[Functional changes in the cochlea of guinea pigs in chronic renal failure--electrocochleography. Effect of noise exposure].

An animal model of chronic renal failure (CRF) was created by the 5/6 nephrectomy procedure in guinea pigs. Levels of serum Cr and BUN were abnormally elevated at 1,2 and 3 months after the procedure. ECoG (CAP, CM) was recorded through a silver ball electrode placed on the round window 1,2 and 3 months after surgery. EP was measured with a glass microelectrode from the scala media via the round window membrane. Only slight ECoG changes were seen 1 month after surgery. On the other hand, moderate or profound changes were observed 2 and 3 months after-surgery. No significant decrease in EP was found in the post-surgery animals which distinctly showed abnormal CAP, CM, although a limited number of animals were studied. The above results indicate that CRF is one of the etiological factors of cochlear dysfunction and the sensory hair cells appeared to be the site of the lesion. To study the interaction between noise exposure and CRF, 1 month post-surgery animals with only a little change in ECoG were exposed to a broad band noise. Changes in the ECoGs were followed up for 6 hours after the noise exposure. In contrast to the controls, animals with CRF did not recover from the reduced ECoG which occurred immediately after the noise exposure. This suggests synergistic interaction between noise and CRF.