HORMONAL REGULATION OF BONE GROWTH IN VIVO

这一建议是基于之前的观察结果，即低剂量的 间歇性甲状旁腺激素(PTH)可增加体内骨量。 对调节合成代谢作用的机制和介体的认识 甲状旁腺激素的使用将允许一种更合理的方法来使用甲状旁腺素治疗 骨质疏松症，并可能提出增加骨量的新方法 补偿病理性骨丢失。 我们推测甲状旁腺素在体内的合成代谢作用是通过 生长激素依赖型胰岛素样生长因子I(IGF-I)。目标是 第一项研究的目的是确定甲状旁腺激素是否选择性地增加mRNA和 骨小梁中IGF-I和IGF结合蛋白(IGF-Bps)的表达 对年轻的完整和去垂体组(HX)大鼠用赋形剂或 甲状旁腺素单独或联合生长激素治疗1、3、5或12天。远端 股骨将被分成骨小梁、皮质和骨髓 IGF-I的分区和变化将在时间上与 甲状旁腺激素受体可能的mRNA变化， IGF-II、TGFβ和PGH合成酶、基质蛋白、前胶原1α(I) 和骨钙素，用半定量RT-PCR测定，溶液- 杂交/核酸酶保护试验或Northern印迹杂交。 这些mRNAs随时间的变化将与 骨形成表面的百分比。在第二项研究中，原位 组织杂交将被用来检测该基因的空间表达 选择的mRNA并确定细胞的相对位置 表达生长因子mRNA和表达甲状旁腺素受体或 腰椎小梁骨中的骨基质蛋白。空间 分泌IGF-I和IGF-Bps的骨小梁细胞的位置将是 用免疫细胞化学鉴定。第三项研究的目标是 确定IGF-I单抗或过量的IGF-BP是否会阻断 单侧股骨远端局部注射甲状旁腺素的合成代谢作用 活着。骨密度将通过定量放射摄影术进行监测； 矿物含量将通过单光子吸收法(SPA)进行测量； 骨组织形态计量学测定骨形成。第四届奥运会的目标 研究是确定在mRNA中是否存在时间或位置的变化 IGF-I、IGF-II、IGF-Bps、TGFbeta、PGH合成酶和PTH受体或 动物模型中IGF-I、IGF-Bps或PGH合成酶的蛋白质合成 如甲状旁腺切除后注入甲状旁腺激素的大鼠或老年大鼠 在给定的间歇性PTH中，我们已经显示出合成代谢反应 甲状旁腺素缺失或钝化。

This proposal is based on previous observations that low doses of intermittent parathyroid hormone (PTH) increase bone mass in vivo. Knowledge of mechanisms and mediators which regulate the anabolic effect of PTH will permit a more rational approach to using PTH to treat osteoporosis, and may suggest new approaches to increasing bone mass to compensate for pathologic bone loss. We hypothesize that the anabolic effect of PTH in vivo is mediated by growth hormone-dependent insulin-like growth factor I (IGF-I). The goal of the first study is to determine if PTH selectively increases mRNA and protein for IGF-I and IGF-binding proteins (IGF-BPs) in trabecular bone of young intact and hypophysectomized (HX) rats treated with vehicle or PTH alone or in combination with GH for 1, 3, 5 or 12 days. distal femurs will be separated into trabecular, cortical and marrow compartments and changes in IGF-I will be correlated in time with possible changes in mRNA for PTH receptor, alternate putative mediators, IGF-II, TGFbeta and PGH synthase, matrix proteins, procollagen 1alpha(I) and osteocalcin, measured using semi-quantitative RT-PCR, solution- hybridization/nuclease protection assays or Northern blot hybridization. Changes in these mRNAs with time will be related to the increase in percent of bone forming surfaces. In the second study, in situ histohybridization will be used to detect the spatial expression of the selected mRNAs and to determine the relative locations of cells expressing growth factor mRNA and those expressing the PTH receptor or the bone matrix proteins in trabecular bone of lumbar vertebrae. Spatial location of trabecular bone cells secreting IGF-I and IGF-BPs will be identified using immunocytochemistry. the goal of the third study is to determine if IGF-I monoclonal antibody or excess IGF-BPs will block the anabolic effect of PTH when infused locally into one distal femur in vivo. Bone density will be monitored by quantitative radiography; bone mineral content will be measured by single photon absorptiometry (SPA); and bone formation by bone histomorphometry. The goal of the fourth study is to determine if there are shifts in time or location in mRNA for IGF-I, IGF-II, IGF-BPs, TGFbeta, PGH synthase and PTH receptor or in protein synthesis of IGF-I, IGF-BPs or PGH synthase in animal models, such as thyroid-parathyroidectomized rats infused with PTH or aged rats given intermittent PTH, in which we have shown the anabolic response to PTH to be absent or blunted.