[Protective effect of indirect activator of calcium pump on noise-induced hearing loss].
OBJECTIVE
To investigate the possible protective effect of phorbol-12-myristate-13-acetate (PMA), an activator of protein kinase C (PKC) and indirect activator of Ca2+ pump, on noise-induced hearing loss (NIHL).


METHODS
Twenty guinea pigs were divided randomly into two groups, and then perfused with artificial perilymph solutions in one group and with artificial perilymph solutions containing 3 mumol/L PMA in the other one, respectively. All animals were exposed with 100 dB SPL white noise for 2 hours. Cochlear microphonics (CM) and compound action potential (CAP) were recorded from the round window (RW) before noise exposure and 2 hours after noise exposure.


RESULTS
There was no significant difference in CAP threshold and CM amplitude between two groups before noise exposure. A significant difference was observed in CAP threshold and CM amplitude between two groups after noise exposure. The amplitude of CM decreased and the threshold of CAP increased in both group after noise exposure, but in the PMA group the decrease of the amplitude of CM was higher while the increase of threshold of CAP lower than that in control (P < 0.05).


CONCLUSIONS
PMA might have partly protective effect on NIHL. These findings indirectly proved that intracellular Ca2+ overload might involve in the mechanism of NIHL.
Liu
Jun
J
Department of Otorhinolaryngology Head and Neck Surgery, PLA General Hospital, Beijing 100853, China.
Yu
Ning
N
Han
Dongyi
D
Yang
Weiyan
W
Li
Xingqi
X
D000200:Action Potentials; D000818:Animals; D002120:Calcium Channel Agonists / Q000494:pharmacology*; D003055:Cochlear Microphonic Potentials; D005260:Female; D006168:Guinea Pigs; D006317:Hearing Loss, Noise-Induced / Q000517:prevention & control*; D008297:Male; D011897:Random Allocation; D013755:Tetradecanoylphorbol Acetate / Q000031:analogs & derivatives* / Q000494:pharmacology*
D002120:Calcium Channel Agonists; C016658:phorbolol myristate acetate; D013755:Tetradecanoylphorbol Acetate