Renal function and cortical (Na(+)+K(+))-ATPase activity, abundance and distribution after ischaemia-reperfusion in rats

R, Leuvenink HGD, van der Heijden JW, Vogt L. Alkaline phosphatase treatment of acute kidney injury-an update

Through improved insights into the increasing incidence and detrimental effects of acute kidney injury (AKI), its clinical relevance has become more and more apparent. Although treatment strategies for AKI have also somewhat improved, an adequate remedy still does not exist. Finding one is complicated by a multifactorial pathophysiology and by heterogeneity in the patient population. Alkaline phosphatase (ALP) has been suggested as a therapy for sepsis-associated AKI because of its protective effects against lipopolysaccharide (LPS)-induced inflammation and kidney injury in animals. However, its effectiveness as an AKI treatment has not been demonstrated definitively. Because the anti-inflammatory properties of ALP are likely not reliant on a direct effect on LPS itself, we postulate that other pathways are much more important in explaining the renoprotective properties ascribed to ALP. The re-evaluation of which properties of the ALP enzyme are responsible for the benefit seen in the lab is an important step in determining where the true potential of ALP as a treatment strategy for AKI in the clinic lies. In this review we will discuss how ALP can prevent activation of harmful pro-inflammatory receptors, redirect cell-cell signalling and protect barrier tissues, which together form the basis for current knowledge of the role of ALP in the kidney. With this knowledge in mind and by analysing currently available clinical evidence, we propose directions for new research that can determine whether ALP as a treatment strategy for AKI has a future in the clinical field.

Increased Drop in Activity of Alkaline Phosphatase in Plasma from Patients with Endocarditis

(1) Infective endocarditis is a severe inflammatory disease associated with substantial mortality and morbidity. Alkaline phosphatase (AP) levels have been shown to change significantly during sepsis. Additionally, we previously found that a higher initial AP drop after cardiac surgery is associated with unfavorable outcomes. Therefore, the course of AP after surgery for endocarditis is of special interest. (2) A total of 314 patients with active isolated left-sided infective endocarditis at the Department of Cardiac Surgery (Medical University of Vienna, Vienna, Austria) between 2009 and 2018 were enrolled in this retrospective analysis. Blood samples were analyzed at different time points (baseline, postoperative days 1-7, postoperative days 14 and 30). Patients were categorized according to relative alkaline phosphatase drop (≥30% vs. <30%). (3) A higher rate of postoperative renal replacement therapy with or without prior renal replacement therapy (7.4 vs. 21.8%; p = 0.001 and 6.7 vs. 15.6%; p = 0.015, respectively) and extracorporeal membrane oxygenation (2.2 vs. 19.0%; p = 0.000) was observed after a higher initial alkaline phosphatase drop. Short-term (30-day mortality 3.0 vs. 10.6%; p = 0.010) and long-term mortality (p = 0.008) were significantly impaired after a higher initial alkaline phosphatase drop. (4) The higher initial alkaline phosphatase drop was accompanied by impaired short- and long-term outcomes after cardiac surgery for endocarditis. Future risk assessment scores for cardiac surgery should consider alkaline phosphatase.

Treprostinil reduces mitochondrial injury during rat renal ischemia-reperfusion injury

BACKGROUND

Renal ischemia-reperfusion injury (IRI) is a major factor contributing to acute kidney injury and it is associated with a high morbidity and mortality if untreated. Renal IRI depletes cellular and tissue adenosine triphosphate (ATP), which compromises mitochondrial function, further exacerbating renal tubular injury. Currently, no treatment for IRI is available. This study investigates the protective role of treprostinil in improving mitochondria biogenesis and recovery during rat renal IRI.

METHODS

Male Sprague Dawley rats were randomly assigned to groups: control, sham, IRI-placebo or IRI-treprostinil and subjected to 45 min of bilateral renal ischemia followed by 1-72 h reperfusion. Placebo or treprostinil (100 ng/kg/min) was administered subcutaneously via an osmotic minipump.

RESULTS

Treprostinil significantly reduced peak elevated serum creatinine (SCr) levels and accelerated normalization relative to IRI-placebo (p < 0.0001). Treatment with treprostinil also inhibited IRI-mediated renal apoptosis, mitochondrial oxidative injury (p < 0.05), and the release of cytochrome c (p < 0.01) vs. IRI-placebo. In addition, treprostinil preserved renal mitochondrial DNA copy number (p < 0.0001) and renal ATP levels (p < 0.05) to nearly those of sham-operated animals. Non-targeted semi-quantitative proteomics showed reduced levels of ATP synthase subunits in the IRI-placebo group which were restored to sham levels by treprostinil treatment (p < 0.05). Furthermore, treprostinil reduced renal IRI-induced upregulated Drp1 and pErk protein levels, and restored Sirt3 and Pgc-1α levels to baseline (p < 0.05).

CONCLUSIONS

Treprostinil reduces mitochondrial-mediated renal apoptosis, inhibits mitochondria fission, and promotes mitochondria fusion, thereby accelerating mitochondrial recovery and protecting renal proximal tubules from renal IRI. These results support the clinical investigation of treprostinil as a viable therapy to reduce renal IRI.

Protective Effect of Hydroalcoholic Extract of Stachys pilifera on Oxidant-Antioxidant Status in Renal Ischemia/Reperfusion Injuries in Male Rats

Background

Renal ischemia-reperfusion (I/R) has a pivotal role in the progression of acute renal failure. Reactive oxygen species are considered the major constituents involved in the biochemical and pathophysiological changes that were shown during kidney I/R. The purpose of this study was to examine the renoprotective effects of Stachys pilifera ethanolic extract on oxidant-antioxidant status in renal I/R-injuries in male rats. Material and methods. Twenty-one male Wistar rats were arbitrarily distributed into 3 groups: sham control (SC), I/R, and I/R + Stachys pilifera ethanolic extract (500 mg/kg). The artery and vein of the right kidney were completely blocked, and the right kidney was completely removed in all groups. Then, the left kidney artery was blocked with suture thread for 30 minutes in only I/R and I/R + SP extract groups. Kidney function indices, oxidative stress markers, and hematoxylin and eosin staining were investigated in the plasma and kidney tissues.

Results

It was shown that the urine Na and K, fractional excretion of Na and K, and protein carbonyl content markedly increased in the merely I/R group as compared to SC rats, while the administration of SP extract markedly reduced these indices (P < 0.05). Also, glomerular filtration rate and total thiol meaningfully reduced in the I/R rats in contrast to the SC group, while the treatment with SP extract markedly augmented these indices (P < 0.05). However, in agreement with renal function tests, SP extract had no significant effects on histopathological examinations.

Conclusion

It seems that SP extract employs renoprotective effects on renal damage induced by I/R, possibly by improving of oxidant-antioxidant status in favor of the antioxidant system.

Tissue alkaline phosphatase activity and expression in an experimental infant swine model of cardiopulmonary bypass with deep hypothermic circulatory arrest

Background

Infant cardiac surgery with cardiopulmonary bypass results in decreased circulating alkaline phosphatase that is associated with poor postoperative outcomes. Bovine intestinal alkaline phosphatase infusion represents a novel therapy for post-cardiac surgery organ injury. However, the effects of cardiopulmonary bypass and bovine-intestinal alkaline phosphatase infusion on tissue-level alkaline phosphatase activity/expression are unknown.

Methods

Infant pigs (n = 20) underwent cardiopulmonary bypass with deep hypothermic circulatory arrest followed by four hours of intensive care. Seven control animals underwent mechanical ventilation only. Cardiopulmonary bypass/deep hypothermic circulatory arrest animals were given escalating doses of bovine intestinal alkaline phosphatase infusion (0-25 U/kg/hr.; n = 5/dose). Kidney, liver, ileum, jejunum, colon, heart and lung were collected for measurement of tissue alkaline phosphatase activity and mRNA.

Results

Tissue alkaline phosphatase activity varied significantly across organs with the highest levels found in the kidney and small intestine. Cardiopulmonary bypass with deep hypothermic circulatory arrest resulted in decreased kidney alkaline phosphatase activity and increased lung alkaline phosphatase activity, with no significant changes in the other organs. Alkaline phosphatase mRNA expression was increased in both the lung and the ileum. The highest dose of bovine intestinal alkaline phosphatase resulted in increased kidney and liver tissue alkaline phosphatase activity.

Conclusions

Changes in alkaline phosphatase activity after cardiopulmonary bypass with deep hypothermic circulatory arrest and bovine intestinal alkaline phosphatase delivery are tissue specific. Kidneys, lung, and ileal alkaline phosphatase appear most affected by cardiopulmonary bypass with deep hypothermic circulatory arrest and further research is warranted to determine the mechanism and biologic importance of these changes.

Effect of moonseed vine (Triclisia gilletii Staner) on ethane-1,2-diol-induced urolithiasis and its renotoxicity in Wistar albino rats

Background

Moonseed vine (Triclisia gilletii Staner) in the family Menispermaceae is a robust creeper of up to 10 cm diameter, of the lowland dense rain forest. In Ondo State, located in the South Western part of Nigeria, the plant which is usually called Peshe is used for the management of renal-related ailments. The present study was undertaken to explore the efficacy of Triclisia gilletii, a folkloric therapy in the management of renal-related ailment.

Results

Phenols, steroids, saponins, and flavonoids are present in the TGME with a total antioxidant capacity of (30.36 ± 1.90 (mg GAE/g extract), LD50 greater than 5000 mg/kg b.w., and in vitro anti-nucleation activity (iC50 = 7.09 mg/mL). Calcium oxalate stone formation as a result of oxalate from ethane-1,2-diol was evident by hypocalcemia, and further electrolyte imbalance and decreased glomerular filtration rate. The enhanced oxidative milieu in hyperoxaluria was evident by increased MDA and PC and decreased enzymatic and non-enzymatic antioxidants as well as renal membrane enzymes activities. The renal histopathological study further emphasized oxalate-induced damage and the ameliorative potential of TGME.

Conclusion

The abnormal biochemical, redox electrolyte, membrane integrity, and histological alterations were attenuated by TGME which affirms its usage as nephroprotectant.

Alkaline Phosphatase Treatment of Acute Kidney Injury in an Infant Piglet Model of Cardiopulmonary Bypass with Deep Hypothermic Circulatory Arrest

Acute kidney injury (AKI) is associated with prolonged hospitalization and mortality following infant cardiac surgery, but therapeutic options are limited. Alkaline phosphatase (AP) infusion reduced AKI in phase 2 sepsis trials but has not been evaluated for cardiac surgery-induced AKI. We developed a porcine model of infant cardiopulmonary bypass (CPB) with deep hypothermic circulatory arrest (DHCA) to investigate post-CPB/DHCA AKI, measure serum/renal tissue AP activity with escalating doses of AP infusion, and provide preliminary assessment of AP infusion for prevention of AKI. Infant pigs underwent CPB with DHCA followed by survival for 4 h. Groups were treated with escalating doses of bovine intestinal AP (1, 5, or 25U/kg/hr). Anesthesia controls were mechanically ventilated for 7 h without CPB. CPB/DHCA animals demonstrated histologic and biomarker evidence of AKI as well as decreased serum and renal tissue AP compared to anesthesia controls. Only high dose AP infusion significantly increased serum or renal tissue AP activity. Preliminary efficacy evaluation demonstrated a trend towards decreased AKI in the high dose AP group. The results of this dose-finding study indicate that AP infusion at the dose of 25U/kg/hr corrects serum and tissue AP deficiency and may prevent AKI in this piglet model of infant CPB/DHCA.

Glutamine protection in an experimental model of acetaminophen nephrotoxicity

Acetaminophen (APAP) is a widely prescribed analgesic and antipyretic drug. In the present work, we studied the effects of glutamine (Gln) in an in vivo model of APAP-induced nephrotoxicity in male Wistar rats. Renal function, histological characteristics, and Na+,K+-ATPase cortical abundance and distribution were analyzed. The appearance of HSP70 and actin in urine was also evaluated. Myeloperoxidase (MPO) activity in cortical tissue was measured as an index of the inflammatory response. Gln administration 30 min before APAP protected from the renal functional and histological damage promoted by APAP. Rats that received the dual treatment Gln and APAP (Gln/APAP) showed the same level of Na+,K+-ATPase cortical induction as APAP-treated animals, but the enzyme maintained its normal basolateral localization. HSP70 abundance was increased up to the same level in the Gln, APAP, and Gln/APAP groups. Urinary HSP70 and actin were detected only in the APAP-treated animals, reinforcing the protection of renal tubular integrity afforded by the Gln pretreatment. Gln pretreatment also protected from the increment in MPO activity promoted by APAP. Our results support the idea that Gln pretreatment could be a therapeutic option to prevent APAP-induced renal injury.

Ischemia/reperfusion-associated tubular cells injury in renal transplantation: Can metabolomics inform about mechanisms and help identify new therapeutic targets?

Tubular cells are central targets of ischemia-reperfusion (I/R) injury in kidney transplantation. Inflammation and metabolic disturbances occurring within these cells are deleterious by themselves but also favor secondary events, such as activation of immune response. It is critical to have an in depth understanding of the mechanisms governing tubular cells response to I/R if one wants to define pertinent biomarkers or to elaborate targeted therapeutic interventions. As oxidative damage was shown to be central in the patho-physiological mechanisms, the impact of I/R on proximal tubular cells metabolism has been widely studied, contrary to its effects on expression and activity of membrane transporters of the proximal tubular cells. Yet, temporal modulation of transporters over ischemia and reperfusion periods appears to play a central role, not only in the induction of cells injury but also in graft function recovery. Metabolomics in cell models or diverse biofluids has the potential to provide large pictures of biochemical consequences of I/R. Metabolomic studies conducted in experimental models of I/R or in transplanted patients indeed retrieved metabolites belonging to the pathways known to be particularly affected. Interestingly, they also revealed that metabolic disturbances and transporters activities are in very close mutual interplay. As well as helping to select diagnostic biomarkers, such analyses could also contribute to identify new pharmacological targets and to set up innovative nephroprotective strategies for the future. Even if various therapeutic approaches have been evaluated for a long time to prevent or treat I/R injuries, metabolomics has helped identifying new ones, those related to membrane transporters seeming to be of particular interest. However, considering the very complex and multifactorial effects of I/R in the context of kidney transplantation, all tracks must be followed if one wants to prevent or limit its deleterious consequences.

Biodistribution and translational pharmacokinetic modeling of a human recombinant alkaline phosphatase

Clinical trials showed renal protective effects of bovine intestinal alkaline phosphatase (AP) in patients with sepsis-associated acute kidney injury (AKI). Subsequently, a human recombinant chimeric AP (recAP) was developed as a pharmaceutically acceptable alternative. Here, we investigated the biodistribution and pharmacokinetics (PK) of recAP and developed a translational population PK model. Biodistribution was studied during LPS-induced AKI in rats. Iodine-125-labeled recAP was primarily taken up by liver, spleen, adrenals, heart, lungs and kidneys followed by the gastro-intestinal tract and thyroid. Tissue distribution was not critically affected by endotoxemia. PK parameters were determined in rats and minipigs during IV bolus injections of recAP, administered once, or once daily during seven consecutive days. Plasma concentrations of recAP increased with increasing dose and disappeared in a biphasic manner. Exposure to recAP, estimated by AUC and Cmax, was similar on days 1 and 7. Subsequently, population approach nonlinear mixed effects modeling was performed with recAP rat and minipig and biAP phase I PK data. Concentration versus time data was accurately described in all species by a two-compartmental model with allometric scaling based on body weight. This model provides a solid foundation for determining the optimal dose and duration of first-in-man recAP studies.

Alkaline phosphatase: a possible treatment for sepsis-associated acute kidney injury in critically ill patients

Acute kidney injury (AKI) is a common disease in the intensive care unit and accounts for high morbidity and mortality. Sepsis, the predominant cause of AKI in this setting, involves a complex pathogenesis in which renal inflammation and hypoxia are believed to play an important role. A new therapy should be aimed at targeting both these processes, and the enzyme alkaline phosphatase, with its dual mode of action, might be a promising candidate. First, alkaline phosphatase is able to reduce inflammation through dephosphorylation and thereby detoxification of endotoxin (lipopolysaccharide), which is an important mediator of sepsis. Second, adenosine triphosphate, released during cellular stress caused by inflammation and hypoxia, has detrimental effects but can be converted by alkaline phosphatase into adenosine with anti-inflammatory and tissue-protective effects. These postulated beneficial effects of alkaline phosphatase have been confirmed in animal experiments and two phase 2a clinical trials showing that kidney function improved in critically ill patients with sepsis-associated AKI. Because renal inflammation and hypoxia also are observed commonly in AKI induced by other causes, it would be of interest to investigate the therapeutic effect of alkaline phosphatase in these nephropathies as well.

Oat5 and NaDC1 protein abundance in kidney and urine after renal ischemic reperfusion injury

The aim of this study was to evaluate the abundance of the organic anion transporter 5 (Oat5) and the sodium-dicarboxylate cotransporter 1 (NaDC1) in kidney and urine after renal ischemic reperfusion injury. Renal injury was induced in male Wistar rats by occlusion of both renal pedicles for 0 (Group Sham), 5 (Group I5R60), or 60 (Group I60R60) min. The studies were performed after 60 min of reperfusion. The expression of Oat5 and NaDC1 was evaluated by IHC and Western blotting. Oat5 and NaDC1 abundance and alkaline phosphatase activity (AP) were assayed in urine. A decreased expression in renal homogenates and apical membranes and an increase in urinary excretion of Oat5 and NaDC1 were observed in I60R60 rats, as well as alterations of other widely used parameters for renal dysfunction and injury (plasma creatinine, urinary AP activity, kidney weight, histological lesions). In contrast, in the I5R60 group, only an increase in urinary excretion of Oat5 and mild histopathological damage was detected. This is the first study on Oat5 and NaDC1 detection in urine. These results suggest that urinary excretion of Oat5 might be an early indicator of renal dysfunction, which is useful for detection of even minor alterations in renal structural and functional integrity.

Elimination of organic anions in response to an early stage of renal ischemia-reperfusion in the rat: role of basolateral plasma membrane transporters and cortical renal blood flow

BACKGROUND/AIMS

The knowledge of molecular mechanisms determining drug pharmacokinetics in pathological states is relevant for the development of new therapeutic approaches. This study was undertaken to evaluate the cortical renal blood flow (cRBF) and the renal protein expression of the organic anion transporters (OAT1 and OAT3) in association with the elimination of organic anions in an early stage of renal ischemia-reperfusion.

METHODS

Ischemic acute renal failure (ARF) was induced in adult male Wistar rats by occlusion of both renal pedicles during 60 min, followed by 60 min of reperfusion (ARF group). Pair-fed sham-operated rats served as controls. The renal protein expression of OAT1 and OAT3 was evaluated by immunohistochemistry techniques and by Western blotting in renal cortex homogenates and in basolateral plasma membranes. A pharmacokinetic study of p-aminohippurate (PAH, a prototypical organic anion) was performed. cRBF was determined using fluorescent microspheres.

RESULTS

ARF rats displayed a significant decrease in systemic clearance and in renal excretion of PAH. OAT1 and OAT3 protein abundance showed a statistically significant reduction both in homogenates and in basolateral plasma membranes from ARF rats. Immunohistochemical studies confirmed the changes in the cortical renal expression of these transporters. ARF animals also showed a decrease in cRBF.

CONCLUSIONS

The decrease in PAH elimination observed in an early stage of renal ischemia-reperfusion in male Wistar rats might be explained by the sum of the lower OAT1 and OAT3 expression in renal basolateral plasma membranes plus the decrease in cRBF. These findings might have significant implications in the development of novel pharmacological strategies to be applied in the initial stages of ischemic ARF.

Urinary concentrating mechanism and Aquaporin-2 abundance in rats chronically treated with aluminum lactate

The aim of this work was to study the effects of chronic administration of aluminum (Al) on the urinary concentrating and diluting mechanisms in the distal tubules and collecting ducts. Male Wistar rats were chronically treated with aluminum lactate for 12 weeks (0.575 mg Al/100g of body weight, i.p., three times per week). After 12 weeks, renal function of control and Al-treated rats was evaluated by clearance techniques. To study urinary concentrating mechanisms, renal function was also measured in control and Al-treated rats deprived of water, after the administration of desmopressin (vasopressin agonist) and after the infusion of hypertonic saline at increasing infusion rates. Sodium and water balance were impaired. We found decreased urinary concentrating ability in situations in which endogenous (thirst or infusion of hypertonic saline) or exogenous plasma antidiuretic hormone was increased. Solute-free water formation, measured during the infusion of hypotonic saline showed normal transport in the thick ascending limb. Aquaporin-2 (AQP2) expression was measured by Western blot to evaluate water permeability in collecting ducts. We found that Al produced downregulation of AQP2 in plasma membranes and intracellular vesicles, that could account for the impaired water handling. Administration of desmopressin increased AQP2 in plasma membranes, suggesting that Al did not impair trafficking of this protein, but could interfere with AQP2 synthesis.

Evolution of renal function and Na+, K +-ATPase expression during ischaemia-reperfusion injury in rat kidney

The aim of the present work was to study the effects of an unilateral ischaemic-reperfusion injury on Na+, K+-ATPase activity, alpha1 and beta1 subunits protein and mRNA abundance and ATP content in cortical and medullary tissues from postischaemic and contralateral kidneys. Right renal artery was clamped for 40 min followed by 24 and 48 h of reperfusion. Postischaemic and contralateral renal function was studied cannulating the ureter of each kidney. Postischaemic kidneys after 24 (IR24) and 48 (IR48) hours of reperfusion presented a significant dysfunction. Na+, K+-ATPase alpha1 subunit abundance increased in IR24 and IR48 cortical tissue and beta1 subunit decreased in IR48. In IR24 medullary tissue, alpha1 abundance increased and returned to control values in IR48 while beta1 abundance was decreased in both periods. Forty minutes of ischaemia without reperfusion (I40) promoted an increment in alpha1 mRNA in cortex and medulla that normalised after 24 h of reperfusion. beta1 mRNA was decreased in IR24 medullas. No changes were observed in contralateral kidneys. This work provides evidences that after an ischaemic insult alpha1 and beta1 protein subunit abundance and mRNA levels are independently regulated. After ischaemic-reperfusion injury, cortical and medullary tissue showed a different pattern of response. Although ATP and Na+, K+-ATPase activity returned to control values, postischemic kidney showed an abnormal function after 48 h of reflow.

Indomethacin induces free radical-mediated changes in renal brush border membranes

Nonsteroidal anti-inflammatory drugs (NSAIDs) are used extensively in clinical medicine. One disadvantage of their use, however, is the occurrence of adverse effects in the kidneys. The side effects produced in this organ have been classically attributed to the inhibitory effect of these drugs on the activity of cyclooxygenase, a key enzyme in prostaglandin synthesis. Our earlier work with indomethacin, a commonly used NSAID, has shown that oxidative stress and mitochondrial dysfunction occur in the kidney in response to the drug. In view of this, this study looked into the effect of indomethacin on brush border membranes (BBM) from the kidney, as these biomembranes are prime targets of oxygen free radicals. Rats, fasted overnight, were dosed with indomethacin (20 mg/kg) by gavage and sacrificed 24 h later. BBM were isolated from the kidneys by polyethylene glycol precipitation. It was found that there was an increase in levels of products of peroxidation and a fall in the level of alpha-tocopherol in the BBM from indomethacin-dosed rats. These BBM also exhibited impaired glucose transport. The lipid composition of the membranes was also found to be altered. Alterations in lipids were associated with up-regulation of phospholipase A2. Pretreatment with L-arginine, a nitric oxide donor, protected against these effects of indomethacin. Thus, this study suggests that indomethacin induces impairment in structure and function of BBM in the kidney, with these effects possibly mediated by free radicals and activation of phospholipases. We postulate that such alterations may be important in the pathogenesis of NSAID-induced nephropathy.

Sex differences in the alterations of Na(+), K(+)-ATPase following ischaemia-reperfusion injury in the rat kidney

Postischaemic acute renal failure (ARF) is influenced by sex. Na(+), K(+)-ATPase (NKA) plays a crucial role in the pathogenesis of postischaemic ARF. We tested the impact of sex on mRNA, protein expression, cellular distribution and enzyme activity of NKA following renal ischaemia-reperfusion (I-R) injury. The left renal pedicle of uninephrectomized female (F) and male (M) Wistar rats was clamped for 55 min followed by 2 h (T2) and 16 h (T16) of reperfusion. Uninephrectomized, sham-operated F and M rats served as controls (n= 6 per group). Blood urea nitrogen, serum creatinine and renal histology were evaluated to detect the severity of postischaemic ARF. mRNA expression of NKA alpha1 and beta1 subunits were detected by RT-PCR. The effect of I-R on cellular distribution was compared by Triton X-100 extraction. Cellular proteins were divided into Triton-insoluble and Triton-soluble fractions and assessed by Western blot. NKA enzyme activity was also determined. After the ischaemic insult blood urea nitrogen and serum creatinine were higher and renal histology showed more rapid progression in M versus F (P < 0.05). mRNA expression of the NKA alpha1 subunit decreased in I-R groups versus controls, but was higher in F versus M both in control and I-R groups (P < 0.05). However, protein levels of the NKA alpha1 subunit in total tissue homogenate did not differ in controls, but were higher in F versus M in I-R groups (P < 0.05). Triton X-100 extractability was lower in F versus M at T16 (P < 0.05). NKA enzyme activity was the same in controls, but was higher in F versus M in I-R groups (T2: 14.9 +/- 2.3 versus 9.15 +/- 2.21 U) (T16: 11.7 +/- 4.1 versus 5.65 +/- 2.3 U; P < 0.05). mRNA and protein expression of the NKA beta1 subunit did not differ between F and M in any of the protocol. We concluded that NKA is more protected from the detrimental effects of postischaemic injury in females. Higher mRNA and protein expression of the NKA alpha1 subunit and higher enzyme activity might be additional contributing factors to the improved postischaemic renal function of female rats.