van Leeuwen J P, Birkenhäger J C, Schilte J P, Buurman C J, Pols H A
Department of Internal Medicine III, Erasmus University Medical School, Rotterdam, The Netherlands.
Cell Calcium. 1990 Apr;11(4):281-9. doi: 10.1016/0143-4160(90)90005-f.
To understand further the mechanism of action of parathyroid hormone (PTH) in the stimulation of the number of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) binding sites in UMR 106-01 cells we studied the role of cAMP and calcium. In addition to PTH other agents known to act via the cAMP signal pathway, prostaglandin E2, forskolin and dibutyryl cAMP, caused an increase in 1,25(OH)2D3 binding. Addition of the adenylate cyclase inhibitor 9-(tetrahydro-2-furyl)adenine resulted in a marked decrease of PTH-stimulated cAMP production but this was not followed by a reduction of 1,25(OH)2D3 receptor up-regulation by PTH. Increasing the intracellular calcium concentration by Bay K 8644 and A23817 independent of an activation of the cAMP signal pathway did not result in an increased 1,25(OH)2D3 binding. The calcium channel blockers nitrendipine and verapamil and chelating extracellular calcium with EGTA all reduced cAMP-mediated stimulation of 1,25(OH)2D3 binding. This reduction was not due to a reduce cAMP production as verapamil even potentiated PTH- and forskolin-stimulated cAMP production in a dose-dependent manner. The present study provides evidence for an interrelated action of calcium and cAMP in the heterologous up-regulation of the 1,25(OH)2D3 receptor. The current data show an interaction between the cAMP and calcium signal pathway at (1) the level of cAMP generation/degradation, and (2) a level located distal in the cascade leading to 1,25(OH)2D3 receptor up-regulation.
为了进一步了解甲状旁腺激素（PTH）刺激UMR 106 - 01细胞中1,25 - 二羟基维生素D3（1,25(OH)2D3）结合位点数量的作用机制，我们研究了环磷酸腺苷（cAMP）和钙的作用。除PTH外，已知通过cAMP信号通路起作用的其他试剂，如前列腺素E2、福斯可林和二丁酰环磷腺苷，均可使1,25(OH)2D3结合增加。添加腺苷酸环化酶抑制剂9 -（四氢 - 2 - 呋喃基）腺嘌呤会导致PTH刺激的cAMP生成显著减少，但这并未伴随PTH对1,25(OH)2D3受体上调作用的降低。通过Bay K 8644和A23817增加细胞内钙浓度，而不依赖于cAMP信号通路的激活，并未导致1,25(OH)2D3结合增加。钙通道阻滞剂尼群地平和维拉帕米以及用乙二醇双四乙酸（EGTA）螯合细胞外钙均降低了cAMP介导的1,25(OH)2D3结合刺激。这种降低并非由于cAMP生成减少，因为维拉帕米甚至以剂量依赖性方式增强了PTH和福斯可林刺激的cAMP生成。本研究为钙和cAMP在1,25(OH)2D3受体异源上调中的相互关联作用提供了证据。目前的数据表明，cAMP和钙信号通路在以下两个方面存在相互作用：（1）cAMP生成/降解水平；（2）在导致1,25(OH)2D3受体上调的级联反应中位于下游的一个水平。
