Isoflavones are a group of natural phytoestrogens including the compound genistein. Health beneficial effects have been attributed to the consumption of this compound, but the fact that it has estrogen-like activity has raised doubts regarding its potential risk in infants, newborns, or in the fetus and placenta during pregnancy. This work is aimed at studying genistein effects on Ca²⁺ handling by smooth muscle cells of the human umbilical artery (HUA). Using fluorometric techniques, we found that in these cells genistein reduces the intracellular Ca²⁺ peak produced by serotonin. The same result could be demonstrated in absence of extracellular Ca²⁺, suggesting that the isoflavone reduces Ca²⁺ release from the sarcoplasmic reticulum. Force measurement experiments strengthen these results, since genistein reduced the peak force attained by intact HUA rings stimulated by serotonin in a Ca²⁺-free solution. Moreover, genistein induced the relaxation of HUA rings precontracted either with serotonin or a depolarizing high-extracellular K⁺ solution, hinting at a reduction of extracellular Ca²⁺ entry to the cell. This was confirmed by whole-cell patch-clamp experiments where it was shown that the isoflavone inhibits ionic currents through voltage-operated Ca²⁺ channels. In summary, we show that genistein inhibits two mechanisms that could increase intracellular Ca²⁺ in human umbilical smooth muscle cells, behaving in this way as a potential vasorelaxing substance of fetal vessels. Taking into account that genistein is able to cross the placental barrier, these data show that isoflavones may have important implications in the regulation of feto-maternal blood flow in pregnant women who consume soy-derived products as part of their meals.

中文翻译：

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染料木黄酮对人脐动脉 Ca2+ 处理的影响：抑制肌质网 Ca2+ 释放和电压控制的 Ca2+ 通道。

异黄酮是一组天然植物雌激素，包括复合染料木黄酮。食用这种化合物对健康有益，但它具有雌激素样活性的事实令人怀疑其对婴儿、新生儿或怀孕期间胎儿和胎盘的潜在风险。这项工作旨在研究金雀异黄素对人脐动脉 (HUA) 平滑肌细胞对 Ca ²⁺处理的影响。使用荧光技术，我们发现在这些细胞中染料木黄酮降低了由血清素产生的细胞内 Ca ²⁺峰。在没有细胞外 Ca ^{2+ 的}情况下可以证明相同的结果，表明异黄酮减少了 Ca ²⁺从肌浆网释放。力测量实验加强了这些结果，因为染料木黄酮降低了由不含 Ca ^{2+ 的}溶液中的血清素刺激的完整 HUA 环所获得的峰值力。此外，染料木黄酮诱导用血清素或去极化高细胞外 K ⁺溶液预收缩的 HUA 环的松弛，暗示细胞外 Ca ²⁺进入细胞的减少。全细胞膜片钳实验证实了这一点，其中显示异黄酮通过电压控制的 Ca ²⁺通道抑制离子电流。总之，我们表明染料木黄酮抑制两种可能增加细胞内 Ca ^{2+ 的}机制在人脐带平滑肌细胞中，以这种方式作为胎儿血管的潜在血管舒张物质。考虑到染料木黄酮能够穿过胎盘屏障，这些数据表明，异黄酮可能对食用大豆衍生产品作为膳食的一部分的孕妇的胎儿-母体血流调节具有重要意义。