OBJECTIVETo investigate uptake and accumulation of gentamicin by cells in the guinea pig inner ear after intratympanic injection using a fluorescent probe--gentamicin-Texas-red conjunction (GTTR).

METHODSAdult guinea pigs (n = 80) were administered a single dose of GTrR to the middle ear cavity through the intact membrane and survived for 12 h, 24 h, 48 h, 3 d, 4 d, 7 d, 14 d and 28 d. The distribution of GTTR in the cochlear and vestibular cells was observed after staining with phalloidin-alexa-488. Texas Red and DMSO were injected into the tympanum as control.

RESULTSDiffuse staining of gentamicin in the labyrinth was observed initially after local drug administration. At later time point the outer hair cells and sensory cells of vestibular organ were staining more densely than the support cells in the inner ear. The peak level of fluorescent density was reached 3 days after local injection. The GTTR was observed in the infracuticular zone.

CONCLUSIONSGTTR was a potential fluorescent probe to investigate the pharmacokinetics and mechanisms of gentamicin accumulation in local application.