Quantitative analysis of free radicals in cochlea

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1. To investigate the role of free radicals in the cochlea, the concentrations of phosphatidylcholine(PC) and phosphatidylethanolamine(PE) in the liver, perilymph of the scala tympani(PST) and the stria vascularis were measured by high-performance liquid chromatography with an electrochemical detector. PC and PE were measurable in the liver of guinea pig, though they were not detectable in PST or the stria vascularis. The methods for sampling of cochlear tissues should be altered as the freezed and dry materials instead of fresh samples.2. The metallic elements, such as molybdenum, copper(Cu), iron(Fe), zinc(Zn) and manganese have been reported to play important roles with respect to free radicals in many tissues including central nervous system. In the present study, phosphorus and eight metallic elements, i.e.calcium, Cu, Fe, potassium, magnesium(Mg), sodium, lead and Zn were measurable in a single sample (2mul) of PST using a new methods, an inductively-coupled plasma atomic emission spectrometry.There was no significant effect of acoustic overstimulation on the concentrations of these elements except for Mg, which decreased significantly after the exposure to an intense sound (2 kHz, 115 dB SPL) for 15 min. The concentrations of these metallic elements were not affected by the asphxia for 3 min. After the anoxia, there was no significant change in the contents of these elements except for Fe, which increased significantly at 5 min after restoration of the artificial ventilation and decreased rapidly thereafter to the level at steady state in 15 min.