Gentamicin ototoxicity in otoconia: quantitative electron probe X-ray microanalysis.
Chronic gentamicin ototoxicity was evaluated in the otolithic membrane of adult OF1 mice at the otoconial layer of the saccule and utricle by quantitative electron probe X-ray microanalysis of Ca and K. The otolithic membranes were plunge-frozen and freeze-dried. The analysis was carried out with an energy dispersive detector using the peak-to-back-ground ratio method and different inorganic salts of Ca and K as standards to calibrate the microprobe. Ca and K in the otoconia are related via a linear function in both the saccule and the utricle. This association is not maintained after exposure to gentamicin, which suggests that this aminoglycoside antibiotic interferes with the Ca-K equilibrium in the otoconia. A dose of 200 mg/kg gentamicin twice a day for 5 days did not affect Ca in the mineral phase of the otoconia, but did increase K in both saccular (p < 0.05) and utricular (p < 0.01) otoconia. These increases in K may reflect a modification in the composition of the endolymph, resulting from cellular damage at the plasma membrane.
Campos
A
A
Department of Histology and Cell Biology, Faculty of Medicine, University of Granada, Spain.
López-Escámez
J A
JA
Crespo
P V
PV
Cañizares
F J
FJ
Baeyens
J M
JM
D000818:Animals; D002118:Calcium / Q000032:analysis*; D003051:Cochlea / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004577:Electron Probe Microanalysis; D005839:Gentamicins / Q000008:administration & dosage / Q000633:toxicity*; D051379:Mice; D008855:Microscopy, Electron, Scanning; D010037:Otolithic Membrane / Q000737:chemistry* / Q000187:drug effects* / Q000648:ultrastructure; D011188:Potassium / Q000032:analysis*; D012444:Saccule and Utricle / Q000737:chemistry* / Q000187:drug effects* / Q000648:ultrastructure
D005839:Gentamicins; D011188:Potassium; D002118:Calcium