The Effect Of Sildenafil Citrate On Auditory In Mice

Sildenafil citrate is a selective inhibitor of type5phosphosdesterase(PDE-5).Phosphodiesterase-5inhibitors, originally developed for the treatment of angiocardiopathy,are the most commonly used drugs for the treatment of erectile dysfunction(ED). However,as the drug is widely used, the more drug side effects are reporting. In2007,Most reports ofPDE-5inhibitor related sudden sensorinerual hearing loss have come from the Food andDrug Agency(FDA) in the United States. Recently,some epidemiologic studys have alsosuggested a higher risk of hearing loss with that PDE-5inhibitor high dosage use. In allcases, sildenafil accounted for over50%of cases. Incorrect use of sildenafil can lead todeafness, therefore, it is important to study of the drug side effects. For the time being,more attention is retrospective study in borne and abroad,lacking animal studieys.This topic proposed by animal experiments to explore the effct of sildenafil citrate onauditory in mice and the mechanisn of ototoxicity, estabilish a Kunming mouse model ofsidenafil citrate ototoxicity. We surmise Sildenafil citrate injure the hearing through themechanism of injured cochlea hair cells, included morphostrctue、 ion channel andelectrophysiological mechanism. Provede medical evidence and guide the clinical treatmentfor people.Objective:1. To establishment of a Kunming mouse of Sidenafil citrate induced ototoxicity byintragastric administration;2. To explore the mechanism of Sidenafil citrate ototoxicity by using the patch-clampwhole cell recording technique to observe eclectrophysiosogical functions of inner haircells.Material and Methods:1. Seven-week-old adult male Kunming mice were used.Mice were assigned randomlyinto4groups with10mice in each group, and were orally administerd daliy Sildenafilcitrate0.1mg／k,1mg／kg,10mg／kg and saline, respectively, and at the0,1,5,10,20days to repeat test the Auditory brain-stem response(ABR). The hearing loss was test with ABR.WE labeling the cochlea inner hair cells with fluorescein isothiocyanate. Analysis ofSidenafil citrate in endolymph of mice by High performance liquid chromatography(HPLC).2. Electrophysiological effect of Sidenafil ctrate in cochclear inner hair cells: dividedcontrol group and Sidenafil citrate group. Using the patch-clamp whole cell recordingtechnique to test calcium current and membrane capacitance of inner hair cells.Result:1. The ABR threshold results: normal control group ABR thtresholds have nosignificant change with20days; Sidenafil citrate groups and control group ABR thresholdshave no progressively increasing after1days(no sifnificant statistical differencesP>0.05);Sildenafil groups are increasing after5days. Sildenafil citrate groups havevarying degrees of hearing loss comared with control group,which manifest ABR thresholdmoves up, the degrees associated with dosage. FITC fluorescence results show: normalcontrol group hair cells are arranged in pperfect order, normal morphology and,no missing.The cochlea hair cells of sildenafil low dosage group injury slighter, they have normalmorphology. The cochlea hair cells of sildenafil middle doage damage relatively light,3row outer hair cells damage. The cochlea hair cells of sildenafil high doage appeardisorders,missing and the strcture incomplete. HPLC result: Sidenfil citrate can be detectedin enndolymph of cochlea after intragastric, the peak time at5.2min, between dosage. Theresult of HPLC indicating that Sidenafil can accumulate in endolymph.2. Transmembrane calcium ionic channel currents and cell membrane capacitance wererecorded by using the whole-cell patch-clamp technique, and the data were statistic byindependent samples T test. The result: the calcium current which were record is inward,and it were activation by voltage-dependent. Compared with control group, Sidenfil canreduce calcium influx(P<0．05,statistical significance), and it can reduce cell membarancapacitance increase(P<0．05,statistical significance). cell membaran capacitance concerncell secrete neurotransmitter, Sildenafil citrate induce membrane capacitance of IHC,description the drug reduced cell releases neurotransmitters. Conclusions:1. Sildenafil citrate can be absorbed into blood and acrossed blood-babyrinth barrierthen accumulated in inner ear; a dose of sildenafil citrate cause hearing damage in mice.2. Sildenafil citrate causes hair cells damage with a concentration-dependent manner.3. Sildenafil citrate reduce inward calcium current and membrane capacitance in IHC,which may be one of the otoxicity mechanisms.