Gentamicin alters nitric oxide production in semicircular canals and otolith organs.

Objectives/hypothesis: Intratympanic application of gentamicin is an important therapeutic option to control vertigo spells in Ménière's disease. Low doses eliminate the function of semicircular canal ampullae (SCCA) and saccule in most patients, although utricular function is maintained in many cases. Local alteration in free radical production might be responsible for these differences. Therefore, the gentamicin-induced nitric oxide (NO) production was determined in an animal model using separate organ cultures of SCCA, saccule, and utricle.

Study Design: Prospective pilot study in male guinea pigs.

Methods: SCCA, saccule, and utricle of 28 guinea pigs were isolated and incubated separately for 6 hours in cell culture medium. Gentamicin was administered in two different concentrations (0.4 mg/mL and 0.8 mg/mL) to organ cultures of 16 animals. Tissues from 12 animals were used as controls. Nitric oxide was quantified by chemiluminescence.

Results: Gentamicin led to an NO increase of about 70% in the saccule, an NO reduction of more than 70% in SCCA, and an NO reduction of 36% in the utricle.

Conclusions: The selective effects of gentamicin on the NO production in the different sensory areas of the vestibular organ have to be taken into account in the therapy of Ménière's disease.