METABOLISM OF LEAD IN BONE

骨骼是人体铅(铅)储存的主要储存库； 现在人们认识到，基于体内和体外的数据， 骨铅的一个骨骼亚室很容易被交换 并以与钙(Ca)类似的方式进行调节。 此外，骨架是CaNa2EDTA与铅的络合部位； 最近对儿童的临床观察表明， 骨骼是铅毒性作用的目标组织。在这个范围内 背景下，我们实验室的主要工作是测试 假设细胞内钙动态平衡的扰动， 在相对较低的浓度下由铅产生，是一种早期的 铅毒性在细胞水平的离散表达。是这样的 扰动可能会影响深远，并可能使 生理外的多种细胞过程的调节 通过细胞内离子钙变化进行正常控制的范围 集中精神。我们在小学进行的实验 单层培养分离的破骨细胞(OC)和 成骨细胞(OB)骨细胞，在之前的赠款期间， 进一步确认并扩展这一假设，直到它 现在可以直接验证了。该提案的具体目的 主要目的是：1)表征稳态动力学分布和 通过去饱和技术对OB中铅和钙的调节； 用~(19)F核磁共振法直接测定细胞内游离离子浓度 钙和铅在有铅和无铅的OC和OB中同时存在(和 促钙激素)；3)确定特定的 膜水平上铅-钙相互作用机制的研究 运输，其中铅对钙运输的影响 将在静息和荷尔蒙刺激下检查胎膜 OC和OB；4)确定铅对钙介导的细胞的影响 功能与cAMP的产生和降解；5) 进一步刻画铅对铅的综合作用的影响 OC和OB分别和一起进行共培养实验。 综合来看，拟议的量化、机械化和 OB和OC的功能研究有真正的潜力来定义， 第一次，早期铅中毒的分子基础 细胞水平。

Bone is the major reservoir of body lead (Pb) stores in humans; and it is now recognized, based upon in vivo and in vitro data, that one skeletal subcompartment of bone Pb is readily exchangeable and modulated in a manner similar to that of calcium (Ca). Moreover, the skeleton is the site of Pb chelation by CaNa2EDTA; and recent clinical observations in children indicate that the skeleton is a target tissue for Pb's toxic effects. Within this context, our laboratory's primary efforts are directed at testing the postulate that pertubations in cellular Ca homeostasis, produced by Pb at relatively low concentrations, is an early and discrete expression of Pb toxicity at the cellular level. Such pertubations are likely to be far reaching and may place the regulation of multiple cellular processes out of the physiological range of normal control through changes in intracellular ionic Ca concentration. Experiments carried out by us in primary monolayer cultures of separated osteoclastic (OC) and osteoblastic (OB) bone cells, during the previous grant period, further confirm and extend this postulate to the point where it can now be verified directly. The specific aims of the proposal are to: 1) characterize the steady state kinetic distribution and modulation of Pb and Ca in OB by desaturation techniques; 2) measure directly by 19F NMR the concentration of cytosolic free Ca and Pb concurrently in OC and OB with and without Pb (and calciotropic hormones) in the medium; 3) determine the specific mechanisms of Pb-Ca interactions at the level of membrane transport, where Pb effects on Ca transport in isolated membranes will be examined in resting and hormonally stimulated OC and OB; 4) define the effects of Pb on Ca-mediated cell functions and the generation and degradation of cAMP; 5) characterize further Pb influences on the integrated functions of OC and OB separately and together in co-culture experiments. Taken together, the proposed quantitative, mechanistic and functional studies in OB and OC have the real potential to define, for the first time, the molecular basis of early Pb toxicity at the cellular level.