[Glutamate induced modulation of free Ca2+ in isolated inner hair cells of the guinea pig cochlea].
OBJECTIVE
To investigate the modulation effect of glutamate (Glu) on intracellular free Ca2+ concentration([Ca2+]i) of inner hair cell (IHC).


METHODS
Using the laser scanning confocal microscope (LSCM), the exogenous Glu-induced changes in [Ca2+]i of isolated 10 IHCs and 10 OHCs of guinea pig cochlea were observed with fluo-3, a fluorescent probe for [Ca2+]i.


RESULTS
The IHCs were identified by their unique flask shape with a distinct neck and spherical base and a large spherical nucleus. In most cases, normal cell shapes could be maintained about two hours after isolation. The images of [Ca2+]i from LSCM were similar to those from inverted microscopy. Fluorescence of Fluo-3 distributed in the isolated IHCs with brighter staining in the nucleus. In the presence of low concentration of Glu (3.85 mumol/L), there was an increase of [Ca2+]i in IHCs, whereas no change in OHCs was found. Of the 10 IHCs, increases of [Ca2+]i were observed in 9 and no change in 1. Of the 10 OHCs, 7 showed no [Ca2+]i change and only 3 showed minor reduction of [Ca2+]i. An increase of the Glu concentration (21.88 mumol/L) induced a corresponding increase of [Ca2+]i in IHCs, but eventually resulted in a gradual decrease of [Ca2+]i with a distortion of the normal shape, which indicated that the IHCs were degenerated and swelling.


CONCLUSIONS
These results suggested that exogenous Glu is capable of modulating [Ca2+]i of IHC and may be act on autoreceptor in a positive feedback manner. Excessive Glu induced the accumulation of IHC [Ca2+]i which finally resulted in the degeneration and edema of IHC and the reduction of IHC [Ca2+]i.
Li
X
X
Department of Otorhinolaryngology, Chinese PLA General Hospital, Beijing 100853, China. lixq@plagh.com.cn
Sun
J
J
Yu
N
N
Sun
Y
Y
Tan
Z
Z
Jiang
S
S
Li
N
N
Zhou
C
C
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D003051:Cochlea / Q000166:cytology* / Q000378:metabolism; D005260:Female; D018698:Glutamic Acid / Q000494:pharmacology*; D006168:Guinea Pigs; D006199:Hair Cells, Auditory, Inner / Q000187:drug effects* / Q000378:metabolism; D066298:In Vitro Techniques; D017136:Ion Transport / Q000187:drug effects; D008297:Male
D018698:Glutamic Acid; D002118:Calcium