Department of Biomaterials, University of Ulm, Central Institute for Biomedical Engineering, Ulm, Germany.
Clin Hemorheol Microcirc. 2010;45(2-4):123-30. doi: 10.3233/CH-2010-1290.
Isoforms of the enzyme lactate dehydrogenase (LDH) were found in almost all cells of the organism and an elevated activity of LDH in the circulation is thought to be a clear indicator of elevated cell destruction coinciding with an increased release of components from the cellular cytoplasm, e.g. LDH. Here, we report on an in-vitro examination to test whether radiographic contrast media (RCM) could induce cell destruction followed by an increase in LDH release. The RCM were tested in non-flow cultures of human umbilical venous endothelial cells (HUVEC) of the fourth passage seeded on extracellular matrix and the results were compared to those from control cultures not exposed to contrast media. The examination revealed that the addition of contrast media to the cell culture media supplemented with pooled human serum (HSP) as source of exogenous LDH was followed by a strong decrease in LDH activity both in the absence and presence of HUVEC. Within 1.5 min after the addition of contrast media to the culture medium supplemented with HSP (30% vol of the culture medium were replaced by either of two contrast media, Iodixanol or Iopromide) the LDH activity decreased about 80% compared to the initial values. In contrast, the LDH activity did not change in cell culture media not supplemented with RCM. The partial replacement of HSP supplemented cell culture medium by RCM will cause a dilution of cell culture medium constituents. The decrease of LDH activity, however, was much stronger than the decrease thought to be attributable to the effects of dilution of cell culture medium, so that the role of dilution seems to be a minor one in this case. It has to be assumed that the RCM could interact with the LDH available in the culture medium as well as with the substrates delivered with the measurement system for the assessment of LDH activity, so that both, the amount of LDH and the activities of enzymes involved might be influenced. In the presence of HUVEC a similar effect was observed. Here, a little less strong decrease of LDH activity occurred compared to the decrease in cell culture medium without HUVEC. This was unexpected because a considerable amount of HUVEC were detached after the addition of contrast media and many of these cells were damaged seriously so that a significant amount of endogenous LDH should have been released. These unexpected results make it necessary to re-evaluate those past time examinations focussed on cell damage/destruction in the presence of contrast media, where the measurement of LDH activity was used as indicator or cell vitality and where cell decease rates were correlated to questionable toxic influences. According to the results of the examination reported here it is difficult to uphold the interpretation of recently published findings that contrast media almost exclusively induce cellular apoptosis and not necrosis.
酶乳酸脱氢酶（LDH）的同工型存在于机体的几乎所有细胞中，循环中 LDH 活性的升高被认为是细胞破坏增加的明确指标，这与细胞质成分的释放增加相一致，例如 LDH。在这里，我们报告了一项体外检查，以测试放射性对比剂（RCM）是否会引起细胞破坏，随后 LDH 释放增加。在第 4 代人脐静脉内皮细胞（HUVEC）的非流动培养物中测试了 RCM，将结果与未暴露于对比介质的对照培养物进行了比较。检查显示，在含有混合人血清（HSP）作为外源 LDH 来源的细胞培养基中添加对比介质后，无论是在不存在还是存在 HUVEC 的情况下，LDH 活性都强烈下降。在添加 HSP 补充的培养基（培养基中 30%体积被两种对比介质之一碘克沙醇或碘普罗胺替代）后 1.5 分钟内，与初始值相比，LDH 活性降低了约 80%。相比之下，未补充 RCM 的细胞培养基中的 LDH 活性没有变化。RCM 对 HSP 补充的细胞培养基的部分替代会导致细胞培养基成分的稀释。然而，LDH 活性的降低远强于由于细胞培养基稀释引起的降低，因此稀释的作用在这种情况下似乎较小。可以假设 RCM 可以与培养基中存在的 LDH 以及用于评估 LDH 活性的测量系统中提供的底物相互作用，因此，LDH 的量和涉及的酶的活性都可能受到影响。在存在 HUVEC 的情况下，观察到类似的效果。与没有 HUVEC 的细胞培养基相比，LDH 活性的降低稍弱。这出乎意料，因为添加对比介质后，相当数量的 HUVEC 被分离，其中许多细胞严重受损，因此应该有大量内源性 LDH 被释放。这些意外的结果使得有必要重新评估过去的时间检查，这些检查集中在存在对比介质时的细胞损伤/破坏，其中 LDH 活性的测量被用作细胞活力的指标，并且细胞死亡率与可疑的毒性影响相关。根据这里报告的检查结果，很难坚持最近发表的发现的解释，即对比介质几乎仅诱导细胞凋亡而不是坏死。
