HORMONAL REGULATION OF BONE GROWTH IN VIVO

这一建议是基于以前的观察，即低剂量的 间歇性甲状旁腺激素（PTH）增加体内骨量。 了解调节合成代谢作用的机制和介质 将允许一个更合理的方法来使用PTH治疗 骨质疏松症，并可能提出新的方法来增加骨量， 补偿病理性骨质流失。 我们假设PTH在体内的合成代谢作用是由 生长激素依赖性胰岛素样生长因子I（IGF-I）。 目标 第一项研究的目的是确定PTH是否选择性地增加mRNA， 骨小梁中IGF-I和IGF-BPs的蛋白质 用溶剂或 PTH单独或与GH联合给药1、3、5或12天。 远侧 将股骨分为骨小梁、皮质和骨髓 隔室和IGF-I的变化将在时间上与 PTH受体mRNA的可能变化，替代假定介质， IGF-II、TGF β和PGH合酶、基质蛋白、前胶原1 α（I） 和骨钙素，使用半定量RT-PCR，溶液- 杂交/核酸酶保护测定或北方印迹杂交。 这些mRNA随时间的变化将与细胞凋亡的增加有关。 骨形成表面的百分比。 在第二项研究中， 将使用组织杂交来检测所述蛋白的空间表达。 并确定细胞的相对位置 表达生长因子mRNA的细胞和表达PTH受体的细胞，或 腰椎骨小梁中的骨基质蛋白。 空间 分泌IGF-I和IGF-BP的骨小梁细胞的位置将被 用免疫细胞化学鉴定。 第三项研究的目标是， 确定IGF-I单克隆抗体或过量IGF-BP是否会阻断 局部注入一侧股骨远端时PTH的合成代谢作用 vivo. 将通过定量X线摄影监测骨密度;骨 矿物质含量将通过单光子吸收法（SPA）测量; 和骨形成。 第四个目标 这项研究是为了确定是否有时间或位置的变化，在mRNA的 IGF-I、IGF-II、IGF-BP、TGF β、PGH合酶和PTH受体或 动物模型中IGF-I、IGF-BP或PGH合酶的蛋白质合成， 例如输注PTH的甲状腺-甲状旁腺切除大鼠或老年大鼠 给予间歇性PTH，其中我们已经显示了合成代谢反应， PTH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.