Parry T E, Laurence A S, Blackmore J A, Roberts B
Clin Lab Haematol. 1985;7(4):317-26. doi: 10.1111/j.1365-2257.1985.tb00046.x.
Serum methionine and valine have been assayed microbiologically in 31 patients anaesthetized with and in 13 controls anaesthetized without nitrous oxide. Isoleucine has been similarly assayed in five cases and three controls. The preinduction levels of both methionine and valine were considerably below those of semifasting healthy adults. Serum methionine fell significantly in both groups as did valine and isoleucine in the controls. These findings are attributed to dietary restriction before and during the operation. Serum valine was significantly elevated in patients anaesthetized with nitrous oxide but only in those anaesthetized for 3 h or longer. Isoleucine also was elevated in two of the five cases exposed to nitrous oxide. Reasons are given for attributing these elevated levels to the direct action of nitrous oxide. Valine is entirely and isoleucine is partly catabolized along the adenosylcobalamin dependent propionyl-CoA-succinyl-CoA pathway. It is concluded that their elevated levels are caused by the inactivation of adenosylcobalamin by nitrous oxide thereby inducing the methylmalonyl mutase block in this pathway. It is suggested also that the relief of this block by adenosylcobalamin in pernicious anaemia could provide a possible metabolic basis for the well recognized early subjective improvement encountered in this disease following vitamin B12 therapy.
已对31例接受笑气麻醉的患者和13例未接受笑气麻醉的对照者进行了血清蛋氨酸和缬氨酸的微生物学测定。对5例患者和3例对照者进行了异亮氨酸的类似测定。诱导前蛋氨酸和缬氨酸的水平均明显低于半饥饿健康成年人。两组患者血清蛋氨酸均显著下降，对照组的缬氨酸和异亮氨酸也显著下降。这些发现归因于手术前和手术期间的饮食限制。接受笑气麻醉的患者血清缬氨酸显著升高，但仅在麻醉3小时或更长时间的患者中出现。在接受笑气的5例患者中有2例异亮氨酸也升高。给出了将这些升高水平归因于笑气直接作用的原因。缬氨酸完全通过依赖腺苷钴胺素的丙酰辅酶A-琥珀酰辅酶A途径分解代谢，异亮氨酸部分通过该途径分解代谢。得出的结论是，它们的升高水平是由笑气使腺苷钴胺素失活从而在该途径中诱导甲基丙二酸变位酶阻滞所致。还提出，在恶性贫血中腺苷钴胺素缓解这种阻滞可能为维生素B12治疗后该病早期公认的主观改善提供一种可能的代谢基础。
