Nakai K, Ohta T, Sakuma I, Akama K, Kobayashi Y, Tokuyama S, Kitabatake A, Nakazato Y, Takahashi T A, Sadayoshi S
Department of Cell Processing, Institute of Medical Science, University of Tokyo, Japan.
J Cardiovasc Pharmacol. 1996 Jul;28(1):115-23. doi: 10.1097/00005344-199607000-00018.
Hemoglobin (Hb)-based artificial oxygen carriers are supposed to induce vasoconstriction through the inactivation of endothelium-derived relaxing factor (EDRF). We examined the vasoconstrictive activity of acellular Hb and cellular Hb solutions in rabbit aortic strips. Unmodified Hb, pyridoxalated Hb, bovine unmodified Hb, haptoglobin-Hb complex (Hp-Hb), and polyoxyethylene glycol-conjugated Hb (PEG-Hb) were used as acellular Hbs having different molecular masses. Cellular Hbs included liposome-encapsulated Hb and red blood cells (RBC). In the first experiment, Hb (10 ng/ml to 1 mg/ml) was cumulatively added to the tissues in which steady-state relaxation was evoked by acetylcholine (ACh) after precontraction induced by phenylephrine. Although all Hb solutions induced a dose-dependent reversal of ACh-induced relaxation, the most potent vasoconstrictive effect was noted with acellular Hbs, and their contractile activities were almost the same independent of molecular mass. On the other hand, liposome-Hb and RBC showed reduced potencies in this order. These results indicate the importance of cellularity as the major factor determining Hb-related EDRF inactivation. In another experiment, the tissues were exposed to Hb at 0.01, 0.1, or 1 mg/ml for 30 min and ACh-induced relaxation was recorded after the complete removal of Hb in an organ bath chamber. Exposure to unmodified Hb at > 0.1-mg/ml concentrations significantly reduced the ACh-induced relaxation, whereas the relaxation was not affected by PEG-Hb, Hp-Hb, liposome-Hb, or RBC. These results suggest that unmodified Hb might be persistently associated with tissues and thereby inhibit ACh-induced relaxation. From these findings, we propose two attributes of Hb-related inhibition of endothelium-dependent relaxation: Acellular Hbs inhibit EDRF more efficiently in the luminal space than cellular Hbs, and unmodified Hb can also inhibit it adluminally and/or adventitially.
基于血红蛋白（Hb）的人工氧载体被认为可通过使内皮衍生舒张因子（EDRF）失活来诱导血管收缩。我们检测了脱细胞Hb溶液和细胞Hb溶液对兔主动脉条的血管收缩活性。未修饰的Hb、吡哆醛化Hb、牛未修饰Hb、触珠蛋白-Hb复合物（Hp-Hb）以及聚乙二醇共轭Hb（PEG-Hb）用作具有不同分子量的脱细胞Hb。细胞Hb包括脂质体包裹的Hb和红细胞（RBC）。在第一个实验中，在去氧肾上腺素引起预收缩后，将Hb（10 ng/ml至1 mg/ml）累积添加到由乙酰胆碱（ACh）引起稳态舒张的组织中。尽管所有Hb溶液均引起ACh诱导舒张的剂量依赖性逆转，但脱细胞Hb的血管收缩作用最为显著，并且它们的收缩活性几乎相同，与分子量无关。另一方面，脂质体-Hb和RBC的效力依次降低。这些结果表明细胞性作为决定与Hb相关的EDRF失活的主要因素的重要性。在另一个实验中，将组织暴露于0.01、0.1或1 mg/ml的Hb中30分钟，并在器官浴槽中完全去除Hb后记录ACh诱导的舒张。暴露于浓度> 0.1 mg/ml的未修饰Hb会显著降低ACh诱导的舒张，而PEG-Hb、Hp-Hb、脂质体-Hb或RBC则不会影响舒张。这些结果表明未修饰的Hb可能会持续与组织结合，从而抑制ACh诱导的舒张。基于这些发现，我们提出与Hb相关的内皮依赖性舒张抑制的两个特性：脱细胞Hb在管腔空间比细胞Hb更有效地抑制EDRF，并且未修饰的Hb也可以在管腔和/或外膜抑制它。
