 aminoglycoside - induced proteinuria may result from general renal damage or may reflect alterations in specific steps in the renal handling of proteins . to differentiate between the two possibilities , 
 experiments were designed to quantify the effects of nephrotoxic doses of gentamicin , tobramycin and netilmicin in the intact rat , isolated perfused rat kidney ( ipk ) and kidney slices using the cationic low molecular weight protein lysozyme as a model protein . 
 each aminoglycoside was administered ip to male wistar rats ( 15 or 30 mg / kg / day ) for 5 or 7 days . 
 scanning and transmission electron microscopy indicated that gentamicin and tobramycin induced a decrease in the number and diameter of endothelial fenestrae and degranulation of the myoepithelioid cells of the juxtaglomerular apparatus . 
 concurrently , gentamicin and tobramycin decrease the glomerular sieving coefficient of lysozyme from 0.8 to 0.6 and 0.5 , respectively . 
 netilmicin did not affect the percentage reabsorption of lysozyme whereas gentamicin and tobramycin induced a 50% decrease in lysozyme reabsorption by the ipk . 
 gentamicin and tobramycin decreased equally lysozyme degradation by the ipk ; this decrease was time- and dose - dependent when evaluated in slices from renal cortex . 
 perfusion of rat kidneys with gentamicin induced a dose - dependent decrease in reabsorption and catabolism of lysozyme . in conclusion , these studies demonstrate that polycationic aminoglycosides alter ultrastructure and glomerular permeability , tubular reabsorption and intracellular digestion of proteins.imagesfigure 2.figure 3 . 
 ( a)figure 3 . 
 ( b ) 
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