Improved sodium hydroxide digestion method without homogenization for extraction of gentamicin from renal tissue

Renoprotective effects of the direct renin inhibitor aliskiren on gentamicin-induced nephrotoxicity in rats

This study aimed to examine the protective effects of aliskiren on gentamicin-induced nephropathy. Rats were injected with gentamicin (100 mg/kg per day) for 14 days. Aliskiren was infused for two weeks. Human proximal tubular epithelial cell lines (HK-2) were cultured with gentamicin in the absence or presence of aliskiren. Inflammatory profibrotic and apoptotic markers were evaluated in vivo and in vitro. Aliskiren treatment attenuated the decreased creatinine clearance, increased fractional sodium excretion, glomerulosclerosis and tubulointerstitial fibrosis and counteracted the increased ED-1 expression in gentamicin-treated rats. The levels of inflammatory cytokines (TNF-α, IL-1β and IFN-γ) and adhesion molecules (MCP-1, ICAM-1 and VCAM-1) increased in the gentamicin-treated kidneys. These changes were restored by aliskiren co-treatment. Aliskiren effectively reversed transforming growth factor-β-induced fibrotic responses such as induction of α-smooth muscle actin in gentamicin-treated rat kidneys. Along with these changes, aliskiren also attenuated the increase in nuclear factor κB and phosphorylated extracellular signal-regulated kinase (pERK 1/2) levels in HK-2 cells cultured with gentamicin. In addition, aliskiren decreased the number of TUNEL-positive nuclei and reduced the expression of proapoptotic markers in gentamicin-treated HK-2 cells. These findings suggest that aliskiren attenuates gentamicin-induced nephropathy by suppression of inflammatory, profibrotic and apoptotic factors through inhibition of the nuclear factor κB, Smads and mitogen-activated protein kinase signaling pathways.

Effect of platelet activating factor antagonist treatment on gentamicin nephrotoxicity

To assess whether PAF could be involved in the gentamicin-induced nephrotoxicity, we have studied the effect of PAF antagonist BN-52021 on renal function in rats after gentamicin (GENTA) treatment. Experiments were completed in 21 Wistar rats divided into three groups: group GENTA was injected with gentamicin 100 mg kg⁻¹ body wt/day s.c. for 6 days. Group GENTA + BN received gentamicin and BN-52021 i.p. 5 mg kg⁻¹ body wt/day. A third group served as control. Rats were placed in meta-bolic cages and plasma creatinine and creatinine clearance were measured daily. GENTA group showed a progressive increase in plasma creatinine, a drop in creatinine clearance and an increase in urinary excretion of N-acetyl-β-D-glucosaminidase and alkaline phosphatase. GENTA + BN group showed a lesser change in plasma creatinine and a creatinine clearance, but no difference with GENTA group in urinary excretion of NAG and AP were observed. Histological examination revealed a massive cortical tubular necrosis in rats treated with gentamicin, whereas in BN-52021 injected animals tubular damage was markedly attenuated. The present results suggest a role for PAF in the gentamicininduced nephro-toxicity.

Factors Affecting Gentamicin Penetration in Lower Extremity Ischemic Tissues With Ulcers

The aims of the study were to analyze the penetration of gentamicin in foot ulcers in patients with different severities of peripheral arterial disease (PAD) and to determine significant parameters affecting lower limb tissue concentrations. Patients undergoing debridement of a wound or an amputation procedure were included. All patients received a 120 mg or 240 mg intravenous dose of gentamicin prior to the procedure. Patients were classified according to the degree of PAD. Tissue and serum samples were collected at the time of intervention, and gentamicin concentrations were determined by fluorescence polarization immunoassay. Blood and tissue samples were taken from 61 patients, 41 males and 20 females with a mean age of 66 years. Nineteen patients had nil or borderline PAD, 9 patients had mild or moderate PAD, and 26 patients had severe PAD. Forty-eight patients had type 2 diabetes, 8 patients had type 1 diabetes, and 5 patients were nondiabetic. The concentration of gentamicin in peripheral skeletal muscle tissue was dependent on the serum concentration, degree of PAD, gender, and age. For patients with ischemic lower extremity wounds (patients with mild, moderate, and severe PAD), the concentration of gentamicin was significantly lower ( P = .010) than the concentration in nonischemic wounds, and the concentration in female patients was also significantly lower than in male patients ( P = .047). The concentration in peripheral subcutaneous tissue was 0.663 times the concentration in skeletal muscle tissue ( P < .00001). Gentamicin showed greatest penetration in male patients without PAD. For patients with severe PAD, higher doses of gentamicin may be required to achieve the same effect.

Renoprotective effects of paricalcitol on gentamicin-induced kidney injury in rats

Vitamin D is thought to exert a protective effect on renal disease progression, but the underlying molecular mechanism remains unclear. We investigated whether paricalcitol ameliorates tubular dysfunction and fibrosis in gentamicin (GM)-induced renal injury. Two groups of rats were treated with GM (100 mg x kg(-1) x day(-1)), one of which was cotreated with paricalcitol (0.3 microg x kg(-1) x day(-1)) for 14 days and the other was not. The control group was treated with vehicle only. HK-2 cells were cultured with GM in the absence or presence of paricalcitol. Paricalcitol restored impaired renal function and the downregulated renal sodium transporters and aquaporin-1 expression caused by GM. ED-1-expressing monocyte/macrophage accumulation induced by GM was attenuated by paricalcitol treatment. Paricalcitol prevented upregulated inflammatory cytokines (TNF-alpha, IL-1beta, INF-gamma) and adhesion molecules (monocyte chemoattractant protein-1, ICAM-1, VCAM-1) induced by GM. In addition, paricalcitol effectively reversed TGF-beta1-induced epithelial-to-mesenchymal transition (EMT) process and extracellular matrix accumulation in GM-induced nephropathy. Increased collagen deposition and fibrosis in GM-treated kidney were ameliorated by paricalcitol. Paricalcitol also attenuated the upregulated NF-kappaB and phosphorylated ERK1/2 expression in HK-2 cells cultured with GM. In conclusion, paricalcitol prevents GM-induced renal injury by inhibiting renal inflammation and fibrosis, the mechanism of which is the interruption of NF-kappaB/ERK signaling pathway and preservation of tubular epithelial integrity via inhibiting EMT process.

Poly-L-aspartic acid enhances and prolongs gentamicin-mediated suppression of the CFTR-G542X mutation in a cystic fibrosis mouse model

Aminoglycosides such as gentamicin have the ability to suppress translation termination at premature stop mutations, leading to a partial restoration of protein expression and function. This observation led to studies showing that this approach may provide a viable treatment for patients with genetic diseases such as cystic fibrosis that are caused by premature stop mutations. Although aminoglycoside treatment is sometimes associated with harmful side effects, several studies have shown that the co-administration of polyanions such as poly-L-aspartic acid (PAA) can both reduce toxicity and increase the intracellular aminoglycoside concentration. In the current study we examined how the co-administration of gentamicin with PAA influenced the readthrough of premature stop codons in cultured cells and a cystic fibrosis mouse model. Using a dual luciferase readthrough reporter system in cultured cells, we found that the co-administration of gentamicin with PAA increased readthrough 20-40% relative to cells treated with the same concentration of gentamicin alone. Using a Cftr-/- hCFTR-G542X mouse model, we found that PAA also increased the in vivo nonsense suppression induced by gentamicin. Following the withdrawal of gentamicin, PAA significantly prolonged the time interval during which readthrough could be detected, as shown by short circuit current measurements and immunofluorescence. Because the use of gentamicin to suppress disease-causing nonsense mutations will require their long term administration, the ability of PAA to reduce toxicity and increase both the level and duration of readthrough has important implications for this promising therapeutic approach.

Validation of two enzyme immunoassays for aminoglycoside residues according to European Decision 657/2002

Aminoglycoside antibiotics are commonly used to treat bacterial infections in human and veterinary practice. Owing to their toxicity, the European Community has established maximum residue limits (MRL) in foodstuffs of animal origin (EEC No 2377/90). In the present study, the performance of two new enzyme immunoassays (EIA), I'screen Gentamicin and I'screen Neomycin, for the quantitative detection of the aminoglycosides, gentamicin and neomycin, in milk and tissue are described. Validation of these EIAs has been performed in accordance to the criteria of European Decision 657/2002. Assays sensitivity at the MRLs was 95% for milk samples and 100% for tissue samples, while specificity was 100% at 33 and 25% of the MRLs for milk and tissues, respectively. The performance of these EIAs indicates that they can be used as easy screening methods for the analysis of aminoglycosides in milk and tissue samples.

The effect of surface charge on the disposition of liposome-encapsulated gentamicin to the rat liver, brain, lungs and kidneys after intraperitoneal administration

The disposition of gentamicin to the normal rat brain, lung, kidney and liver was studied at intervals of 1, 2, 4, 6 and 8h after intraperitoneal injection of gentamicin encapsulated in positive, negative and neutral liposomes. Compared with the control, which was treated with free gentamicin, liposomes were associated with higher concentrations of gentamicin in the brain and liver, while concentrations were lower in the kidney. The average concentrations of gentamicin in the liver and the brain were highest with positive liposomes, while, gentamicin concentrations in the kidneys and lungs were not influenced by surface charge of the liposomes. These observations have important implications on the selective delivery of gentamicin to tissues and on the intraperitoneal route of administration.

Effect of nitric oxide synthesis modification on renal function in gentamicin-induced nephrotoxicity

We evaluated the effect of acute or chronic nitric oxide (NO) synthesis activation or inhibition in rats with gentamicin-induced acute renal failure. Rats received gentamicin 100 mg/kg per day for 6 days, or isotonic saline. Some animals of each group also received N(G)-monomethyl-l-arginine (l-NAME, 4 mg/kg per day) or l-arginine (1%) in the drinking water for 6 days (chronic NO synthesis modification). In another experimental set, animals were treated with gentamicin or saline for 6 days and glomerular filtration rate (GFR) and renal plasma flow (RPF) were measured before and after the infusion of l-NAME (50 mg/h per kg) or l-arginine (60 mg/h per kg) (acute NO synthesis modification). Acute l-NAME administration induced a decrease in GFR and RPF both in control and gentamicin treated animals. Chronic l-NAME treatment induced an impairment in GFR only in gentamicin-treated animals. Acute l-arginine administration did not modify renal function in any experimental group whereas chronic l-arginine administration improved renal function only in gentamicin-treated animals. Urinary excretion of N-acetyl-β-d-glucosaminidase and alkaline phosphatase was increased by chronic treatment with l-NAME in both groups, whereas l-arginine had no effect. In conclusion, NO synthesis inhibition aggravates gentamicin-induced renal damage. However, chronic NO synthesis stimulation partially prevents against gentamicin nephrotoxicity, thus suggesting that increased renal NO synthesis during gentamicin-induced nephrotoxicity plays a protector role on renal function.

Effect of gentamicin treatment on glutamine and lactate metabolism by the renal cortex of the rat

The present study was performed to measure the uptake of main renal cortical fuel substrates (glutamine and lactate) and the release of the main renal cortical products (ammonia and glucose) by cortical slices from gentamicin-treated rats. Experiments were done in 2 groups of female Wistar rats (250 g): In gentamicin group (n = 13), rats were injected s.c. with gentamicin-sulphate 100 mg/Kg body wt/day for 5 days. Control rats (n = 13) received isotonic saline. After anesthesia and blood sampling, renal cortical slices were obtained and incubated with L-glutamine and/or lactate at 1 or 5 mM concentration, containing L-glutamate and/or pyruvate at 0.1 or 0.5 mM. Creatinine clearance was reduced to a 50% in gentamicin-treated rats. In addition these animals showed a sharp increase in urinary excretion of N-acetyl-beta-D-glucosaminidase and alkaline phosphatase. Light microscopy examination revealed extensive cell necrosis and tubular obstruction of the proximal tubules in kidneys of rats injected with gentamicin. The renal cortical gentamicin concentration of rats injected with gentamicin was 310 +/- 43 mu/g, whereas it was undetectable in control rats. Cortical slices from gentamicin-treated rats, compared to control ones, showed a reduced production of ammonia and glucose, without differences in glutamine or lactate extraction. These alterations can be explained by both the increased rate of anabolic reactions to recover cell damage associated to renal failure, as well as by a direct effect of gentamicin on the rate of carboxylation reactions.

The effects of experimentally induced bronchopneumonia on the pharmacokinetics and tissue depletion of gentamicin in healthy and pneumonic calves

The effects of a bovine bronchopneumonia model on the pharmacokinetics and tissue residue depletion profiles of gentamicin in calves weighing 90-140 kg was explored. Two groups of heifer calves were used. The first was a normal group, while the second group had bronchopneumonia induced. A scoring system was developed to evaluate the extent of disease in the groups. A bimodal distribution of the serum pharmacokinetic parameters in the pneumonic group was caused by the effects of dehydration. When the severely dehydrated calves were omitted from the analysis, serum clearance of gentamicin was significantly higher in the pneumonic group than in the normal group (P less than 0.05). The pharmacokinetic equations used to fit the tissue concentrations varied from tissue to tissue and between groups. Because the best equation of a particular tissue's concentrations varied between groups, withdrawal periods, which are normally determined in healthy animals, may be inappropriate in diseased animals. Addition of several parameters (serum creatinine, serum urea nitrogen, albumin, fibrinogen, and total protein concentrations, white blood cell counts, central fluid volume, volume of distribution at steady state, area under the serum concentration vs time curve, serum clearance, and elimination rate constant) to these tissue-depletion models using multiple regression improved the prediction of a concentration in a given tissue.

Comparison of serum and renal gentamicin concentrations with fractional urinary excretion tests as indicators of nephrotoxicity

Gentamicin was given to six sheep at a dosage rate of 80 mg/kg/day divided into three daily doses to cause nephrotoxicity. Peak serum gentamicin concentrations rose significantly throughout dosing (P less than 0.05), but trough serum gentamicin concentrations increased dramatically (P less than 0.01) from initial concentrations of 3.2-9.1 micrograms/ml to final trough concentrations of 31.5-195 micrograms/ml by 6-10 days on gentamicin. The serum gentamicin elimination half-life (t1/2) was doubled in each animal by approximately 6 days on therapy, with the sheep that were the most clinically affected by the nephrotoxic effects of gentamicin showing increases in t1/2 earlier than those sheep that remained less intoxicated. These changes occurred before many other clinical indicators of nephrotoxicity, with only urinary enzyme excretions preceding the changes in gentamicin elimination. Thus, alterations in the elimination of gentamicin may be one of the first clinical indicators of the occurrence of gentamicin-induced nephrotoxicity.