Desensitization of parathyroid hormone receptors on cultured bone cells.
Desensitization of parathyroid hormone receptors on cultured bone cells.
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培养骨细胞上甲状旁腺激素受体的脱敏。
DOI：
10.1002/jbmr.5650051202
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Arnaud,CD
中科院分区：
文献类型：
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作者：
Pun,KK;Ho,PW;Nissenson,RA;Arnaud,CD
在治疗骨质疏松症时给予过量的甲状旁腺激素（PTH）可以逆转低剂量间歇性方案的有益作用。为探讨甲状旁腺素（PTH）诱导PTH受体脱敏的直接作用及其可能的细胞机制，我们研究了脱敏对大鼠成骨细胞UMR-106的影响。当成骨细胞与bPTH-（1-34）预孵育时，在1小时内和低至5 nM的激素浓度下，对随后的激素挑战完全不应。当如此脱敏的成骨细胞在无激素培养基中孵育时，cAMP反应在2小时内开始恢复，并在16小时后达到最大值。放线菌酮不影响脱敏过程。[NIe8，Nie 18，Tyr 34]bPTH-（3-34）酰胺可显著削弱PTH-（1-34）的脱敏作用，但对cAMP反应无刺激作用。用异丙肾上腺素（50 μM）、前列腺素E（50 μM）或前列腺素E2（50 μM）预孵育2 h后，无明显异源脱敏。脱敏后与[125 I]PLP-（1-36）酰胺的结合实验显示，通过Scatchard分析，受体亲和力降低了约两倍，表明亲和力的降低在脱敏过程中非常显著。当细胞在脱敏过程中用莫能菌素处理时，脱敏后的PTH激发产生显著降低的环AMP反应。脱敏后16 h内恢复。列入莫能菌素，但不放线菌酮，损害恢复。结果表明，大鼠成骨细胞对PTH的同源脱敏是通过PTH-（1-34）占据受体而不是通过cAMP生成本身实现的。它主要不依赖于蛋白质合成或腺苷酸环化酶的激活。受体亲和力的降低在脱敏过程中是重要的。甲状旁腺激素受体的脱敏是增强和恢复受损的莫能菌素，抑制剂的内化和回收，表明这两个过程是重要的PTH受体的调节。
Administration of excessive amounts of parathyroid hormone (PTH) in the treatment of osteoporosis can reverse the beneficial effects of a low‐dose, intermittent regime. To investigate the direct actions and the possible cellular mechanisms of PTH in inducing desensitization of PTH receptors, we studied the effects of desensitization on rat osteoblastic UMR‐106 cells. When the osteoblasts were preincubated with bPTH‐(1–34), complete refractoriness to a subsequent challenge with the hormone developed within 1 h and at hormone concentrations as low as 5 nM. When osteoblasts thus desensitized were incubated in hormone‐free medium, recovery of the cAMP responses began within 2 h and reached maximum after 16 h. Cycloheximide did not affect the process of desensitization. [NIe8, NIe18, Tyr34]bPTH‐(3–34)amide significantly impaired the desensitization process by PTH‐(1–34) but did not have stimulatory effect on cAMP responses. No significant heterologous desensitization was obvious after preincubation with isoprenaline (50 μM), prostaglandin E, (50 μM), or prostaglandin E2(50 μM) for 2 h. Binding experiments with [125I]PLP‐(1–36)amide after desensitization revealed that there was an approximate twofold decrease in receptor affinities as analyzed by Scatchard analysis, showing that the decrease in affinity was prominent in the process of desensitization. When the cells were treated with monensin during desensitization, PTH challenge after desensitization produced significantly lower cyclic AMP responses. Recovery after desensitization occurred over a period of 16 h. Inclusion of monensin, but not cycloheximide, impaired the recovery. The results show that homologous desensitization of rat osteoblasts to PTH is brought about by the occupancy of receptors by PTH‐(1–34) but not by cAMP generation itself. It is not primarily dependent on protein synthesis or on activation of adenylate cyclase. A decrease in receptor affinity is important in the process of desensitization. Desensitization of parathyroid hormone receptors is potentiated and recovery impaired by monensin, an inhibitor of internalization and recycling, showing that both processes are important in the regulation of PTH receptors.