Dynamic changes following combined treatment with gentamicin and ethacrynic acid with and without acoustic stimulation. Cellular uptake and functional correlates.
Acta Oto-Laryngologica. 1989-01-01; 108(5-6): 404-413
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1. Acta Otolaryngol. 1989 Nov-Dec;108(5-6):404-13.
Dynamic changes following combined treatment with gentamicin and ethacrynic acid
with and without acoustic stimulation. Cellular uptake and functional correlates.
Hayashida T(1), Hiel H, Dulon D, Erre JP, Guilhaume A, Aran JM.
(1)INSERM Research Unit 229, University of Bordeaux II, France.
Regional selectivity of gentamicin (GM) ototoxicity was studied in guinea pigs
(GPs) using electrophysiological, morphological, autoradiographic and
immunohistological observations following combined treatment with GM (150 mg/kg
i.m.) and ethacrynic acid (EA) (30 mg/kg i.c. or i.v., 1.5 h after GM injection).
The GPs were either continuously stimulated every 5 min with a series of 256
clicks (70 dB peSPL, 10/s) during 3 h for monitoring fast changes in VIII nerve
compound action potential (CAP) after the EA injection, and thereafter kept in
the animal quarters (background noise of 60 dB SPL) (group I), or similarly
monitored for only 10 min after the EA injection and thereafter kept in a
soundproof room (around 0 dB SPL) (group II). Whenever GM labelling was observed
it was localized only in the sensory hair cells. From 3 h after EA injection, the
GPs in group I presented threshold elevations in the high-frequency region, which
progressed to 60-80 dB at all frequencies at and after 48 h. Parallel to the
threshold pattern, GM uptake in outer hair cells (OHCs) was seen with an
increasing concentration from apex toward base from 3 to 24 h, while after 48 h
almost all OHCs were destroyed and inner hair cells (IHCs) were marked by GM. In
group II no changes in CAP thresholds were observed until more than 24 h,
although GM was detected in the hair cells from 6 h on. At this early stage, the
distribution of GM lacked a clear pattern, particularly without a clear apex-base
gradient, and GM deposits were found only around the basal body. However in both
groups, in late stage (greater than 24 h), the base-apex gradient was more
pronounced and GM was found throughout the cell body, with a marked concentration
below the cuticular plate. These results suggest that GM may penetrate hair cells
around the basal body and that activating the cells by sound potentiates both GM
uptake and its intracellular toxicity.
PMID: 2589069 [Indexed for MEDLINE]