Danielsson Bengt R, Johansson Alf, Danielsson Christian, Azarbayjani Faranak, Blomgren Bo, Sköld Anna-Carin
Department of Pharmaceutical Biosciences, Division of Toxicology, Uppsala University, S-751 24 Uppsala, Sweden.
Birth Defects Res A Clin Mol Teratol. 2005 Mar;73(3):146-53. doi: 10.1002/bdra.20124.
The antiepileptic drug phenytoin (PHT) is a human and animal teratogen. The teratogenicity has been linked to PHT-induced embryonic cardiac arrhythmia and hypoxic damage during a period when regulation of embryonic heart rhythm is highly dependent on a specific K(+) ion current (I(Kr)). PHT has been shown to inhibit I(Kr). The aims of this study were to investigate whether teratogenic doses cause embryonic hypoxia during and after the I(Kr) susceptible period and to further characterize PHT effects on embryonic heart rhythm.
Pregnant C57BL mice were administered the hypoxia marker pimonidazole followed by PHT or saline (controls) on GD 10 or GD 15. The embryos were fixed and sectioned, and the immunostained sections were analyzed with a computer assisted image analysis. Effects of PHT (0-250 microM) on heart rhythm in GD 10 embryos cultured in vitro were videotaped and then analyzed by using a digitalization technique.
PHT dose-dependently increased the hypoxia staining (6- and 11-fold after maternal dosing of 100 and 150 mg/kg, respectively) during the period I(Kr) is expressed and functional (GD 10). In contrast, there were no differences between the PHT doses in hypoxia staining, and much less pronounced hypoxia after this period (GD 15). With increasing PHT concentrations, increased length of the interval (bradycardia) and large variations in length between individual heartbeats (arrhythmia) were recorded.
PHT induced bradycardia/arrhythmia and severe embryonic hypoxia during the I(Kr) susceptible period, supporting the idea of an I(Kr)-arrhythmia-hypoxia-related teratogenic mechanism.
抗癫痫药物苯妥英（PHT）是一种对人类和动物具有致畸性的药物。这种致畸性与PHT诱导的胚胎心律失常以及在胚胎心律调节高度依赖特定钾离子电流（I(Kr)）的时期所产生的缺氧损伤有关。已有研究表明PHT可抑制I(Kr)。本研究的目的是调查致畸剂量的PHT在I(Kr)易感期及之后是否会导致胚胎缺氧，并进一步明确PHT对胚胎心律的影响。
在妊娠第10天（GD 10）或第15天（GD 15），给怀孕的C57BL小鼠注射缺氧标记物匹莫硝唑，随后给予PHT或生理盐水（作为对照）。将胚胎固定、切片，对免疫染色的切片进行计算机辅助图像分析。用录像记录PHT（0 - 250微摩尔）对体外培养的GD 10胚胎心律的影响，然后采用数字化技术进行分析。
在I(Kr)表达且发挥功能的时期（GD 10），PHT剂量依赖性地增加了缺氧染色（母体给药100毫克/千克和150毫克/千克后分别增加6倍和11倍）。相比之下，在此时期之后（GD 15），不同PHT剂量组的缺氧染色没有差异，且缺氧程度明显减轻。随着PHT浓度增加，记录到间期延长（心动过缓）以及个体心跳之间长度的大幅变化（心律失常）。
PHT在I(Kr)易感期诱导心动过缓/心律失常以及严重的胚胎缺氧，支持了I(Kr) - 心律失常 - 缺氧相关致畸机制的观点。
