Ekholm S E, Reece K, Foley M, Kido D K, Morris T
Invest Radiol. 1984 Nov-Dec;19(6):574-7. doi: 10.1097/00004424-198411000-00019.
In a previous in vitro study we demonstrated reduced CO2 production in rat hippocampal tissue when metrizamide was added. This metabolic depression is believed to be a result of the 2-deoxy-D-glucose (2-DG) portion of the metrizamide molecule since 2-DG is a known competitive inhibitor of glucose metabolism. This competitive inhibition probably occurs at the cell membrane since it has never been shown that metrizamide penetrates neural cells. Further the inhibition is most likely related to competition for the membrane glucose carrier. A new nonionic contrast medium, iohexol, does not contain a 2-DG component and if the hypothesis for the metabolic inhibition is valid we should not expect metabolic inhibition with iohexol. This hypothesis was tested using the rat hippocampus model previously used for metrizamide. We compared iohexol with metrizamide in isotonic concentrations and also examined the effect of hypertonicity. These experiments did not demonstrate inhibition of CO2 production with iohexol at near physiologic osmolalities, however, there was a marked depressive effect with increasing osmolality. This effect from hypertonicity is, however, probably of less importance in vivo where water will rapidly diffuse toward the hypertonic areas. The apparent lack of interference of the iohexol molecule on glucose metabolism should therefore make iohexol a more suitable contrast medium, for subarachnoid investigations than metrizamide.
在之前的一项体外研究中，我们发现加入甲泛葡胺后大鼠海马组织中的二氧化碳生成减少。这种代谢抑制被认为是甲泛葡胺分子中2-脱氧-D-葡萄糖（2-DG）部分的结果，因为2-DG是一种已知的葡萄糖代谢竞争性抑制剂。这种竞争性抑制可能发生在细胞膜上，因为从未有研究表明甲泛葡胺能穿透神经细胞。此外，这种抑制很可能与对膜葡萄糖载体的竞争有关。一种新的非离子型造影剂碘海醇不含有2-DG成分，如果代谢抑制的假设成立，那么我们不应预期碘海醇会产生代谢抑制作用。我们使用先前用于甲泛葡胺研究的大鼠海马模型对这一假设进行了测试。我们将等渗浓度的碘海醇与甲泛葡胺进行了比较，还研究了高渗的影响。这些实验表明，在接近生理渗透压时，碘海醇不会抑制二氧化碳的生成，然而，随着渗透压的升高，会产生明显的抑制作用。不过，在体内，水会迅速向高渗区域扩散，因此高渗的这种影响可能不太重要。因此，碘海醇分子对葡萄糖代谢明显没有干扰，这使得碘海醇在蛛网膜下腔检查中比甲泛葡胺更适合作为造影剂。
