Calcium supplementation and thyroid hormone protect against gentamicin-induced inhibition of proximal tubular Na+,K(+)-ATPase activity and other renal functional changes

Protective Effects of Descurainia sophia against Gentamicin Induced Nephrotoxicity in Rats

Several studies have tried to find an efficient agent to prevent or reverse gentamicin (Gm) induced acute kidney injury (AKI). In this study, we assessed the potential renal protective effects of Descurainia sophia (L.) Webb ex Prantl against Gm-induced nephrotoxicity in rats. Thirty-five male Wistar rats were categorized in five groups (n = 7 per group). Control group was treated with normal saline. In four experimental groups, the rats were initially treated with normal saline (A), 800 (B), 1600 (C) and 2400 (D) mg/kg Descurainia sophia respectively for 28 days. After that, the rats of experimental groups were treated with Gm (80 mg/Kg) for 7 consecutive days. Blood and urine markers, as well as apoptosis and histological features were determined. Serum BUN, creatinine, cholesterol, and triglycerides level, as well as urinary excretion of Na⁺ significantly increased in group A. Furthermore, Gm induced inflammatory cells infiltration, apoptosis, and renal cells injuries in rats were pretreated with normal saline (group A). However, in the rats pretreated with Descurainia sophia extract (groups B, C, and D, there were significant and dose-dependent reductions in serum BUN, creatinine, cholesterol and triglyceride, urinary Na⁺ excretion, apoptosis rate, and inflammatory cells infiltration in renal tissues. Overall, Descurainia sophia showed significant protective effects against Gm-induced AKI by alleviating biochemical and histological markers of renal toxicity.

Thyroid Hormone Treatments Differentially Affect the Temperature Kinetics Properties of FoF1 ATPase and Succinate Oxidase as well as the Lipid/Phospholipid Profiles of Rat Kidney Mitochondria: A Correlative Study

Effect of thyroidectomy (Tx) and subsequent treatment with 3,5,3'-triiodo-L: -thyronine (T(3)) or replacement therapy (T(R)) with T(3)+ L: -thyroxine (T(4)) on the temperature kinetics properties of FoF(1 )adenosine triphosphatase (ATPase, ATP synthase, H(+)-translocating ATP synthase EC 3.6.3.14) and succinate oxidase (SO) and on the lipid/phospholipid makeup of rat kidney mitochondria were examined. Tx lowered ATPase activity, which T(3) treatment restored. SO activity was unchanged in Tx but decreased further by T(3) treatment. T(R )restored both activities. The energies of ATPase activation in the high and low temperature ranges (E (H) and E (L)) increased in the Tx and T(3) animals with decrease in phase transition temperature (Tt). T(R) restored E (H) and E (L) but not Tt to euthyroid levels. E (H) and E (L) of SO decreased in Tx animals. T(3) and T(R) restored E (H) whereas E (L) was restored only in the T(R) group; Tt increased in both groups. Total phospholipid and cholesterol contents decreased significantly in Tx and T(3)-treated animals. In Tx animals, sphingomyelin (SPM) and phosphatidylcholine (PC) components decreased, while phosphatidylserine (PS) and diphosphatidylglycerol components increased. T(3) and T(R) treatments caused decreases in SPM, phosphatidylinositol and PS. PC and phosphatidylethanolamine (PE) increased in the T(3) group. T(R) resulted in increased lysophospolipids and PE. Changes in kinetic parameters of the two enzymes were differently correlated with specific phospholipid components. Both T(3) and T(R) regimens were unable to restore normal membrane structure-function relationships.

Effect of spironolactone on cisplatin-induced nephrotoxicity in rabbits

The effects of a single interaperitoneal dose of cisplatin (6.5 mg kg day(-1)), oral doses of spironolactone (20.0 mg kg day(-1)) for 5 days or the combined treatment (spironolactone+cisplatin) on the kidney function and liver function parameters, as well as the serum, liver and kidney cortical lipid contents were studied. The serum urea and creatinine concentrations (measured as kidney function parameters) were not altered by spironolactone treatment, but were significantly (P<0.001) elevated by cisplatin administration. However, animals exposed to both spironolactone+cisplatin revealed drastic increases in the serum creatinine and urea concentrations amounting to about four- and twofold those of cisplatin-alone treated animals, respectively. The histological examination of slides of kidneys from animals exposed to the combined drugs exhibited more extensive necrosis in the tubules compared to those from animals treated with cisplatin alone. Non of the drug treatments had any effects on the serum alanine transaminase (ALT) and aspartate transaminase (AST) levels (measured as liver function parameters) or liver protein content or hepatic alkaline phosphatase (ALP) activity. The histological examination also revealed apparently normal livers in all experimental groups. The cisplatin-induced nephrotoxicity was accompanied by hypercholesterolaemia and hyperphospholipidaemia, whereas spironolactone showed a hypocholesterolaemic effect. The concomitant treatment with both cisplatin and spironolactone significantly (P<0.05) raised the serum triacylglycerol (TAG) concentration compared to the cisplatin-alone-treated group. Both spironolactone and cisplatin administered separately or jointly caused accumulation of cholesterol and TAG in the kidney cortex with significant depletion of the liver cholesterol content. The present results indicated that spironolactone aggravates the cisplatin-induced nephrotoxicity in the rabbit.

Localization of the nephron site of gentamicin-induced hypercalciuria in the rat: a micropuncture study

In vivo renal micropuncture techniques were used to locate the nephron site of hypercalciuria induced by acute gentamicin infusion in anaesthetized Sprague Dawley rats. Three series of experiments were conducted. The effect of gentamicin on calcium reabsorption in the proximal tubule (Series I) and loop of Henle (Series II) was investigated using in vivo microperfusion whereas the effect on distal calcium handling (Series III) was studied using in vivo microinfusion. In all three experimental series, acute systemic gentamicin infusion at 0.28 mg kg(-1) min(-1) caused significant hypercalciuria within 30 min of commencing drug infusion. Gentamicin had no effect on the rates of urine flow or sodium excretion. Acute gentamicin infusion had no effect on unidirectional calcium reabsorption in the proximal tubule or loop of Henle despite a simultaneous and highly significant hypercalciuria at the whole kidney level. Net fluid reabsorption was also unaffected by the drug in these nephron segments. Acute gentamicin infusion significantly increased the urinary recovery of calcium following microinfusion into early distal tubules, whereas urinary calcium recovery was decreased after microinfusion into late distal tubules. We conclude that acute gentamicin-induced hypercalciuria is mediated by a decrease in calcium reabsorption in the early distal tubule. Thus, the acute hypercalciuric effect of gentamicin occurs at a different nephron site to the nephrotoxic effects associated with longer-term administration of the drug. It is, therefore, unlikely that gentamicin-induced hypercalciuria is involved in the pathogenesis of subsequent proximal tubular cell injury.

Effect of acetaminophen on Na(+), K(+) ATPase and alkaline phosphatase on plasma membranes of renal proximal tubules

In previous work we reported that 1 h after acetaminophen (APAP) administration, tubular function remained at control values, while 16 h later a significant deterioration of tubular function was observed. The aim of the present work was to study if APAP induces its renal toxic effects by altering the normal activity of key tubular plasma membrane enzymes. We analyzed the effects of a nephrotoxic dose of APAP (1000 mg/kg b.wt., i.p.) on the activities of the brush-border membrane (BBM) enzyme, alkaline phosphatase, and the basolateral membrane (BLM) enzyme Na(+), K(+) ATPase 1 h (APAP(1h)) and 16 h (APAP(16h)) after dosing. Na(+), K(+) ATPase abundance in homogenates and each membrane domain were analyzed by Western blot. Cortical adenosine 5' triphosphate (ATP) content was also evaluated. At each time studied, APAP promoted a diminution of alkaline phosphatase in BBM. Na(+), K(+) ATPase activity in BLM showed a biphasic response to APAP. One hour after APAP administration it was significantly increased, but it was decreased 16 h after dosing. Na(+), K(+) ATPase protein abundance was elevated in homogenates, BLM, and BBM after 1 h of APAP dosing. After 16 h, Na(+), K(+) ATPase abundance was increased in homogenates, while in BLM it was decreased. No differences were observed in cortical ATP content in each time studied. Our present results could contribute to the understanding of the molecular basis of the previously reported time course alteration in the fractional excretion of sodium promoted by a nephrotoxic dose of APAP.

Effect of experimental diabetes mellitus on gentamicin-induced acute renal functional changes in the anaesthetized rat

1. Rats with streptozotocin (STZ) diabetes are protected from gentamicin (GEN) nephrotoxicity. Because the chronic renal damage from GEN is preceded by acute renal functional changes (notably hypercalciuria), the present study aims to determine whether diabetes may also protect against the acute effects of the drug. If there is a link between the rapid physiological actions of GEN and its subsequent nephrotoxicity, the former may also be affected by the diabetic condition. 2. Standard renal clearance techniques were performed on anaesthetized rats that had been injected with STZ or vehicle 2 weeks previously. All animals were infused with 0.9% NaCl for 5 h and then either GEN (0.28 mg/kg per min) or 0.9% NaCl alone for 2 h. 3. Baseline fractional calcium excretion (FE(Ca)) of diabetic rats was three-fold that of control animals (6.6+/-0.2 vs 2.2+/-0.2%, respectively; P<0.01, MANOVA). Following GEN infusion, a comparable increase in FE(Ca) occurred in control and diabetic rats (5.3+/-0.6 vs 5.3+/-0.8%, respectively; NS). 4. Streptozotocin diabetes, therefore, does not alter the acute hypercalciuric response to GEN. This may suggest that the acute effects of GEN on renal calcium handling do not contribute to the subsequent nephrotoxicity. However, the higher baseline FE(Ca) seen in diabetic rats may afford protection against the renal injury caused by gentamicin.

Effects of fish oil and sunflower oil supplementations on gentamicin-induced nephrotoxicity in rat

1. Nephrotoxicity was induced in rats by intramuscular administration of gentamicin (80 mg k-1 d-1) for 6 days. 2. Oral supplementation with fish oil (5 ml kg-1 d-1), for 2 weeks prior to and during gentamicin exposure, markedly ameliorated the drug-induced nephrotoxicity. The beneficial effects of oil were evidenced by significantly reduced serum creatinine and urea concentrations, increased renal cortical alkaline phosphatase activity and improved renal tubular histology, compared with the non oil-treated animals, receiving gentamicin. 3. Similar supplementation with sunflower oil, rich in omega-6 fatty acids, failed to reverse any of the parameters of nephrotoxicity induced by gentamicin. 4. Hypercholesterolaemia and reduced cortical GSH associated with gentamicin nephrotoxicity were both normalised by supplementation with fish oil, but not by sunflower oil. 5. The beneficial effects of fish oil on gentamicin-induced nephrotoxicity were not related to the extent of uptake and accumulation of the drug by the kidney.

Gentamicin nephrotoxicity in humans and animals: some recent research

It would appear from the literature cited in this article, that interest in gentamicin nephrotoxicity is still thriving. Despite extensive studies, the mechanism(s) of the nephrotoxicity is uncertain. Several clinical and experimental strategies have been employed in order to ameliorate or abolish the signs of gentamicin nephrotoxicity. Most of these were unsuccessful, impractical or unsafe. Therefore there is still a need for further studies to elucidate the mechanism(s) of action of the drugs nephrotoxicity, and to discover safe, practical and effective agents to ameliorate the nephrotoxicity in patients at risk.

The effect of thyroxine or carbimazole treatment on gentamicin nephrotoxicity in rats

1. This study examines the effect of treating rats with gentamicin (80 mg kg-1 day-1 intramuscularly (i.m.), for 6 days) alone or with either L-thyroxine or the anti-thyroid drug carbimazole. 2. Gentamicin produced significant increases in serum creatinine and urea concentrations, and significantly reduced the activity of Na+,K+ATPase in renal cortex. The concentration of serum triiodothyronine (T3) was unaffected by graded doses (20, 40 and 80 mg kg-1) of the antibiotic. Histopathologically, gentamicin produced necrosis of proximal tubules in the renal cortical tissues of treated rats. 3. Treatment of rats with either L-thyroxine or carbimazole alone did not significantly affect any of the biochemical variables investigated. Carbimazole alone produced only mild tubular necrosis. 4. Treatment of rats with either L-thyroxine (100 micrograms kg-1 day-1, subcutaneously) for 10 days, and gentamicin (80 mg kg-1, i.m. daily during the last 6 days of treatment significantly reduced the gentamicin-induced increases in serum creatinine and urea concentrations, and increased the activity of cortical N+,K+ATPase to control levels. Histopathologically, the severity of gentamicin-induced tubular necrosis was reduced by L-thyroxine treatment. 5. Carbimazole (12 mg ml-1 in drinking water for 21 days) and gentamicin (80 mg kg-1 i.m.) daily during the last 6 days of treatment, stimulated the increase in serum urea concentration produced by gentamicin, but did not significantly affect the gentamicin-induced changes in serum creatinine or cortical N+,K+ATPase.

Renal handling of drugs and amino acids after impairment of kidney or liver function--influences of maturity and protective treatment

Renal tubular cells are involved both in secretion and in reabsorption processes within the kidney. Normally, most xenobiotics are secreted into the urine at the basolateral membrane of the tubular cell, whereas amino acids are reabsorbed quantitatively at the luminal side. Under different pathological or experimental circumstances, these transport steps may be changed, e.g., they may be reduced by renal impairment (reduction of kidney mass, renal ischemia, administration of nephrotoxins) or they may be enhanced after stimulation of transport carriers. Furthermore, a distinct interrelationship exists between excretory functions of the kidney and the liver. That means liver injury can influence renal transport systems also (hepato-renal syndrome). In this review, the following aspects were included: based upon general information concerning different transport pathways for xenobiotics and amino acids within kidney cells and upon a brief characterization of methods for testing impairment of kidney function, the maturation of renal transport and its stimulation are described. Similarities and differences between the postnatal development of kidney function and the increase of renal transport capacity after suitable stimulatory treatment by, for example, various hormones or xenobiotics are reviewed. Especially, renal transport in acute renal failure is described for individuals of different ages. Depending upon the maturity of kidney function, age differences in susceptibility to kidney injury occur: if energy-requiring processes are involved in the transport of the respective substance, then adults, in general, are more susceptible to renal failure than young individuals, because in immature organisms, anaerobic energy production predominates within the kidney. On the other hand, adult animals can better compensate for the loss of renal tissue (partial nephrectomy). With respect to stimulation of renal transport capacity after repeated pretreatment with suitable substances, age differences also exist: most stimulatory schedules are more effective in young, developing individuals than in mature animals. Therefore, the consequences of the stimulation of renal transport can be different in animals of different ages and are discussed in detail. Furthermore, the extent of stimulation is different for the transporters located at the basolateral and at the luminal membranes: obviously the tubular secretion at the contraluminal membrane can be stimulated more effectively than reabsorption processes at the luminal side.