Acute effects of combined administration of kanamycin and furosemide on the stria vascularis studied by distortion product otoacoustic emission and transmission electron microscopy

Acute effects of kanamycin and/or furosemide administration on the stria va scularis of the guinea pig cochlea were assessed by distortion product otoa coustic emission (DPOAE) and transmission electron microscopy. Kanamycin al one failed to affect the DPOAE levels and ultrastructural changes. Furosemi de alone caused a rapid but reversible fall of the DPOAE levels. No remarka ble pathological changes in the strial vascularis were observed after a com plete recovery of the DPOAEs. On the other hand, furosemide injection follo wing kanamycin with a 2 hour interval resulted in two patterns of significa nt changes in the DPOAEs, namely, a sudden drop in the DPOAE levels 2 to 3 hours after furosemide injection and a gradual fall in the DPOAE levels imm ediately after the incomplete recovery from the furosemide-induced decrease of the DPOAE levels. Ultrastructural changes in the stria vascularis inclu ded numerous vacuoles in the strial marginal cells and increased electron d ensity of the intermediate and basal cells. These physiological and morphol ogical changes in the stria vascularis may imply new ototoxic features indu ced by kanamycin potentiated by furosemide.