Gentamicin binding to the isolated crista ampullaris of the guinea pig

Isolated cristae ampullares of the guinea pig were incubated in vitro to study the kinetics of gentamicin binding. Binding of radiolabelled gentamicin reached an equilibrium at 10 min. Three binding sites were determined: Kd = 30 microM, n = 3.2 nmoles drug/mg protein; Kd = 317 microM, n = 26 nmoles; and Kd = 965 microM, n = 52 nmoles. Gentamicin remained bound to the crista after glutaraldehyde fixation and processing for electron microscopy. It is suggested that the isolated crista ampullaris may serve as a useful model for the study of aminoglycoside kinetics as related to ototoxicity.