THE EFFECT OF THYROXINE OR CARBIMAZOLE TREATMENT ON GENTAMICIN-NEPHROTOXICITY IN RATS

1 This study examines the effect of treating rats with gentamicin (80 mg kg(-1) day(-1) intramuscularly (i.m.), for 6 days) alone or with either L-thyroxine or the anti-thyroid drug carbimazole. 2 Gentamicin produced significant increases in serum creatinine and urea concentrations, and significantly reduced the activity of Na+,K(+)ATPase in renal cortex. The concentration of serum triiodothyronine (T-3) was unaffected by graded doses (20, 40 and 80 mg kg(-1)) of the antibiotic. Histopathologically, gentamicin produced necrosis of proximal tubules in the renal cortical tissues of treated rats. 3 Treatment of rats with either L-thyroxine or carbimazole alone did not significantly affect any of the biochemical variables investigated. Carbimazole alone produced only mild tubular necrosis. 4 Treatment of rats with either L-thyroxine (100 mu g kg(-1) day(-1), subcutaneously) for 10 days, and gentamicin (80 mg kg(-1), i.m. daily during the last 6 days of treatment significantly reduced the gentamicin-induced increases in serum creatinine and urea concentrations, and increased the activity of cortical N+,K(+)ATPase to control levels. Histopathologically, the severity of gentamicin-induced tubular necrosis was reduced by L-thyroxine treatment. 5 Carbimazole (12 mg ml(-1) in drinking water for 21 days) and gentamicin (80 mg kg(-1) i.m.) daily during the last 6 days of treatment, stimulated the increase in serum urea concentration produced by gentamicin, but did not significantly affect the gentamicin-induced changes in serum creatinine or cortical N+,K(+)ATPase.