Ouabain Protects Nephrogenesis in Rats Experiencing Intrauterine Growth Restriction and Partially Restores Renal Function in Adulthood

Intrauterine growth restriction (IUGR) is, in general, accompanied by a reduction of the nephron number, which increases the risk of hypertension and renal dysfunction. Studies have revealed that ouabain can partially restore the number of nephrons during IUGR. However, there is limited information regarding the melioration of nephric structure and function. We used maternal malnutrition to induce an IUGR model in rats. Subsequently, we used a mini-pump to administer ouabain to IUGR rats during pregnancy. Male offspring were divided randomly into two groups. One group was fed a normal diet, whereas the other was fed an isocaloric 8% high-salt diet. Maternal malnutrition led to a reduction in the birth weight and number of nephrons in offspring. At the end of a 40-week follow-up period, offspring from the IUGR group had high blood pressure and abnormal excretion of urinary protein; these parameters were exacerbated in offspring fed a high-salt diet. However, ouabain administration during pregnancy could partially restore the number of nephrons in IUGR offspring, normalize blood pressure, and reduce urinary protein excretion, even when challenged with a high-salt diet. Pathology findings revealed that IUGR, particularly following feeding of a high-salt diet, damaged the ultrastructure of glomeruli, but these harmful effects were ameliorated in offspring treated with ouabain. Collectively, our data suggest that ouabain could rescue nephrogenesis in IUGR newborns and protect (at least in part) the structure and function of the kidney during adulthood even when encountering unfavorable environmental challenges in subsequent life.

Changing Protein Permeability with Nephron Loss: Evidence for a Human Remnant Nephron Effect

BACKGROUND

If loss of functioning nephrons predisposes to glomerular barotrauma (a "remnant nephron" effect), then glomerular permeability should increase as glomerular filtration rate (GFR) falls, as is observed in animal models of nephron loss.

METHODS

Changes in net renal protein permeability, defined as proteinuria or albuminuria per mL/min of GFR, were measured in the setting of nephron loss due to kidney donation (Assessing Long Term Outcomes in Living Kidney Donors cohort) or progressive chronic kidney disease (CKD; Modification of Diet in Renal Disease [MDRD], African American Study of Kidney Disease [AASK], and Chronic Renal insufficiency Cohort [CRIC] studies).

RESULTS

Following kidney donation, renal albumin permeability increased by 31% from predonation levels (p < 0.001). With progression of CKD, a 50% loss of residual GFR was accompanied by increases in proteinuria per mL/min GFR of 1.8-, 2.1-, and 1.6-fold in the MDRD, AASK, and CRIC cohorts, respectively (p < 0.001 for all), independent of changes in systolic blood pressure and ACEi/ARB use. A 70% reduction in GFR was associated with permeability increases of 3.1-, 4.4-, and 2.6-fold in the same cohorts. Among MDRD participants with progression of nonglomerular primary disease, the 75th percentile of final permeability was 141 mg/24 h proteinuria per mL/min GFR. This degree of permeability would have resulted in nephrotic range proteinuria had it been present at the baseline mean GFR of 40 mL/min, implying the development of de novo glomerular pathology as GFR fell. Increasing permeability also accompanied CKD progression in participants with nephrotic syndrome at baseline. Consequently, these participants had little improvement in 24 h proteinuria or serum albumin, despite substantial loss of functioning nephron mass across which the protein leak occurred. In the absence of a fall in GFR, there was no increase in permeability in any cohort.

CONCLUSION

Nephron loss is accompanied by an increase in renal protein permeability, even in the absence of a primary glomerular disease. This is consistent with a remnant nephron effect in human CKD.

Phase III Trial of Intravenous Mannitol Versus Placebo During Nephron-sparing Surgery: Post Hoc Analysis of 3-yr Outcomes

Our recently reported phase III trial demonstrated that patients undergoing nephron-sparing surgery (NSS) with an estimated glomerular filtration rate (eGFR) of ≥45 ml/min/1.73 m² who received mannitol had no improvement in renal function at 6 mo compared with those who received placebo. Some authors have suggested that benefit is restricted to subgroups, such as those with comorbidities. We assessed whether preoperative eGFR, or other patient and surgical factors modified the effect of mannitol on postoperative outcomes at 6 mo and with extended follow-up. We also assessed whether mannitol was associated with differences in long-term GFR years after surgery. No significant difference between the mannitol or placebo groups (mean eGFR difference: 1.4; 95% confidence interval: -2.6, 5.3; p = 0.5) was found in the 134 patients with known eGFR at 3 yr after NSS. At both 6 mo and 3 yr, the effect of mannitol was not significantly modified by patient or surgical factors including preoperative eGFR. In summary, we validated our original trial conclusions by finding that intraoperative use of mannitol does not improve either short- or long-term renal function in patients undergoing NSS. Specifically, there is no evidence that comorbidities, including lower preoperative eGFR, modify the effect of mannitol. PATIENT SUMMARY: Use of mannitol at the time of partial nephrectomy does not improve either short- or long-term renal function even in patients with comorbidities, including lower preoperative renal function. The routine use of intraoperative mannitol should be discontinued.

Regenerative potential of induced pluripotent stem cells derived from patients undergoing haemodialysis in kidney regeneration

Kidney regeneration from pluripotent stem cells is receiving a lot of attention because limited treatments are currently available for chronic kidney disease (CKD). It has been shown that uremic state in CKD is toxic to somatic stem/progenitor cells, such as endothelial progenitor and mesenchymal stem cells, affecting their differentiation and angiogenic potential. Recent studies reported that specific abnormalities caused by the non-inherited disease are often retained in induced pluripotent stem cell (iPSC)-derived products obtained from patients. Thus, it is indispensable to first assess whether iPSCs derived from patients with CKD due to non-inherited disease (CKD-iPSCs) have the ability to generate kidneys. In this study, we generated iPSCs from patients undergoing haemodialysis due to diabetes nephropathy and glomerulonephritis (HD-iPSCs) as representatives of CKD-iPSCs or from healthy controls (HC-iPSCs). HD-iPSCs differentiated into nephron progenitor cells (NPCs) with similar efficiency to HC-iPSCs. Additionally, HD-iPSC-derived NPCs expressed comparable levels of NPC markers and differentiated into vascularised glomeruli upon transplantation into mice, as HC-iPSC-derived NPCs. Our results indicate the potential of HD-iPSCs as a feasible cell source for kidney regeneration. This is the first study paving the way for CKD patient-stem cell-derived kidney regeneration, emphasising the potential of CKD-iPSCs.

Salt, water and nephron: Mechanisms of action and link to hypertension and chronic kidney disease

Our knowledge on sodium and water homeostasis and regulation continues to evolve. A considerable amount of new information in this area has emerged in recent years. This review summarizes existing and new literature and discusses complex multi-organ effects of high-salt and low-water intake and role of arginine vasopressin in this process, as well as the potential clinical significance of non-osmotic sodium storage pool and rhythmicity of urine sodium excretion. It has become clear that sodium and water dysregulation can exert profound effects on kidney and vascular health, far greater than previously recognized. Maladaptation to a combined high-salt and low-water intake can be linked to the growing epidemic of hypertension and chronic kidney disease.

Single-nephron proteomes connect morphology and function in proteinuric kidney disease

In diseases of many parenchymatous organs, heterogeneous deterioration of individual functional units determines the clinical prognosis. However, the molecular characterization at the level of such individual subunits remains a technological challenge that needs to be addressed in order to better understand pathological mechanisms. Proteinuric glomerular kidney diseases are frequent and assorted diseases affecting a fraction of glomeruli and their draining tubules to variable extents, and for which no specific treatment exists. Here, we developed and applied a mass spectrometry-based methodology to investigate heterogeneity of proteomes from individually isolated nephron segments from mice with proteinuric kidney disease. In single glomeruli from two different mouse models of sclerotic glomerular disease, we identified a coherent protein expression module consisting of extracellular matrix protein deposition (reflecting glomerular sclerosis), glomerular albumin (reflecting proteinuria) and LAMP1, a lysosomal protein. This module was associated with a loss of podocyte marker proteins while genetic ablation of LAMP1-correlated lysosomal proteases could ameliorate glomerular damage in vivo. Furthermore, proteomic analyses of individual glomeruli from patients with genetic sclerotic and non-sclerotic proteinuric diseases revealed increased abundance of lysosomal proteins, in combination with a decreased abundance of mutated gene products. Thus, altered protein homeostasis (proteostasis) is a conserved key mechanism in proteinuric kidney diseases. Moreover, our technology can capture intra-individual variability in diseases of the kidney and other tissues at a sub-biopsy scale.

SGLT2 inhibition in a kidney with reduced nephron number: modeling and analysis of solute transport and metabolism

Sodium-glucose cotransporter 2 (SGLT2) inhibitors enhance urinary glucose, Na+ and fluid excretion, and lower hyperglycemia in diabetes by targeting Na+ and glucose reabsorption along the proximal convoluted tubule. A goal of this study was to predict the effects of SGLT2 inhibitors in diabetic and nondiabetic patients with chronic kidney disease. To that end, we employed computational rat kidney models to explore how SGLT2 inhibition affects renal solute transport and metabolism when nephron populations are normal or reduced. Model simulations suggested that in a nondiabetic rat, acute and chronic SGLT2 inhibition induces glucosuria, diuresis, natriuresis, and kaliuresis. Those effects were stronger with chronic SGLT2 inhibition (due to SGLT1 downregulation) and tempered by nephron loss. In a diabetic rat with normal nephron number, acute SGLT2 inhibition similarly elevated urine fluid, Na+, and K+ excretion, whereas the urinary excretory effects of chronic SGLT2 inhibition were attenuated in proportion to its plasma glucose level lowering effect. Nephron loss in a diabetic kidney was predicted to lower the glucosuric and blood glucose-reducing effect of chronic SGLT2 inhibition, but due to the high luminal glucose delivery in the remaining hyperfiltering nephrons, nephron loss enhanced proximal tubular paracellular Na+ secretion, thereby augmenting the natriuretic, diuretic, and kaliuretic effects. A proposed shift in oxygen-consuming active transport to the outer medulla, which may simulate systemic hypoxia and enhance erythropoiesis, was also preserved with nephron loss. These effects may contribute to the protective effects of SGLT2 inhibitors on blood pressure and heart failure observed in diabetic patients with chronic kidney diseases.

Kidney Function in Patients With Different Variants of Beta-Thalassemia

INTRODUCTION

Renal involvement is a rare complication of β-thalassemia. Both tubular and glomerular dysfunction might occur in these patients. The aim of this study was to evaluate and compare kidney function in the major, intermedia, and minor variants of β-thalassemia.

MATERIALS AND METHODS

Renal tubular and glomerular function of 72 patients with β-thalassemia (25 major, 23 intermedia, and 24 minor) were evaluated. Patients older than 40 years and those with chronic kidney disease, diabetes mellitus, congestive heart failure, associated infections, congenital anomalies of the kidney and urinary tract were excluded. Blood and urine samples were collected electrolytes and markers of kidney function.

RESULTS

Mean age at the time of study was significantly higher in the minor group. The majority of patients with thalassemia major were males. Hematuria and pyuria occurred in 4% to 8% of the patients. Serum level of all variables were within normal limits, with no significant difference between the three groups. Glomerular filtration rate was nonsignificantly higher in the major and intermedia groups, compared to the minor variant. A significantly lower urine phosphorus and uric acid excretion was noted with the minor variant. Urine phosphorus and uric acid excretion increased more frequently in the major and intermedia groups.

CONCLUSIONS

Tubular and glomerular functions appear to be well preserved in all variants of β-thalassemia.

Association of Increasing GFR with Change in Albuminuria in the General Population

BACKGROUND AND OBJECTIVES

Hyperfiltration at the single-nephron level has been proposed as an early stage of kidney dysfunction of different origins. Evidence supporting this hypothesis in humans is lacking, because there is no method of measuring single-nephron GFR in humans. However, increased whole-kidney GFR in the same individual implies an increased single-nephron GFR, because the number of nephrons does not increase with age. We hypothesized that an increase in GFR would be associated with an increased albumin-to-creatinine ratio in a cohort of the general population.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We measured GFR by iohexol clearance at baseline in 2007-2009 and follow-up after 5.6 years in a representative sample of 1246 persons (aged 50-62 years) who were nondiabetic from the general population of Tromso, northern Norway. Participants were without cardiovascular disease, kidney disease, or diabetes at baseline. We investigated the association between change in GFR and change in albumin-to-creatinine ratio. Increased GFR was defined as a positive change in GFR (change in GFR>0 ml/min) from baseline to follow-up. An albumin-to-creatinine ratio >30 mg/g was classified as albuminuria.

RESULTS

Change in GFR was positively associated with a change in albumin-to-creatinine ratio in the entire cohort in the multiple linear regression. The albumin-to-creatinine ratiofollow-up-to-albumin-to-creatinine ratiobaseline ratio increased by 8.0% (95% confidence interval, 1.4 to 15.0) per SD increase in change in GFR. When participants with increased GFR (n=343) were compared with those with a reduced GFR (n=903), the ratio increased by 16.3% (95% confidence interval, 1.1 to 33.7). The multivariable adjusted odds ratio for incident albuminuria (n=14) was 4.98 (95% confidence interval, 1.49 to 16.13) for those with an increased GFR (yes/no).

CONCLUSIONS

Increasing GFR is associated with an increase in albumin-to-creatinine ratio and incident albuminuria in the general nondiabetic population. These findings support single-nephron hyperfiltration as a risk factor for albuminuria in the general population.

Integrated control of Na transport along the nephron

The kidney filters vast quantities of Na at the glomerulus but excretes a very small fraction of this Na in the final urine. Although almost every nephron segment participates in the reabsorption of Na in the normal kidney, the proximal segments (from the glomerulus to the macula densa) and the distal segments (past the macula densa) play different roles. The proximal tubule and the thick ascending limb of the loop of Henle interact with the filtration apparatus to deliver Na to the distal nephron at a rather constant rate. This involves regulation of both filtration and reabsorption through the processes of glomerulotubular balance and tubuloglomerular feedback. The more distal segments, including the distal convoluted tubule (DCT), connecting tubule, and collecting duct, regulate Na reabsorption to match the excretion with dietary intake. The relative amounts of Na reabsorbed in the DCT, which mainly reabsorbs NaCl, and by more downstream segments that exchange Na for K are variable, allowing the simultaneous regulation of both Na and K excretion.

Deciphering physiological role of the mechanosensitive TRPV4 channel in the distal nephron

Long-standing experimental evidence suggests that epithelial cells in the renal tubule are able to sense osmotic and pressure gradients caused by alterations in ultrafiltrate flow by elevating intracellular Ca(2+) concentration. These responses are viewed as critical regulators of a variety of processes ranging from transport of water and solutes to cellular growth and differentiation. A loss in the ability to sense mechanical stimuli has been implicated in numerous pathologies associated with systemic imbalance of electrolytes and to the development of polycystic kidney disease. The molecular mechanisms conferring mechanosensitive properties to epithelial tubular cells involve activation of transient receptor potential (TRP) channels, such as TRPV4, allowing direct Ca(2+) influx to increase intracellular Ca(2+) concentration. In this review, we critically analyze the current evidence about signaling determinants of TRPV4 activation by luminal flow in the distal nephron and discuss how dysfunction of this mechanism contributes to the progression of polycystic kidney disease. We also review the physiological relevance of TRPV4-based mechanosensitivity in controlling flow-dependent K(+) secretion in the distal renal tubule.

The impact of maternal cigarette smoke exposure in a rodent model on renal development in the offspring

This study aimed to investigate whether maternal cigarette smoke exposure can disrupt fetal kidney development by changing the expression of growth and transcription factors essential for renal development, and thereafter predispose the offspring to chronic kidney disease later in life. Female Balb/c mice (6 weeks) were exposed either to cigarette smoke or air under identical conditions, 6 weeks prior to mating, during gestation and during lactation. Male offspring were sacrificed at three time points, postnatal day (P)1, P20 (weaning age), and 13 weeks (mature age). Blood, urine, and kidneys were collected for analysis. At P1, the developmental genes fibroblast growth factor 2, glial cell-line derived neurotrophic factor and paired box 2 were upregulated at mRNA and protein levels; whilst fibroblast growth factor (FGF) 7 and FGF10 were downregulated. At P20, mRNA expression of FGF2, FGF10 and Wingless-type 4 was upregulated by maternal smoke exposure. These changes were normalised in adulthood. Nephron development was delayed, with fewer nephron numbers from P1 persisted to adulthood; while glomerular volume was increased at P20 but reduced in adulthood. Pro-inflammatory marker monocyte chemoatractant protein 1 (MCP1) was increased in the kidney by maternal smoke exposure. These changes were accompanied by an increased albumin/creatinine ratio in adulthood, suggesting reduced renal dysfunction. In conclusion maternal cigarette smoke exposure prior to and during pregnancy, as well as lactation leads to significant renal underdevelopment and functional abnormalities in adulthood. This study confirms the hypothesis that maternal smoking predisposes offspring to chronic kidney disorders.

Acute kidney injury urinary biomarker time-courses

Factors which modify the excretion profiles of acute kidney injury biomarkers are difficult to measure. To facilitate biomarker choice and interpretation we modelled key modifying factors: extent of hyperfiltration or reduced glomerular filtration rate, structural damage, and reduced nephron number. The time-courses of pre-formed, induced (upregulated), and filtered biomarker concentrations were modelled in single nephrons, then combined to construct three multiple-nephron models: a healthy kidney with normal nephron number, a non-diabetic hyperfiltering kidney with reduced nephron number but maintained total glomerular filtration rate, and a chronic kidney disease kidney with reduced nephron number and reduced glomerular filtration rate. Time-courses for each model were derived for acute kidney injury scenarios of structural damage and/or reduced nephron number. The model predicted that pre-formed biomarkers would respond quickest to injury with a brief period of elevation, which would be easily missed in clinical scenarios. Induced biomarker time-courses would be influenced by biomarker-specific physiology and the balance between insult severity (which increased single nephron excretion), the number of remaining nephrons (reduced total excretion), and the extent of glomerular filtration rate reduction (increased concentration). Filtered biomarkers have the longest time-course because plasma levels increased following glomerular filtration rate decrease. Peak concentration and profile depended on the extent of damage to the reabsorption mechanism and recovery rate. Rapid recovery may be detected through a rapid reduction in urinary concentration. For all biomarkers, impaired hyperfiltration substantially increased concentration, especially with chronic kidney disease. For clinical validation of these model-derived predictions the clinical biomarker of choice will depend on timing in relation to renal insult and interpretation will require the pre-insult nephron number (renal mass) and detection of hyperfiltration.

Does a nephron deficit exacerbate the renal and cardiovascular effects of obesity?

It has been hypothesized that a reduced nephron endowment exacerbates the hypertensive and renal effects of obesity. We therefore examined the impact of diet-induced obesity on renal structure and function, and arterial pressure in a genetic model of reduced nephron endowment, the GDNF Heterozygous (HET) mouse. 6wk-old male GDNF WT and HET mice were placed on control or high fat (HFF) diet for 20 weeks. 24 hr arterial pressure, heart rate and activity (radiotelemetry), creatinine clearance and albumin excretion were measured, and kidneys collected (histopathology, collagen content). Bodyweights of HFF WT (50.6±1.2 g) and HET (48.8±1.4 g) mice were ∼14 g greater than control mice (37.3±1.3 g, 36.4±1.1 g respectively; Pdiet<0.001). Obesity led to significantly greater 24 hr MAP (Pdiet<0.001), heart rate (Pdiet<0.01) and lower locomotor activity (Pdiet<0.01) in HET and WT mice. Whilst there was no significant impact of genotype on 24 hr MAP response to obesity, night-time MAP of obese HET mice was significantly greater than obese WT mice (122.3±1.6 vs 116.9±1.3 mmHg; P<0.05). 24 hr creatinine clearance was 50%, and albumin excretion 180% greater in obese WT and HET mice compared to controls (Pdiet<0.05) but this response did not differ between genotypes. Obesity induced glomerulomegaly, glomerulosclerosis, tubulointerstitial expansion and increased collagen accumulation (total, collagen I, V and IV; Pdiet<0.001). Obese GDNF HET mice had exacerbated total renal collagen (P<0.01), and greater levels of the collagen I subtype compared to kidneys of obese WT mice. In summary, obese nephron-deficient GDNF HET mice were able to maintain the high creatinine clearances of obese WT mice but at the expense of higher MAP and greater renal fibrosis. Whilst modest, our findings support the hypothesis that a reduced nephron endowment increases the susceptibility to obesity-induced kidney disease and hypertension.

Genetic low nephron number hypertension is associated with altered expression of osteopontin and CD44 during nephrogenesis

AIMS

The study set out to investigate whether the osteopontin (OPN)-CD44-integrin-receptor-system is differently regulated during nephrogenesis in inborn nephron deficit, a major determinant of human primary hypertension and cardiovascular disease in adult life.

METHODS

We compared a genetic rat model with an inherited nephron deficit, the Munich-Wistar-Froemter rat (MWF), to normotensive Wistar rats during nephrogenesis at day 19 of fetal development (E19) and at postpartal day 7 (D7).

RESULTS

Renal OPN mRNA (-75%, P<0.05) and protein expression (-38%, P<0.05) were strongly decreased at E19 in MWF compared to Wistar. Renal mRNA-expression of CD44 was increased at E19 in MWF (+271%, P<0.05). At D7, renal OPN protein expression was increased (+115%, P<0.05) and renal mRNA-expression of CD44 remained elevated compared to Wistar control (+127%, P<0.05).

CONCLUSIONS

Altered fetal expression of the OPN-CD44-integrin-receptor-system in the MWF model points to a possible role in low nephron number hypertension and cardiovascular disease.

[Cellular factors of ischemia/reperfusion injury pathogenesis in the renal transplantation]

A review of literature reveales the current conception of Russian and foreign authors on the cellular and humoral pathogenetic mechanisms of ischemic and reperfusion injury of kidney transplant.

Uropathogenic Escherichia coli P and Type 1 fimbriae act in synergy in a living host to facilitate renal colonization leading to nephron obstruction

The progression of a natural bacterial infection is a dynamic process influenced by the physiological characteristics of the target organ. Recent developments in live animal imaging allow for the study of the dynamic microbe-host interplay in real-time as the infection progresses within an organ of a live host. Here we used multiphoton microscopy-based live animal imaging, combined with advanced surgical procedures, to investigate the role of uropathogenic Escherichia coli (UPEC) attachment organelles P and Type 1 fimbriae in renal bacterial infection. A GFP⁺ expressing variant of UPEC strain CFT073 and genetically well-defined isogenic mutants were microinfused into rat glomerulus or proximal tubules. Within 2 h bacteria colonized along the flat squamous epithelium of the Bowman's capsule despite being exposed to the primary filtrate. When facing the challenge of the filtrate flow in the proximal tubule, the P and Type 1 fimbriae appeared to act in synergy to promote colonization. P fimbriae enhanced early colonization of the tubular epithelium, while Type 1 fimbriae mediated colonization of the center of the tubule via a mechanism believed to involve inter-bacterial binding and biofilm formation. The heterogeneous bacterial community within the tubule subsequently affected renal filtration leading to total obstruction of the nephron within 8 h. Our results reveal the importance of physiological factors such as filtration in determining bacterial colonization patterns, and demonstrate that the spatial resolution of an infectious niche can be as small as the center, or periphery, of a tubule lumen. Furthermore, our data show how secondary physiological injuries such as obstruction contribute to the full pathophysiology of pyelonephritis.

When bacteria such as uropathogenic Escherichia coli (UPEC) infect a living kidney, they face numerous physiological challenges such as the flow of urine. Bacteria need to attach themselves to the epithelial linings of the kidney to withstand this flow. In this work we use a live animal imaging model to study how UPEC colonize a living kidney despite the physiological challenges they face. We show that P and Type 1 fimbriae, two of the most well described UPEC adhesion factors, work together to promote successful bacterial colonization. P fimbriae mediate binding between the bacteria and the epithelial cells lining the tubules, while Type 1 appears to play a role in inter-bacterial binding and biofilm formation in the center parts of the lumen. The heterogeneous bacterial community which filled the tubule was subsequently shown to effect nephron filtration and resulted in a total loss of filtrate flow i.e. obstruction. This work demonstrates the interplay between the bacterial and host aspects, indicating how factors such as filtration may affect bacterial adhesion and vice versa. It also highlights the multifactorial basis of kidney infection, demonstrating how physiological injuries such as obstruction may contribute towards the full pathophysiology of pyelonephritis.

[Comparative analysis of the role of individual peculiarities of kidney structure in predisposition to the nephrotoxicity of gentamicin in intact and hydronephrotic rabbits]

Comparative analysis of relationships between individual peculiarities of the structure of nephrons in intact and hydronephrotic right rabbit kidneys, on one hand, and the degree of expression of nephrotoxicity of gentamicin with respect to the only intact and as well hydronephrotic left kidney, on the other hand, was undertaken. Damage of the kidney by this antibiotic is more expressed in rabbits with smaller diameter of distal convoluted tubules of nephrons and smaller size of the cells lining their lumen. These peculiarities of the structure of nephrons lead to predisposition to the gentamicin-induced nephropathy in intact rabbits to a higher degree than in animals with hydronephrosis. The method of predicting individual predisposition to gentamicin-induced nephropathy has been patented (No. 7722 of 13.10.2005).

Maternal protein restriction leads to hyperresponsiveness to stress and salt-sensitive hypertension in male offspring

Low birth weight humans often exhibit hypertension during adulthood. Studying the offspring of rat dams fed a maternal low-protein diet is one model frequently used to study the mechanisms of low birth weight-related hypertension. It remains unclear whether this model replicates key clinical findings of hypertension and increased blood pressure responsiveness to stress or high-salt diet. We measured blood pressure via radiotelemetry in 13-wk-old male offspring of maternal normal- and low-protein dams. Neither group exhibited hypertension at baseline; however, 1 h of restraint was accompanied by a significantly greater blood pressure response in low-protein compared with normal-protein offspring. To enhance the effect of a high-salt diet on blood pressure, normal- and low-protein offspring underwent right uninephrectomy, while controls underwent sham surgery. After 5 weeks on a high-salt diet (4% NaCl), mean arterial pressure in the Low-Protein+Sham offspring was elevated by 6 +/- 2 mmHg (P < 0.05 vs. baseline), while it remained unchanged in the normal-protein offspring. In the two uninephrectomized groups, blood pressure increased further, but was of similar magnitude. Glomerular filtration rate in the low-protein uninephrectomized offspring was 50% less than that in normal-protein offspring with intact kidneys. These data indicate that, while male low-protein offspring are not hypertensive during young adulthood, their blood pressure is hyperresponsive to restraint stress and is salt sensitive, and their glomerular filtration rate is more sensitive to hypertension-causing insults. Collectively, these may predispose for the development of hypertension later in life.

Drug-induced nephrotoxicity

Drugs are a common source of acute kidney injury. Compared with 30 years ago, the average patient today is older, has more comorbidities, and is exposed to more diagnostic and therapeutic procedures with the potential to harm kidney function. Drugs shown to cause nephrotoxicity exert their toxic effects by one or more common pathogenic mechanisms. Drug-induced nephrotoxicity tends to be more common among certain patients and in specific clinical situations. Therefore, successful prevention requires knowledge of pathogenic mechanisms of renal injury, patient-related risk factors, drug-related risk factors, and preemptive measures, coupled with vigilance and early intervention. Some patient-related risk factors for drug-induced nephrotoxicity are age older than 60 years, underlying renal insufficiency (e.g., glomerular filtration rate of less than 60 mL per minute per 1.73 m2), volume depletion, diabetes, heart failure, and sepsis. General preventive measures include using alternative non-nephrotoxic drugs whenever possible; correcting risk factors, if possible; assessing baseline renal function before initiation of therapy, followed by adjusting the dosage; monitoring renal function and vital signs during therapy; and avoiding nephrotoxic drug combinations.