The effect of vitamin D deficiency on the cochlear potentials and the perilymphatic ionized calcium concentration of rats.

Sensorineural hearing loss has been frequently reported in patients with renal failure but its etiology has not yet been established. Disturbance of Ca metabolism is present in renal failure and seems to cause hearing loss. The purpose of the present study was to determine whether the disturbance of Ca metabolism has any effect on cochlear function. The cochlear potentials were measured in 19 rats fed with a vitamin D deficient diet. The pathological findings showed prolongation of N1 latency with unchanged N1 amplitude and pseudothreshold, depression of CM amplitude and elevation of the CM pseudothreshold. The latencies of narrow-band APs were prolonged in the entire cochlear partition. Ca2+ concentration in perilymph was 3.2 X 10(-4) M (n = 4) in vitamin D deficient rats and 7.4 X 10(-4) M (n = 4) in the controls. These findings were milder than those obtained in surgically induced renal failure. It was concluded that although vitamin D deficiency is one cause of hearing loss in renal failure, other major factors must be involved. The authors postulate that hearing loss in vitamin D deficiency is mainly attributable to the depression of the Ca2+ concentration in perilymph.