Aminoglycoside Nephrotoxicity/ Induction of Nephrotoxicity by Gentamicin

Gentamicin is an antibiotic that exhibits a broad spectrum of (Gram –ve) activity and is particularly valuable in several sepsis in animals and humans. Nephrotoxicity and ototoxicity has been recognized as a major complication of aminoglycoside antibiotics for many years. Gentamicin causes reversible renal impairment. The incidence of renal failure is 10-15 % (Naidu et al., 2000) and 10-20 % (Silan et al., 2007) of therapeutic courses. The present study aims at studying the nephrotoxic effect of gentamicin at one high dose (40 mg/kg). The 12 Wistar Albino rats were divided into 2 equal groups (Control and Gentamicin group). Plasma creatinine and BUN concentration was significantly increased as a result of nephrotoxicity. The clinical signs such as dullness, inappetance, increased water intake and increased urination was also observed. Proximal tubular necrosis, vacuolation, desquamation and degeneration in epithelial cells of the proximal tubules, hyaline casts in tubular lumen, mononuclear cell infiltration, glomerular and basement membrane alterations were histopathologically detected in kidney in gentamicin group. In conclusion, gentamicin has adverse effect in kidney.


INTRODUCTION
Gentamicin is a cheap important and widely used antibiotic of aminoglycoside, derived from Micromonospora purpurae. It is used in life threatening gram negative infection. The chemical stability and rapid bactericidal action have made it a drug of choice in a variety of clinical situation. The major complication gentamicin is nephrotoxicity and ototoxicity. Gentamicin causes reversible renal impairment in 10-20 % of patients treated. The exact mechanism of gentamicin induced nephrotoxicity is not clear. It has been shown to enhance the generation of reactive oxygen species (ROS). ROS have been suggested as the causative agent of cell death in different pathological condition including renal diseases /renal failure. The present work aimed to evaluate histological and biochemical alterations in gentamicin induced nephrotoxicity in rats.

MATERIALS AND METHODS Chemicals
Gentamicin Sulphate -40mg/ml was used in this study. Animals Twelve adult Wistar albino rats weighing approximately 150-200g and aged were used in this experimental study. Rats were provided form LAM (Laboratory Animal Medicine) unit, Madhavaram. The rats were housed in plastic cages and fed with ad libitum feed and water throughout the experiment.

Experimental design
Rats were divided randomly into 2 equal groups including six animals each.

Group 1
Control group: NS (same volume of GS) S/C for 15 days.

Sample collection
The blood samples were collected intraocularly at week 1 and 2 for estimation of BUN and creatinine. After 2 weeks, the animals were sacrificed and kidneys were collected for histopathological analysis.
The kidney of animals in which mortality noticed due to induction of nephrotoxicity was used for histopathological analysis.

Biochemical analysis
The level of BUN and creatinine was estimated using Autospan ® diagnostic kit. The BUN and creatinine was estimated by DNPH colorimetric method (Reitman & Frankel, 1957).

Statistical analysis
The mean values of different group were presented as Mean ± SE difference between the mean values were estimated using one way ANOVA.

RESULT AND DISCUSSION Clinical Observations
Induction of nephrotoxicity by gentamicin showed reduced activity, reduced feed intake and increased water intake in rats. Reduced activity and concentrated urine output may be due to the occurrence of renal dysfunction. Loss of appetite, anorexia, increased catabolism and acidosis in gentamicin induced acute renal failure in rats may be the reasons for reduced feed intake (Erdem et al., 2000). Haemodilution may be involved in the fall of sodium value via excess water intake and/or increased production of endogenous water (Mohammed et al., 2016).

Biochemical alterations
The mean BUN and Creatinine value of treatment groups are presented in Table 2 and Table 3 respectively. The significant increase in plasma BUN and creatinine when compared with control group indicate the occurrence of nephrotoxicity. The plasma creatinine concentration is more potent indicator than the urea concentration in first phase of kidney diseases. Urea (Yaman, I and E. Balikci, 2010) concentration begins to increase only after parenchyma tissue injury (Gilbert et al., 1989).The elevated BUN is due to protein catabolism. The high level of blood urea noted due to increase breakdown of tissue or impaired excretion. There is increase in BUN and creatinine level after kidney fail to remove them and other waste products from blood (Mohamed et al., 2011). Week 1 0.51 a ± 0.02 0.83 b ± 0.03 Week 2 0.52 a ± 0.02 1.18 b ± 0.08

Histopathological alterations
Histopathological analysis showed that there was significant increase in renal damage in gentamicin treated groups. Sections from control group showed normal histological structure of the glomeruli and renal tubules in the cortex and normal tubules in medulla (Abdel-Raheem et al., 2009) and it is presented in Figure 1. The histopathology of kidney from gentamicin treated rats is presented in Figure  2. It displayed necrosis and desquamation of the tubular epithelial cell in renal cortex (Kaloyanides & Pastoriza-Munoz, 1980). The proximal tubules showed degeneration of epithelial lining with disruption of their brush borders and presence of epithelial debris in lumen the renal corpuscles showed degeneration of in glomerulus and disputed Bowmans capsules vacuolation and mononuclear cell infiltration (Azab et al., 2014). The finding of present study is similar to above findings.

Histopathology of kidney CONCLUSION
According to this study the clinical observations, biochemical and histopathological changes reveal that the gentamicin induces nephrotoxicity. Many herbs such as curcumin, rosemary, Nigella sativa, Ginkgo biloba, garlic and Tecoma stans found to have nephroprotective effect against gentamicin induced nephrotoxicity. The use of aminoglycosides antibiotics must be regulated by administering it for specifically required cases after doing ABST or MIC. The