Borisenko G G, Osipov A N, Kazarinov K D
Department of Biophysics, Russian State Medical University, Moscow, Russia.
Biochemistry (Mosc). 1997 Jun;62(6):661-6.
Relaxation of blood vessel walls is one of the physiological effects induced by visible radiation. This effect is similar to the endothelium-derived relaxation (based on endothelium-derived relaxing factor, EDRF) and depends on the presence of nitric oxide donors. We assumed that nitric oxide hemoglobin (HbNO) might participate in the mechanism of this phenomenon and investigated the photochemical reactions using low-power He-Cd (441.6 nm) and He-Ne (632.8 nm) lasers. It was found that in the presence of oxygen the He-Cd laser but not He-Ne laser induced a photolytic decrease of the HbNO EPR signal amplitude by 25-35%. Using optical absorption measurements, we showed that methemoglobin was formed during irradiation. The comparison of the kinetics of this process and the irreversible reduction of paramagnetic centers suggest that the laser radiation leads to dissociation of the heme-NO complexes, but not to oxidation of the heme iron. In the absence of oxygen the photodissociation effect did not exceed 5-10% and was reversible. We suppose that this finding can be explained by fast reassociation of NO with unligated Hb. The EPR spectrum of iminonitroxide was observed upon irradiation of HbNo with nitronyl nitroxide in a vacuum, suggesting the formation of free NO. Thus, our experiments confirm that NO-hemoglobin can reversibly dissociate and release free NO during exposure to He-Cd laser radiation.
血管壁舒张是可见光辐射诱导的生理效应之一。这种效应类似于内皮源性舒张（基于内皮源性舒张因子，EDRF），并且依赖于一氧化氮供体的存在。我们假设一氧化氮血红蛋白（HbNO）可能参与了这一现象的机制，并使用低功率氦镉（441.6 nm）和氦氖（632.8 nm）激光研究了光化学反应。结果发现，在有氧存在的情况下，氦镉激光而非氦氖激光会使HbNO的电子顺磁共振（EPR）信号幅度发生光解降低25% - 35%。通过光吸收测量，我们表明在照射过程中形成了高铁血红蛋白。对该过程动力学与顺磁中心不可逆还原的比较表明，激光辐射导致血红素 - NO复合物解离，但不会导致血红素铁氧化。在无氧情况下，光解离效应不超过5% - 10%且是可逆的。我们推测这一发现可以通过NO与未结合的Hb快速重新结合来解释。在真空中用硝酰基氮氧化物照射HbNo时观察到亚氨基氮氧化物的EPR谱，表明形成了游离NO。因此，我们的实验证实了在暴露于氦镉激光辐射期间，NO - 血红蛋白可以可逆地解离并释放游离NO。
