[Superoxide dismutase (SOD) activity measured by ESR-spin trapping method in canine vocal cords].

Recently, superoxide dismutase (SOD) has been regarded as a scavenger of superoxide radical which is a important factor of 'reperfusion injury' in ischemic heart or in brain disorder. Its low activity means cell susceptibility to the superoxide radical in tissues. The SOD activity was examined in ten canine larynges after phonation by a electron spin resonance (ESR)-spin-trapping method. The values of mean SOD activity at the middle part of the membranous vocal cord, the vocal process of the arytenoid and the subglottal portion were 67.84 +/- 11.06 U/ml/g, 121.94 +/- 19.46U/ml/g and 115.46 +/- 19.18U/ml/g, respectively. There was a significant difference between the value of the membranous vocal cord and those of the other two (P less than 0.01). The result suggests that the low SOD activity at the part of the membranous vocal cord might relate to a pathogenesis of the laryngeal polyp and vocal nodule. The reperfusion injury may participate in the cause of such vocal cord disorders which grow commonly at the middle part of the membranous vocal cord.