The effect of thyroxine or carbimazole treatment on gentamicin nephrotoxicity in rats

1 This study examines the effect of treating rats with gen tamicin (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 (T₃) was unaffect ed by graded doses (20, 40 and 80 mg kg-1) of the antibiot ic. Histopathologically, gentamicin produced necrosis of proximal tubules in the renal cortical tissues of treated rats. 3 Treatment of rats with either L-thyroxine or carbima zole alone did not significantly affect any of the biochemi cal variables investigated. Carbimazole alone produced only mild tubular necrosis. 4 Treatment of rats with either L-thyroxine (100 μg kg-1 day-1, subcutaneously) for 10 days, and gentamicin (80 mg kg-1, i.m. daily during the last 6 days of treatment signifi cantly 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 signifi cantly affect the gentamicin-induced changes in serum creatinine or cortical N+,K+ATPase.