Donahue H J, Fryer M J, Eriksen E F, Heath H
Division of Endocrinology, Metabolism, and Internal Medicine, Mayo Clinic, Rochester, Minnesota 55905.
J Biol Chem. 1988 Sep 25;263(27):13522-7.
While the stimulatory effect of parathyroid hormone (PTH) on osteoblast-like cell adenylate cyclase is well known, the effect of PTH on cytosolic calcium ion ([Ca2+]i) mobilization is controversial, one group finding no effect but others reporting various increases. We investigated the effects on [Ca2+]i of synthetic rat PTH fragment 1-34 (rPTH(1-34)) and two bovine PTH analogues that inhibit PTH's stimulation of adenylate cyclase (bovine 8,18Nle, 34Tyr-PTH(3-34) and 34Tyr-PTH(7-34]. [Ca2+]i was measured before, during, and after exposure to PTH analogues in perifused, attached osteoblast-like rat osteosarcoma cells (ROS 17/2.8) that had been scrape-loaded with the luminescent photoprotein aequorin. Resting [Ca2+]i was 0.094 +/- 0.056 microM (mean +/- S.D., n = 103) and rose in a time- and dose-specific way after exposure to rPTH(1-34). At 10(-10) M rPTH(1-34), [Ca2+]i rose 100% within 30 s to a plateau; higher concentrations of PTH yielded increasing initial peaks of [Ca2+]i followed by lower plateaus. At 10(-6) M, the initial peak was 5-fold basal, or 0.64 +/- 0.07 microM. Both analogues of PTH were at least partial agonists for [Ca2+]i mobilization and did not reduce peak [Ca2+]i when co-perifused with rPTH(1-34). However, the analogues did reduce significantly rPTH(1-34)-induced cAMP accumulation and did not increase cAMP accumulation by themselves. Thus, rPTH(1-34) strongly mobilizes [Ca2+]i in ROS 17/2.8 cells, at near-physiologic concentrations. Failure of the PTH analogues to block the effect of PTH on [Ca2+]i while inhibiting the effect on cAMP accumulation suggests separate pathways for PTH activation of adenylate cyclase and mobilization of calcium.
虽然甲状旁腺激素（PTH）对成骨细胞样细胞腺苷酸环化酶的刺激作用已广为人知，但PTH对胞质钙离子（[Ca2+]i）动员的影响仍存在争议，一组研究发现无影响，而其他研究则报告有不同程度的升高。我们研究了合成大鼠PTH片段1 - 34（rPTH(1 - 34)）以及两种抑制PTH对腺苷酸环化酶刺激作用的牛PTH类似物（牛8,18Nle，34Tyr - PTH(3 - 34)和34Tyr - PTH(7 - 34)）对[Ca2+]i的影响。在预先用发光光蛋白水母发光蛋白进行刮擦加载的灌注附着的大鼠成骨细胞样骨肉瘤细胞（ROS 17/2.8）中，在暴露于PTH类似物之前、期间和之后测量[Ca2+]i。静息[Ca2+]i为0.094±0.056微摩尔（平均值±标准差，n = 103），暴露于rPTH(1 - 34)后，[Ca2+]i以时间和剂量特异性方式升高。在10^(-10) M rPTH(1 - 34)时，[Ca2+]i在30秒内升高100%至平台期；更高浓度的PTH产生[Ca2+]i的初始峰值增加，随后是较低的平台期。在10^(-6) M时，初始峰值为基础值的5倍，即0.64±0.07微摩尔。两种PTH类似物都是[Ca2+]i动员的至少部分激动剂，并且在与rPTH(1 - 34)共同灌注时不会降低[Ca2+]i峰值。然而，这些类似物确实显著降低了rPTH(1 - 34)诱导的cAMP积累，并且自身不会增加cAMP积累。因此，rPTH(1 - 34)在接近生理浓度时能强烈动员ROS 17/2.8细胞中的[Ca2+]i。PTH类似物未能阻断PTH对[Ca2+]i的作用，同时却抑制了对cAMP积累的作用，这表明PTH激活腺苷酸环化酶和动员钙的途径是分开的。
