Avioli L V, Bizzarri C, Civitelli R
Division of Bone and Mineral Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA.
Miner Electrolyte Metab. 1995;21(1-3):29-34.
Putative osteoblastic UMR 106-01 cells exhibit heterogeneous intracellular calcium [Ca2+]i responses to parathyroid hormone (PTH). To determine whether this phenomenon is secondary to cell cycle asynchrony, UMR 106-01 cultures were synchronized at the G1/S boundary using a sequential thymidine-aphidicolin treatment. Five hours after release from the block > 80% of the cells are in S phase, while nontreated confluent cultures are in G1. Using video image analysis of single cells loaded with fura-2, PTH (10-(7) M) induced transient increases in [Ca2+]i preferentially in cells in S phase, with 82% response frequency whereas cells in G1 phase responded poorly to PTH with only 10% response frequency. In contrast, cell response to fetal calf serum was more frequent in G1 than in S phase. Pretreatment with La3+, nifedipine or pertussis toxin reduced both the frequency and amplitude of the PTH response in S phase to values comparable to those observed in cells in G1 phase. There was no significant difference in inositol trisphosphate generated by PTH stimulation in either phase. Thus, the heterogeneous osteoblastic [Ca2+]i responsive to PTH is cell cycle-dependent with the change in the G1 to the S phase mode of response dependent on active coupling between the PTH receptor and a Ca2+ channel via a pertussis toxin-sensitive G protein.
假定的成骨细胞UMR 106-01细胞对甲状旁腺激素（PTH）表现出异质性的细胞内钙[Ca2+]i反应。为了确定这种现象是否继发于细胞周期不同步，使用胸腺嘧啶核苷-阿非迪霉素序贯处理使UMR 106-01培养物在G1/S边界同步化。从阻断中释放5小时后，超过80%的细胞处于S期，而未处理的汇合培养物处于G1期。使用对负载fura-2的单细胞进行视频图像分析，PTH（10-(7) M）优先在S期细胞中诱导[Ca2+]i的瞬时增加，反应频率为82%，而G1期细胞对PTH反应较差，反应频率仅为10%。相反，G1期细胞对胎牛血清的反应比S期更频繁。用La3+、硝苯地平或百日咳毒素预处理可将S期PTH反应的频率和幅度降低到与G1期细胞中观察到的值相当的水平。两个阶段中PTH刺激产生的肌醇三磷酸没有显著差异。因此，对PTH的异质性成骨细胞[Ca2+]i反应是细胞周期依赖性的，从G1期到S期反应模式的变化取决于PTH受体与Ca2+通道通过百日咳毒素敏感的G蛋白的活性偶联。
