Chan H C, Liu C Q, Fong S K, Law S H, Wu L J, So E, Chung Y W, Ko W H, Wong P Y
Department of Physiology, Faculty of Medicine, Chinese University of Hong Kong, Shatin, Hong Kong.
J Membr Biol. 1997 Mar 1;156(1):45-52. doi: 10.1007/s002329900186.
The present study explored regulation of electrogenic ion transport across cultured mouse endometrial epithelium by extracellular ATP using the short-circuit current (ISC) and the patch-clamp techniques. The cultured endometrial monolayers responded to apical application of ATP with an increase in ISC in a concentration-dependent manner (EC50 at 3 microM). Replacement of Cl- in the bathing solution or treatment of the cells with Cl- channel blockers, DIDS and DPC, markedly reduced the ISC, indicating that a substantial portion of the ATP-activated ISC was Cl(-)-dependent. Amiloride at a concentration (10 microM) known to block Na+ channels was found to have no effect on the ATP-activated ISC excluding the involvement of Na+ absorption. Adenosine was found to have little effect on the ISC excluding the involvement of P1 receptors. The effect of UTP, a potent P2U receptor agonist on the ISC was similar to that of ATP while potent P2X agonist, alpha-beta-Methylene adenosine 5'-triphosphate (alpha-beta-M-ATP) and P2Y agonist, 2-methylthio-adenosine triphosphate (2-M-ATP), were found to be ineffective. The effect of ATP on ISC was mimicked by the Ca2+ ionophore, ionomycin, indicating a role of intracellular Ca2+ in mediating the ATP response. Confocal microscopic study also demonstrated a rise in intracellular Ca2+ upon stimulation by extracellular ATP. In voltage-clamped endometrial epithelial cells, ATP elicited a whole-cell Cl- current which exhibited outward rectification and delayed activation and inactivation at depolarizing and hyperpolarizing voltages, respectively. The results of the present study demonstrate the presence of a regulatory mechanism involving extracellular ATP and P2U purinoceptors for endometrial Cl- secretion.
本研究采用短路电流（ISC）和膜片钳技术，探讨了细胞外ATP对培养的小鼠子宫内膜上皮细胞电生性离子转运的调节作用。培养的子宫内膜单层细胞对顶端施加的ATP产生反应，ISC以浓度依赖的方式增加（EC50为3 microM）。用Cl-通道阻滞剂DIDS和DPC替代浴液中的Cl-或处理细胞，可显著降低ISC，这表明ATP激活的ISC的很大一部分是Cl-依赖性的。已知浓度为10 microM的氨氯地平可阻断Na+通道，但对ATP激活的ISC无影响，排除了Na+吸收的参与。发现腺苷对ISC几乎没有影响，排除了P1受体的参与。强效P2U受体激动剂UTP对ISC的作用与ATP相似，而强效P2X激动剂α-β-亚甲基腺苷5'-三磷酸（α-β-M-ATP）和P2Y激动剂2-甲硫基腺苷三磷酸（2-M-ATP）无效。Ca2+离子载体离子霉素模拟了ATP对ISC的作用，表明细胞内Ca2+在介导ATP反应中起作用。共聚焦显微镜研究还表明，细胞外ATP刺激后细胞内Ca2+升高。在电压钳制的子宫内膜上皮细胞中，ATP引发了全细胞Cl-电流，该电流在去极化和超极化电压下分别表现出外向整流以及延迟激活和失活。本研究结果表明，存在一种涉及细胞外ATP和P2U嘌呤受体的子宫内膜Cl-分泌调节机制。
