© 1989 Oxford University Press
research-article |
Effects of Acute Lead Acetate Exposure on Adult Guinea Pigs: Electrophysiological Study of the Inner Ear
*Department of Hygiene, Asahikawa Medical College, 3-11, 4-5 Nishikagura, Asahikawa, Japan
Departrnent of Public Health, Sapporo Medical College Sapporo, Japan
Received October 14, 1988; accepted April 19, 1989
The effects on humans of lead acetate exposure may involve the cranial nerves, since vertigo and sensory neuronal deafness have been reported in lead workers; however, there exist only a few reports concerning the dose effects of lead acetate both on the cochlea and the eighth cranial nerve. The effects of lead acetate on the cochlea and the eighth nerve were investigated systematically using cochlear microphonics (CM), wholenerve action potential (AP), and endocochlear potential (EP) in guinea pigs (male albino Hartley). Guinea pigs were injected with 2 ml of a 1% solution of lead acetate (20 mg) once a week for 1–5 weeks. The threshold of whole-nerve AP (N1) was elevated by injection of lead acetate, even 40 mg, and whole-nerve AP (N1) output voltage decreased after injection of 100mg of lead acetate. On the other hand, no change was observed in CM after lead acetate injection (100 mg) or in EP after lead acetate exposure (40 mg). The blood concentrations of lead acetate were as follows (mean): control, 4.5 µg/dl; Expt 1, 80 µg/dl; Expt 2, 126 µg/dl; Expt 3, 142 µg/dl;. We conclude that dysfunction of the eighth nerve is induced by high-dose lead exposure, but that lead exposure does not induce electrophysiological dysfunction of the organ of Corti and the stria vascularis.