Ezimokhai M, Aloamaka C P, Cherian T, Morrison J
Department of Obstetrics and Gynaecology, Faculty of Medicine and Health Sciences, UAE University, Al Ain.
J Comp Physiol B. 1994;164(1):81-7. doi: 10.1007/BF00714575.
The effect of pregnancy on the supply of calcium ions for the contractile responses of rat aortic rings to phenylephrine was investigated. The contractility of intact aortic rings from pregnant rats, compared with that of similar rings from non-pregnant rats, to phenylephrine and potassium chloride was significantly decreased. Contractions of rings from non-pregnant rats, pretreated with phenylephrine or potassium chloride, in response to calcium chloride were greater than those of similarly treated rings from pregnant rats. When the concentration of calcium chloride in the medium bathing the rings was reduced to 0.8 mmol.l-1, the contractile response to phenylephrine was significantly (P < 0.005) inhibited in rings from both pregnant and non-pregnant rats but to a greater extent in rings from non-pregnant rats. Contractions of aortic rings from pregnant rats in response to phenylephrine in calcium-free medium were similar to those of rings from non-pregnant rats, suggesting equal dependence on calcium from intracellular stores. The results suggest that pregnancy decreased the response to calcium influx into the aortic smooth muscle cells through both receptor- and voltage-operated calcium entry pathways. Since de-endothelialization reversed the pregnancy-induced diminished contraction to phenylephrine, it is likely that pregnancy interfered with contractions induced by activation of receptors with phenylephrine through enhanced production of endothelium-derived relaxing factor(s).
研究了妊娠对大鼠主动脉环对去氧肾上腺素收缩反应中钙离子供应的影响。与未孕大鼠的类似主动脉环相比，孕鼠完整主动脉环对去氧肾上腺素和氯化钾的收缩性显著降低。用去氧肾上腺素或氯化钾预处理的未孕大鼠主动脉环对氯化钙的收缩反应大于孕鼠经类似处理的主动脉环。当环浴液中氯化钙浓度降至0.8 mmol·l-1时，孕鼠和未孕大鼠主动脉环对去氧肾上腺素的收缩反应均显著（P<0.005）受到抑制，但未孕大鼠主动脉环的抑制程度更大。无钙培养基中孕鼠主动脉环对去氧肾上腺素的收缩反应与未孕大鼠主动脉环相似，表明对细胞内钙库的钙依赖性相同。结果表明，妊娠通过受体介导和电压门控钙内流途径降低了主动脉平滑肌细胞对钙内流的反应。由于去内皮化逆转了妊娠引起的对去氧肾上腺素收缩减弱的现象，因此妊娠很可能通过增强内皮衍生舒张因子的产生，干扰了去氧肾上腺素激活受体所诱导的收缩。
