一酸化窒素ヘモグロビンと酸素との反応の解析
メトヘモグロビン生成とヘモグロビンの変質
1980 年 15 巻 10 号 p. 401-411
詳細
1980 年 15 巻 10 号 p. 401-411
Nitros-ylhemoglobin (Hb-NO), prepared in a gas-tight syringe anaerobically, was reacted with dissolved oxygen (O2) in phosphate buffered saline at pH 7.4 and 37°C. The reaction process was monitored by measuring (i) O2 concentration in the medium by O2 electrode, continuously, (ii) Hb-NO and methemoglobin (Met Hb) concentrations by EPR spectroscopy and (iii) NO2- and NO3- concentrations by chemical analyses.
(1) Hb-NO was quantitatively converted to Met Hb by consuming dissolved O2, and NO3- was produced.The reaction process consisted of branched, successive reactions:(i) The dissociation of Hb-NO was rate-limiting step, yielding deoxyhemoglobin (deoxy Hb) and NO; NO in solution changed to NO2-.(ii) At higher O2concentration, oxyhemoglobin (Hb-O2) was transiently formed, and reacted with NO2-, yielding Met Hb and NO3-.(iii) At lower O2 concentration, deoxy Hb reacted with NO2-. yielding Hb-NO, Met Hb and NO3-.(iv) NO3- production from NO2- and O2 was catalyzed by Met Hb. The following scheme was proposed.
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(2) As proceeding the Met Hb formation from Hb-NO, the ratio of α-NO to β-NO in Hb-NO augumented and the alteration of α-NO was found, as judged from ESR spectra.
(3) The reaction between Hb-NO in erythrocytes and dissolved O2 was qualitatively interpreted by the proposed scheme.
