Abstract
Effects of long-term hyperlipidemia on the hearing organ have not been studied experimentally in detail, because animals with this condition could not be reliably produced for long periods. Using Watanabe heritable hyperlipidemic (WHHL) rabbits, with serum cholesterol and triglycerides about ten times those of normal rabbits from birth, without special fatty feed, we examined the hearing physiologically by the auditory brain stem response (ABR) with air- and bone-conduction and morphologically by light microscopy and transmission electron microscopy.
The following results were obtained.
1. The bone-conducted ABR threshold of WHHL rabbits (17±8dB (mean±S. D.)) was higher than that of the controls (0±2dB (mean±S. D.)). Morphologically, pathological changes were observed in the outer hair cells and stria vascularis of the WHHL rabbits.
Therefore, WHHL rabbits have sensorineural hearing loss caused by the inner ear damage.
2. The degree of inner ear damage in the WHHL rabbits was severer than that in guinea pigs with alimentary hyperlipidemia reported to date.
3. The transmission electron microscopic changes in the cochlea of WHHL rabbits agreed in many points with those of other disease-model animals promoting hearing impairment, reported to date (spontaneously hypertensive rats, spontaneously diabetic mice (KK mice), non-obese diabetic mice).
These results show that inner ear damage due to hyperlipidemia is definite.
