LOCALIZATION AND KINETICS OF 2 AMINOGLYCO SIDE ANTIBIOTICS WITH DIFFERENTIAL TOXICITIES - GENTAMICIN AND AMIKACIN IN THE SENSORY CELLS OF THE INTERNAL EAR

In order to determine the relation between uptake of aminoglycoside an tibiotic (AA) molecules by sensory cells of the inner ear and their ot otoxicity, we studied the kinetics in cochlear and in vestibular cells of two AAs: gentamicin (GM)(both cochleo- and vestibulo-toxic) and am ikacin (AK)(mainly cochleo-toxic). Guinea pigs were treated during six days with one daily injection of GM (60 mg/kg/day) or AK (450 mg/kg/d ay). AAs were detected in isolated cells using immunocytochemical tech nique with scanning laser confocal microscopy. Results demonstrate a r apid uptake and a very slow clearance of both AAs from cochlear and ve stibular hair cells. Particularly GM and AK are detected in type I and type II hair cells of the utricles and cristae ampullaris. The presen ce of these two molecules with different toxic potentialities towards the cochlea or the vestibule in cochlear as well as in vestibular hair cells indicate that the selective toxicity of aminoglycosides cannot be explained solely on the basis of particular uptake and accumulation in the different sensorineural receptors.