One of the main causes of early graft dysfunction in kidney transplantation is ischaemia reperfusion (I/R) injury. This unavoidable event occurs immediately when oxygenated blood is re-introduced into the transplanted kidney. Its severity is influenced by many predetermined factors. However, the condition under which an organ is preserved has a significant bearing on the outcome. Traditionally, organs are preserved using hypothermic temperatures, to reduce metabolism and the requirement for oxygen. Although practical and simple, hypothermic conditions are not entirely favourable and over time the depletion of energy substrates causes substantial cellular injury. This is thought to be a particular problem in kidneys from marginal donors, which are often exposed to a period of warm ischaemia (WI) prior to retrieval. The aim of this thesis was to determine the effects of varying degrees of the combined insults of warm and cold ischaemic injury and to develop a technique of normothermic perfusion (NP) to reduce ischaemic injury. The effects were assessed using ex-vivo and in-vivo porcine kidney models before translation of NP into clinical practice for marginal donor kidneys. This research demonstrated that prolonging the hypothermic preservation period after a minimal and a substantial degree of WI injury increased the severity of acute I/R injury and graft dysfunction. A short period of NP after hypothermic preservation was able to resuscitate the kidney, replenish ATP and reverse some of the detrimental effects of cold ischaemic injury. When translated into an autotransplant model, NP was found to be a safe and feasible method of preservation. NP was then adapted for use in clinical practice for kidneys from marginal donors. This first in man clinical series of 15 cases has demonstrated the safety and feasibility of NP for marginal kidneys. Although, the high rate of initial graft function is notable, further comparative studies are required to assess the effects on delayed graft function.

The enzymes prostaglandin synthetase (PGS) and lipoxygenase can cooxidise a variety of xenobiotics to reactive intermediates during the metabolism of arachidonic acid (AA). PGS exhibited a gradient of activity within the kidney which was greatest in the papilla and least in the cortex. Rabbit and rat renal microsomes metabolised the model compound, tetramethylphenylenediamine (TMPD), in the presence of AA by pathways which were predominantly PGS and lipoxygenase-dependent, respectively. Therefore, both enxymes may play a role in the development of site-specific nephrotoxicity within the kidney. The model papillotoxin 2-bromoethanamine (2-BEA) which exhibits target selective toxicity for the renal papilla, was found to be significantly more toxic to medullary interstitial cells than to proximal tubule cells in culture. Toxicity was enhanced significantly by AA whereas inhibitors of cyclooxygenase (indomethacin, aspirin), prostaglandin hydroperoxidase (propylthiouracyl) and lipoxygenase (nordihydrogauaretic acid) all significantly decreased 2-BEA toxicity. This suggests that toxicity is mediated either by the hydroperoxidase component of PGS or by lipoxygenase. Thromboxane A₂ (TxA₂) is thought to play a pivotal role in cyclosporin A (CsA) induced nephrotoxicity. Administration of a thromboxane synthetase inhibitor (TSI) normalised TxB₂ excretion but only partially protected against other factors involved. However, treatment with angiotensin converting enzyme inhibitor either alone or in combination with TSI did not affect CsA nephrotoxicity. Tubular toxicity, manifest as N-acetyl-β-D-glucosaminidase (NAG) enzymuria, glycosuria, vacuolation, calcification and chronic tubule damage, may contribute to the CsA-induced reduction in renal function. In addition to protecting against CsA-induced nephrotoxicity, the administration of TSI to CsA-treated rats also partially reversed pre-existing renal damage.

The present studies investigated the relationship between altered renal carbohydrate intermediary metabolism and kidney functional and structural changes in the adult Spraque-Dawley rat. Both the acute (upto 28 days) and chronic (60-120 days) diabetic states were invstigated. The single intraperitoneal injection of streptozotocin at a dose of 45mg/kg body weight produced a stable, non-ketotic, non-insulin dependent and reproducible diabetic state. Compared to age matched control animals (AMC), diabetic animals (DA) demonstrated a progressive increase in mean UFR, plasma glucose, creatinine, glycosuria values and urea clearance rate over the experimental course while creatinine clearance (CCR) fell from day 21 onwards reaching 50% of AMC values by day 120. Changes in renal and hepatic metabolite concentrations were apparent after 4 days of diabetes and two patterns emerged. Renal and hepatic glucose, glocuse-1-phosphate and β-hydroxybutyric acid concentrations progressively increased over the 120 days experimental period while reduced concentrations of glycolytic and other metabolic intermediates, namely, glucose-60-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate, glyceraldehyde-3-phosphate, dihydroxyacetone 3- phosphate and malonyl-CoA concentrations were present. Increased concentrations of BHBA in both the liver and kidney was accompanied by the progressive reduction of malonyl-CoA. Since gluconeognesis is favoured at the expense of glycolysis in these diabetic animals, the absence of phosphofructokinase activity may be explained by a decreased concentration of fructose-6-phosphate. Renal gluconeogenic enzymes such as fructose-1,6-phosphatase were mainly located in the kidney cortex, predominantly located in the proximal tubular epithelium and that glycolytic enzymes such as hexokinase occurred mainly in the kidney medulla, restricted essentially in distal segments. Histological examination demonstrated an increasing degree of renal clear cell changes affecting from 5-20% of cells noted from day 10 to day 120, respectively in the cortical renal tubules. In addition acute pyelonephritis was also observed in all diabetic animals on days 90 and 120.

The studies in this thesis concern alloantibody responses against MHC class I antigens. These antibodies are induced by blood transfusions and strongly associated with clinical kidney allograft rejection. These findings were: 1. Cytotoxic antibodies in 11 multiparous patients, who had become broadly sensitised by blood transfusions, were of IgG class and directed to HLA class I antigens. In all patients, some of these antibodies were directed against class I specificities expressed by the partner by whom the patient was parous. 2. In high responder multiparous rats, humoral responses against paternal MHC class I antigens reencountered in blood transfusions given after pregnancy were suppressed. In contrast, minor histocompatibility antigens shared between the paternal and later blood donor strains enhanced anti-MHC class I antibody responses. 3. In multiparous rats, anti-paternal antibodies stimulated by pregnancy were not influenced by materno-paternal disparities at MHC class II or minor antigenic loci, and were directed to conventional MHC class I epitopes. 4. In high responder rats, there was no evidence for either humoral or cellular tolerance to non-inherited maternal MHC antigens. 5. In high responder rats pre-treated with blood transfusions and concomitant cyclosporin A, subsequent antibody responses to third party MHC class I antigens encountered in challenge transfusions, given without cyclosporin A, were suppressed only when minor histocompatibility antigens were shared between the initial and challenge transfusions. 6. Three drugs:- cyclosporin A, FK506 and rapamycin abrogated anti-MHC class I alloantibody responses to blood transfusions by naive rats and, at the same time, induced humoral tolerance. None of these drugs, however, inhibited either ongoing, alloantibody synthesis or humoral anamnestic responses in high responder rats with established humoral immunity.

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Hyperhomocysteinemia, a condition of elevated blood homocysteine (Hcy) level, is an independent risk factor for cardiovascular disease. Folic acid supplementation can effectively reduce blood Hcy levels. Recent studies have demonstrated that hyperhomocysteinemia is also associated with kidney disease. However, the underlying mechanisms remain unclear. The overall objective of the study was to investigate the biochemical and molecular mechanisms of Hcy-induced kidney injury and the effect of folic acid supplementation on Hcy-induced kidney injury. Hyperhomocysteinemia was induced in Sprague-Dawley rats by feeding a high-methionine diet for 12 weeks. An elevation of serum total Hcy level was observed in hyperhomocysteinemic rats. Hyperhomocysteinemia-induced superoxide anion production via nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation resulted in oxidative stress in the kidney. Reduction of oxidative stress by inhibiting superoxide anion production effectively ameliorated hyperhomocysteinemia-induced kidney injury. Inflammatory responses such as increased chemokine expression have been implicated as one of the mechanisms of kidney disease. Monocyte chemoattractant protein-1 (MCP-1) is a potent chemokine that is involved in the inflammatory response in kidney disease. Nuclear factor-kappa B (NF-kappaB) plays an important role in upregulation of MCP-1 expression. We investigated the effect of hyperhomocysteinemia on MCP-1 expression and the molecular mechanism responsible for such an effect in rat kidneys as well as in human kidney proximal tubular cells.

No description available.

No description available.

Background: Survivors of severe acute kidney injury remain at high risk of death well-after apparent recovery from the initial event. Methods: We conducted a cohort study of hospitalized adults in Ontario from 1996 to 2008 with acute kidney injury who received temporary dialysis and survived for 90 days following discharge independent from dialysis. The exposure was nephrology follow-up. We used propensity scores to match individuals with early nephrology follow-up to those without. The primary outcome was time to mortality. Results : We identified 3877 patients with acute kidney injury who met the eligibility criteria. A total of 1583 patients had nephrology follow. The incidence of all-cause mortality was lower in those with early nephrology follow-up as compared to those without early follow-up (8.4 vs. 10.6 per 100 person-years, HR 0.76 (95% CI 0.62-0.93)). Conclusions: Nephrology follow-up after hospitalization with acute kidney injury and temporary dialysis was associated with improved survival.

Background: Survivors of severe acute kidney injury remain at high risk of death well-after apparent recovery from the initial event. Methods: We conducted a cohort study of hospitalized adults in Ontario from 1996 to 2008 with acute kidney injury who received temporary dialysis and survived for 90 days following discharge independent from dialysis. The exposure was nephrology follow-up. We used propensity scores to match individuals with early nephrology follow-up to those without. The primary outcome was time to mortality. Results : We identified 3877 patients with acute kidney injury who met the eligibility criteria. A total of 1583 patients had nephrology follow. The incidence of all-cause mortality was lower in those with early nephrology follow-up as compared to those without early follow-up (8.4 vs. 10.6 per 100 person-years, HR 0.76 (95% CI 0.62-0.93)). Conclusions: Nephrology follow-up after hospitalization with acute kidney injury and temporary dialysis was associated with improved survival.