Sartor P, Couderc B, Corcuff J B, Odessa M F, Mayer G, Dufy B
Laboratoire de Neurophysiologie, CNRS URA 1200, Bordeaux, France.
Endocrinology. 1992 Jun;130(6):3433-40. doi: 10.1210/endo.130.6.1597150.
Human decidual cells synthesize and release decidual PRL (dPRL) immunologically and biochemically identical to human pituitary PRL. However, stimulators and inhibitors of PRL secretion such as TRH, bromocriptine or dopamine have no effect on dPRL release. The evidence for the involvement of Ca2+ in dPRL release is based on contradictory or unclear data. Since little is known about Ca2+ movement in human decidual cells we studied the membrane Ca2+ conductance of cultured decidual cells using the patch-clamp technique in the whole-cell configuration. We report the existence of Ca(2+)-dependent action potentials triggered by hyperpolarizing or depolarizing pulses and blocked by cobalt (Co2+; 5 mM). Spontaneous action potentials were observed in the cell-attached mode and found also to be Co(2+)-sensitive. A tetrodotoxin-insensitive and Ca(2+)-dependent rapidly inactivating inward current was investigated in voltage clamp. Its activation threshold was between -60 and -45 mV. Indo-1 measurements of free intracellular Ca2+ concentrations ([Ca2+]i, 169 +/- 14 nM and 141 +/- 8 nM in short-term culture vs. 149 +/- 5 nM in cells cultured for 3-6 days) showed that decidual cells have spontaneous transient fluctuations of [Ca2+]i and that [Ca2+]i was decreased by Ca2+ channel blockers. The existence of Ca2+ movements in decidual cells in culture is thus demonstrated. The occurrence of action potentials in decidual cells derived from fibroblasts, reputed to be inexitable cells, is an interesting biological observation. However, Ca2+ is not involved in the short-term release of PRL by decidual cells, and its effects on long-term secretion still requires further investigation.
人蜕膜细胞合成并释放的蜕膜催乳素（dPRL）在免疫学和生物化学性质上与人类垂体催乳素相同。然而，催乳素分泌的刺激剂和抑制剂，如促甲状腺激素释放激素（TRH）、溴隐亭或多巴胺，对dPRL的释放没有影响。关于Ca2+参与dPRL释放的证据基于相互矛盾或不明确的数据。由于对人蜕膜细胞中Ca2+的移动了解甚少，我们采用全细胞膜片钳技术研究了培养的蜕膜细胞的膜Ca2+电导。我们报告了由超极化或去极化脉冲触发并被钴（Co2+；5 mM）阻断的Ca(2+)依赖性动作电位的存在。在细胞贴附模式下观察到自发动作电位，并且发现其对Co(2+)敏感。在电压钳实验中研究了一种对河豚毒素不敏感且Ca(2+)依赖性快速失活的内向电流。其激活阈值在-60至-45 mV之间。Indo-1对细胞内游离Ca2+浓度（[Ca2+]i，短期培养时为169±14 nM，培养3 - 6天的细胞中为141±8 nM，而短期培养时为149±5 nM）的测量表明，蜕膜细胞具有[Ca2+]i的自发瞬时波动，并且[Ca2+]i可被Ca2+通道阻滞剂降低。因此证明了培养的蜕膜细胞中存在Ca2+移动。源自成纤维细胞（被认为是不可兴奋细胞）的蜕膜细胞中动作电位的出现是一个有趣的生物学现象。然而，Ca2+不参与蜕膜细胞催乳素的短期释放，其对长期分泌的影响仍需进一步研究。
