RESUMEN
Tobramycin is the most active member of all the aminoglycoside antibiotic group acting against gram- negative bacteria. The aim of present study was to detect the effect of tobramycin on tile convoluted tubules in two different dosage regimen. Sixty adult male albino rats were divided into three groups. Group I as control. Group II: included rats which were injected intraperitoneally with daily dose of 4 mg/kg tobramycin in three equally divided doses. Group III: injected with the same previous dose once daily. They were sacrificed after 3,10,14 days of injection and tissue samples from the cortex of each kidney were taken and processed for both light and electron microscopic examination. In group II, by light microscope swelling of the cells lining the convoluted tubules and vacuolation of their cytoplasm as well as brown granules and hemorrhage were observed. The regenerating cells appeared with basophilic cytoplasm. Progressive decrease in succinic dehydrogenase and increase in acid phosphatase enzymatic activities were observed. Ultrastructurally, there were affection of mitochondria and partial or complete loss of microvilli in some tubules were observed. The cytoplasm of some tubules revealed numerous myeloid bodies with various degrees of nuclear degeneration. Dilated basal infoldings and thickened basement membrane was also observed. The previous changes were less evident on administration of the drug in Group III. In conclusion, patients with a previous kidney disease should better avoid the use of this drug whenever possible but if its use is necessary, once daily dosage may be advised for short period