinuria progression occurred in 65% obese RTR (23 (13-59 g/mol creatinine) to 59 (25-120 g/mol creatinine)). BMI was independently associated with proteinuria progression (beta 0.01, p = 0.008) but not with changing eGFR(MDRD.) In conclusion, obesity is common in RTR and is associated with worsening CV parameters and proteinuria progression.

Adult↗
PubMed2005

New developments in social interdependence theory.

Social interdependence theory is a classic example of the interaction of theory, research, and practice. The premise of the theory is the way that goals are structured determines how individuals interact, which in turn creates outcomes. Since its formulation nearly 60 years ago, social interdependence theory has been modified, extended, and refined on the basis of the increasing knowledge about, and application of, the theory. Researchers have conducted over 750 research studies on the relative merits of cooperative, competitive, and individualistic efforts and the conditions under which each is appropriate. Social interdependence theory has been widely applied, especially in education and business. These applications have resulted in revisions of the theory and the generation of considerable new research. The authors critically analyze the new developments resulting from extensive research on, and wide-scale applications of, social interdependence theory.

Codependency, Psychological↗
PubMed2005

Electrocardiogram interpretation and management in a pediatric emergency department.

OBJECTIVES: To determine the accuracy of electrocardiogram (ECG) interpretation by pediatric emergency physicians through comparison with a pediatric cardiologist and to determine the intrarater and interrater reliability for pediatric emergency physicians and cardiologists. METHODS: This was a prospective cohort study in which pediatric emergency physicians ordering an ECG completed a standardized questionnaire. The same emergency physician, a second emergency physician, and a pediatric cardiologist also completed the questionnaire for all ECGs at a later time. A randomly selected subset of ECGs was also interpreted by the same cardiologist and a second pediatric cardiologist. Major outcome variables were (1) whether the ECG was normal or abnormal, and if abnormal, (2) whether the abnormality represented a minor or major concern, and (3) whether the ECG warranted referral to a pediatric cardiologist. RESULTS: For pediatric emergency physicians, the intrarater and interrater kappa values were 0.56 and 0.24 for the presence of an abnormality, 0.49 and 0.36 for level of concern, and 0.63 and 0.25 for need of cardiology follow-up. For pediatric cardiologists, the intrarater and interrater kappa values were 0.82 and 0.92 for the presence of an abnormality, 0.71 and 1.00 for level of concern, and 0.82 and 0.91 for need of cardiology follow-up. A comparison of the initial emergency physician and cardiologist interpretations yielded kappa values of 0.42 for the presence of an abnormality, 0.16 for level of concern, and 0.31 for need of cardiology follow-up. CONCLUSIONS: When compared with interpretation by a pediatric cardiologist, ECG interpretation by pediatric emergency physicians was relatively inaccurate; intrarater and interrater agreement among emergency physicians was good and poor, respectively, and the intrarater and interrater agreement among pediatric cardiologists was excellent.

Adolescent↗
PubMed2005

Chronic kidney disease--management update.

BACKGROUND: Chronic kidney disease (CKD), defined as a glomerular filtration rate less than 60 mL/min/1.73 m2 and/or evidence of kidney damage for a period of at least 3 months, is an increasingly common, serious and under-recognised condition. A recent population study demonstrated that one in every 6 Australian adults has CKD (of which the vast majority are unaware). OBJECTIVE: This article aims to provide timely information to health professionals about how to classify and manage CKD. DISCUSSION: Management of CKD involves regular monitoring of cardiovascular and renal risk factors, identifying and treating common CKD complications, and avoiding medications that may worsen CKD. Early detection and timely appropriate management of CKD (especially with respect to blood pressure control) will substantially reduce kidney failure progression and cardiovascular risk by up to 50%.

Adult↗
PubMed2004

Disseminated pyogenic Mycoplasma pneumoniae infection in a renal transplant recipient, detected by broad-range polymerase chain reaction.

Although extrapulmonary manifestations of Mycoplasma pneumoniae infection are generally immune-mediated, disseminated infections occasionally occur. We describe a renal transplant recipient who developed disseminated pyogenic M. pneumoniae infection that was detected by broad-range polymerase chain reaction and that manifested by prosthetic arterial graft infection, psoas abscess, and septic arthritis.

Adult↗
PubMed2004

A randomized trial of a single dose of oral dexamethasone for mild croup.

BACKGROUND: The benefits of dexamethasone treatment for moderate-to-severe croup are well established. However, most children with croup have mild symptoms, and it is unknown whether they would derive the same degree of benefit from dexamethasone treatment as children with more severe disease. METHODS: We conducted a double-blind trial at four pediatric emergency departments in which 720 children with mild croup were randomly assigned to receive one oral dose of either dexamethasone (0.6 mg per kilogram of body weight) or placebo. The children had mild croup, as defined by a score of < or =2 on the croup scoring system of Westley et al. The primary outcome was a return to a medical care provider for croup within seven days after treatment. The secondary outcome was the presence of ongoing symptoms of croup on days 1, 2, and 3 after treatment. Other outcomes included economic costs, hours of sleep lost by the child, and stress on the part of the parent in relation to the child's illness. RESULTS: Baseline clinical characteristics were similar in the two groups. Return to medical care was significantly lower in the dexamethasone group (7.3 percent vs. 15.3 percent, P<0.001). In the dexamethasone group, there was quicker resolution of croup symptoms (P=0.003), less lost sleep (P<0.001), and less stress on the part of the parent (P<0.001). CONCLUSIONS: For children with mild croup, dexamethasone is an effective treatment that results in consistent and small but important clinical and economic benefits. Although the long-term effects of this treatment are not known, our data support the use of dexamethasone in most, if not all, children with croup.

Administration, Oral↗
PubMed2004

The effect of oral iron admiinistration on mycophenolate mofetil absorption in renal transplant recipients: a randomized, controlled trial.

BACKGROUND: Oral iron supplements are frequently prescribed to renal transplant recipients in the early posttransplant period. A recent trial in seven healthy volunteers demonstrated a significant 91% reduction in mycophenolate mofetil (MMF) absorption when coadministered with oral iron. However, the effect of iron on MMF absorption in renal transplant patients has not been studied. METHODS: An open-label, randomized, controlled trial was undertaken in which new renal transplant recipients were randomly allocated to receive iron supplements with a morning dose of MMF, iron supplements given 4 hr after MMF at midday, or no iron supplements. Blood samples were taken for estimation of mycophenolic acid (MPA) area under the curve (AUC) at day 5 posttransplant. The primary endpoint was the day 5 MPA AUC, with secondary endpoints including acute rejection and MMF toxicity in the first 4 weeks posttransplant. Prospective power calculations indicated that a minimum of 13 patients in each group would be required to have a 90% probability of detecting a clinically significant reduction (10 mg/hr/L) in MPA AUC for iron-treated patients. RESULTS: Forty patients completed the study. There were no differences in baseline demographic data between the groups. The mean+/-standard deviation MPA AUC measurements for the groups receiving no iron (n=13), iron and MMF together (n=14), and iron and MMF spaced apart (n=13) were 34.5+/-8.7, 33.7+/-11.4, and 32.1+/-8.1 microg/hr/mL, respectively (P=0.82). Rates of acute rejection, cytopenia, infection, and gastrointestinal intolerance were comparable between the groups. CONCLUSIONS: There is no significant effect of oral iron supplements on MMF absorption as determined by measured blood concentrations. The practice of routinely giving oral iron in such patients seems safe from an immunosuppression drug-interaction standpoint.

Adult↗
PubMed2004

Quantification of free mycophenolic acid and its glucuronide metabolite in human plasma by liquid-chromatography using mass spectrometric and ultraviolet absorbance detection.

The immunosuppressant drug mycophenolic acid (MPA) and its major metabolite, mycophenolic acid glucuronide (MPAG), are highly bound to albumin. An HPLC-tandem-MS (HPLC/MS/MS) and an HPLC-UV assay were developed to measure free (unbound) concentrations of MPA and MPAG, respectively. Ultrafiltrate was prepared from plasma (500 microl) by ultrafiltration at 3000 x g for 20 min (20 degrees C). Both MPA and MPAG were isolated from ultrafiltrate (100 microl) by acidification and C18 solid-phase extraction. Free MPA was measured by electrospray tandem mass spectrometry using selected reactant monitoring (MPA: m/z 338.2--> 206.9) in positive ionisation mode. Chromatography was performed on a PFPP column (50 mm x 2 mm, 5 microm). Total analysis time was 7 min. The assay was linear over the range 1-200 microg/l with a limit of quantification of 1 microg/l. The inter-day accuracy and imprecision of quality controls (7.5, 40, 150 microg/l) were 94-99% and < 7%, respectively. Free MPAG was chromatographed on a C18 Nova-Pak column (150 mm x 3.9 mm, 5 microm) using a binary gradient over 20 min. The eluent was monitored at 254 nm. The assay was linear over the range 1-50 mg/l with the limit of quantification at 2.5 mg/l. The inter-day accuracy and imprecision of quality controls (5, 20, 45 mg/l) was 101-107% and < 8% (n = 4), respectively. For both methods no interfering substances were found in ultrafiltrate from patients not receiving MPA. The methods described have a suitable dynamic linear range to facilitate the investigation of free MPA and MPAG pharmacokinetics in transplant patients. Further, this is the first reported HPLC-UV method to determine free MPAG concentrations.

Chromatography, High Pressure Liquid↗
PubMed2004

Synthesis of dicarboxylic acylcarnitines.

Syntheses of malonyl, methylmalonyl, succinyl, glutaryl, methylglutaryl, dodecanedioyl and hexadecanedioyl carnitines are described. The dicarboxylic acylcarnitines were prepared from eight equivalents of cyclic anhydride or isopropylidene ester of the dicarboxylic acid and carnitine chloride in trifluoroacetic acid solution. Long chain dicarboxylic acylcarnitines were additionally purified by partitioning between water and n-butanol. Stable isotope labeled analogs, containing 3, 6 or 9 deuterium atoms, were also prepared. They are for use as standards in the electrospray ionization tandem mass spectrometric analysis of dicarboxylic acylcarnitines in samples from patients with inherited disorders of fatty acid oxidation.

Carnitine↗
PubMed2004

Glandular trichome extracts from Medicago sativa deter settling by the potato leafhopper Empoasca fabae.

Extracts of glandular trichomes from Medicago sativa were tested for their ability to disrupt the settling behavior of the potato leafhopper, Empoasca fabae. Erect and procumbent glandular trichomes were mechanically isolated from stem sections of resistant genotype "G98A," and nonglandular trichomes were collected from susceptible cultivar "Ranger." Isolated trichomes were extracted with chloroform, acetone, and ethanol, and the resulting crude extracts were applied to the surface of a sachet containing an artificial diet. Leafhoppers were offered a two-way choice between crude trichome extracts from G98A and Ranger. All three of G98A solvent extracts caused various degrees of diet rejection, resulting in the crude Ranger trichome extracts being preferred over G98A extracts. Overall, the fewest leafhoppers settled on the ethanolic extracts. Additional bioassays documented a dose response associated with G98A ethanolic extracts when compared with Ranger trichome extracts and a solvent control. No difference in preference behavior was detected between Ranger trichome extracts and a solvent control. Gas chromatography-mass spectrometry analysis revealed a homologous series of nonvolatile fatty acid amides C(n)H(2n+1)NO (n = 19-23) unique to G98A glandular trichome extracts.

Amides↗
PubMed2004

Bioactivity of lipophilic metabolites from glandular trichomes of Medicago sativa against the potato leafhopper.

Medicago sativa cv. G98A is highly resistant to the potato leafhopper, Empoascafabae. Glandular trichome extracts from G98A were fractionated using flash chromatography and tested for settling deterrency against the potato leafhopper. A fraction of intermediate polarity exhibited strong, dose-dependent deterrency when applied to the surface of an artificial diet sachet. Deterrency was not detected, however, when the fraction was applied to the internal surface of the sachet membrane (i.e., when contact was limited to only the leafhoppers' stylets). Major components of the highly deterrent fraction, determined by gas chromatography-mass spectrometry, were a homologous series of fatty acid amides C(n)H(2n+1)NO (n = 19-23) and trace components were 12:0, 13:0, 14:0, 15:0, 16:0, 17:0, 18:0, and possibly 18:1 free fatty acids. Deterrency declined slightly, but was still strong, after fatty acids were removed from crude extracts. When the crude extracts were separated further, a fraction containing only the fatty acid amides was also deterrent. Activity increased when this fraction was supplemented with authentic (C12:0 through C18:0, and C18:1) free fatty acids. However, the authentic free fatty acids were not deterrent when tested without the lipophilic amides. Fatty acid amides and free fatty acids in trichomes of M. sativa G98A may synergize and together function in deterring settling by the potato leafhopper.

Amides↗
PubMed2004

Predictors of baseline peritoneal transport status in Australian and New Zealand peritoneal dialysis patients.

BACKGROUND: Factors that predict peritoneal transport status in peritoneal dialysis (PD) patients are poorly understood. The aim of the present study is to determine these factors in Australian and New Zealand incident PD patients. METHODS: The study included all patients on the Australian and New Zealand Dialysis and Transplant Registry who started PD therapy between April 1, 1991, and March 31, 2002, and underwent a peritoneal equilibration test (PET) within the first 6 months. Predictors of peritoneal transport category and dialysate-plasma creatinine ratio at 4 hours (D-P Cr 4h) were assessed by multivariate ordinal logistic regression and multiple linear regression, respectively. RESULTS: A total of 3,188 patients were studied. Mean D-P Cr 4h was 0.69 +/- 0.13. High transport status was associated with older age (adjusted odds ratio [OR], 1.08 for each 10 years; 95% confidence interval [CI], 1.03 to 1.13), Maori and Pacific Islander racial origin (OR, 1.48; 95% CI, 1.13 to 1.94), and normal body mass index (BMI; < 18.5 kg/m2: OR, 0.90; 95% CI, 0.65 to 1.24; BMI of 18.5 to 25 kg/m2: OR, 1 [reference]; BMI of 25 to 30 kg/m2: OR, 0.81; 95% CI, 0.70 to 0.95; BMI > 30 kg/m2: OR, 0.71; 95% CI, 0.58 to 0.86), but was not independently predicted by sex, diabetes, other comorbid diseases, smoking, previous hemodialysis therapy or transplantation, or residual renal function. Similar results were found when peritoneal permeability was modeled as a continuous variable (D-P Cr 4h). CONCLUSION: In Australian and New Zealand PD patients, higher peritoneal transport status is independently associated with racial origin, older age, and lower BMI. The diversity of peritoneal transport characteristics in different ethnic populations suggests that additional validation of PET measurements in various racial groups and study of their relationship to patient outcomes are warranted.

Adult↗
PubMed2004

Erythropoietin protects against ischaemic acute renal injury.

BACKGROUND: Erythropoietin (EPO) has recently been shown to exert important cytoprotective and anti-apoptotic effects in experimental brain injury and cisplatin-induced nephrotoxicity. The aim of the present study was to determine whether EPO administration is also renoprotective in both in vitro and in vivo models of ischaemic acute renal failure. METHODS: Primary cultures of human proximal tubule cells (PTCs) were exposed to either vehicle or EPO (6.25-400 IU/ml) in the presence of hypoxia (1% O(2)), normoxia (21% O(2)) or hypoxia followed by normoxia for up to 24 h. The end-points evaluated included cell apoptosis (morphology and in situ end labelling [ISEL], viability [lactate dehydrogenase (LDH release)], cell proliferation [proliferating cell nuclear antigen (PCNA)] and DNA synthesis (thymidine incorporation). The effects of EPO pre-treatment (5000 U/kg) on renal morphology and function were also studied in rat models of unilateral and bilateral ischaemia-reperfusion (IR) injury. RESULTS: In the in vitro model, hypoxia (1% O(2)) induced a significant degree of PTC apoptosis, which was substantially reduced by co-incubation with EPO at 24 h (vehicle 2.5+/-0.5% vs 25 IU/ml EPO 1.8+/-0.4% vs 200 IU/ml EPO 0.9+/-0.2%, n = 9, P<0.05). At high concentrations (400 IU/ml), EPO also stimulated thymidine incorporation in cells exposed to hypoxia with or without subsequent normoxia. LDH release was not significantly affected. In the unilateral IR model, EPO pre-treatment significantly attenuated outer medullary thick ascending limb (TAL) apoptosis (EPO 2.2+/-1.0% of cells vs vehicle 6.5+/-2.2%, P<0.05, n = 5) and potentiated mitosis (EPO 1.1+/-0.3% vs vehicle 0.5+/-0.3%, respectively, P<0.05) within 24 h. EPO-treated rats exhibited enhanced PCNA staining within the proximal straight tubule (6.9+/-0.7% vs vehicle 2.4+/-0.5% vs sham 0.3+/-0.2%, P<0.05), proximal convoluted tubule (2.3+/-0.6% vs vehicle 1.1+/-0.3% vs sham 1.2+/-0.3%, P<0.05) and TAL (4.7+/-0.9% vs vehicle 0.6+/-0.3% vs sham 0.3+/-0.2%, P<0.05). The frequency of tubular profiles with luminal cast material was also reduced (32.0+/-1.6 vs vehicle 37.0+/-1.3%, P = 0.05). EPO-treated rats subjected to bilateral IR injury exhibited similar histological improvements to the unilateral IR injury model, as well as significantly lower peak plasma creatinine concentrations than their vehicle-treated controls (0.04+/-0.01 vs 0.21+/-0.08 mmol/l, respectively, P<0.05). EPO had no effect on renal function in sham-operated controls. CONCLUSIONS: The results suggest that, in addition to its well-known erythropoietic effects, EPO inhibits apoptotic cell death, enhances tubular epithelial regeneration and promotes renal functional recovery in hypoxic or ischaemic acute renal injury.

Animals↗