Metabolism of parathyroid hormone by fetal rat calvaria.
Metabolism of parathyroid hormone by fetal rat calvaria.
复制标题
胎鼠颅骨甲状旁腺激素的代谢。
作者：
J. Freitag;Kevin J. Martin;Mary B. Conrades;E. Slatopolsky
这些研究检查了胎鼠颅骨对高纯度牛甲状旁腺激素[bPTH-（1- 84）]的代谢。将酶促分散的骨细胞和完整的（切碎的）颅骨与bPTH-（1- 84）孵育，并通过聚丙烯酰胺凝胶电泳分析孵育培养基中PTH的降解。分析凝胶切片洗脱液中羧基和氨基末端RIA中的免疫反应性PTH（iPTH）。两种骨制剂均代谢bPTH-（1- 84）。完整的激素iPTH随着时间的推移而减少，孵育5分钟后，羧基末端iPTH片段明显。在分离的细胞制备物中，通过cAMP产生评估，在次最大剂量的PTH（5 × 10（-9）M）下，完整的激素完全降解。在研究的所有剂量下，完整颅骨制备物中的降解均不完全。完整的颅骨对PTH的cAMP产生不太敏感。在含有两种细胞制备物的培养基中均未检测到氨基末端片段。在这些系统中，氧化（无生物活性）bPTH-（1- 84）未代谢。这些发现与肝脏和肾脏制剂中的研究形成对比，其中氧化的bPTH已被证明是降解的。这些发现与肝脏和肾脏制剂中的研究形成对比，其中氧化的bPTH已被证明是降解的。这些数据表明，生物活性可能是骨细胞代谢完整bPTH-（1- 84）所必需的，骨骼组织可能导致大鼠循环PTH的免疫异质性。
These studies examine the metabolism of highly purified bovine parathyroid hormone [bPTH-(1--84)] by fetal rat calvaria. Enzymatically dispersed bone cells and intact (minced) calvaria were incubated with bPTH-(1--84) and the incubation medium was analyzed for degradation of PTH by polyacrylamide gel electrophoresis. Eluates of gel slices were assayed for immunoreactive PTH (iPTH) in carboxy- and amino-terminal RIAs. Both bone preparations metabolized bPTH-(1--84). The intact hormone progessively decreased with time and carboxy-terminal iPTH fragments were evident by 5 min of incubation. In the isolated cell preparations, intact hormone was completely degraded at submaximal doses of PTH (5 X 10(-9) M), as assessed by cAMP production. Degradation was incomplete in intact calvarial preparations at all doses studied. Intact calvaria were less sensitive to PTH with regard to cAMP production. No amino-terminal fragments were detected in the medium with either cell preparation. Oxidized (biologically inactive) bPTH-(1--84) was not metabolized in these systems. These findings contrast with studies in liver and kidney preparations, where oxidized bPTH has been shown to be degraded. These findings contrast with studies in liver and kidney preparations, where oxidized bPTH has been shown to be degraded. These data suggest that biological activity may be necessary for the metabolism of intact bPTH-(1--84) by bone cells and that skeletal tissue may contribute to the immunoheterogeneity of circulating PTH in the rat.