Histopathological and ultrastructural studies of gentamicin administration in zinc-deficient guinea pigs

Weanling guinea-pigs were given Zn-deficient (ZnD) or Zn-adequate (ZnA) diets, containing 1.03 or 52.4 mg Zn/Kg, respectively. After 5 weeks, the animals of each dietary group were injected gentamicin sulphate @ 4 mg/kg body weight intramuscularly, daily for 7 days. Two days after the last injection of gentamicin, kidney function tests and pathological studies were conducted to assess the effects of gentamicin administration in relation to Zn deficiency. Gentamicin administration in both the dietary groups resulted in increase serum values of creatinine and urea nitrogen but the magnitude of the increase was higher in ZnD animals. Serum and kidney gentamicin concentrations were significantly higher in ZnD animals as compared to ZnA animals. Histopathologically, gentamicin induced renal tubular degeneration in ZnA animals whereas in ZnD animals, there were necrotic changes in renal tubules and internal ears. Electron microscopy revealed alterations in sub cellular components of renal and hepatic cells due to gentamicin administration in both the dietary groups but these were more severe in ZnD animals. It is concluded that the Zn deficiency enhances toxicity of gentamicin.