IN VITRO AND IN VIVO STUDIES OF LEAD AND ITS COMPLEXES

描述（改编自研究者摘要）：暴露 儿童对环境源的铅是一个严重的公共健康 关心 治疗铅中毒的医疗方法越来越多地使用 螯合治疗与meso-DMSA（琥珀），一个相对无毒，口服 螯合剂被FDA授予孤儿药地位。 临床 在四个医疗保健中心进行的试验，包括肯尼迪克里格研究所， 约翰霍普金斯，正在评估中-DMSA的有效性。 尽管 这种治疗剂的重要性，吸收数据， meso-DMSA及其铅配合物的分布、代谢和消除 是有限的。 仍然需要关键的知识， 制定有效的治疗策略。 例如，内消旋-DMSA是 推测其在体内与易接近的铅络合，允许尿排泄。 然而，这一过程尚未得到验证，中位DMSA可能会或可能不会 是体内铅的活性螯合剂。 我们假设放射性示踪剂技术可以澄清基本的 meso-DMSA及其代谢产物与Pb形成配合物的研究进展 在体外和体内。 我们的目标是确定在体内形成的复合物 在服用meso-DMSA后出现铅中毒 我们建议使用放射性 铅（Pb-203），结合非放射性和同位素标记 (C-13和C-14）meso-DMSA，用于复合物的体外和体内研究 参与小鼠模型中的铅排泄。 我们的工作计划要求：（1） 内消旋和外消旋铅配合物合成与表征 外消旋DMSA、1：2 DMSA：半胱氨酸加合物和半胱氨酸; 2）小鼠 放射性铅络合物在体内的生物分布研究，包括双 同位素（Pb-203/C-14）实验; 3）分析铅络合物形成的， 通过与表征的标准品的相关性在小鼠尿液中的体内分析和4）分析 接受螯合治疗的病人尿中铅复合物的含量。 初步的研究工作包括：1）合成了Pb-203配合物， 和外消旋DMSA; 2）全身和局部脑 “游离”Pb-203和Pb-203-DMSA络合物在小鼠体内的生物分布研究; 3)小鼠脑中“游离”Pb-203的离体放射自显影;以及4） 建立了小鼠体内尿铅排泄模型， 内消旋-DMSA的存在和不存在，其应提供足够的量 用于分析。 我们的工作为开发药物动力学模型奠定了基础。 螯合疗法

DESCRIPTION (Adapted from the Investigator's Abstract): Exposure of children to environmental sources of lead is a serious public health concern. Medical approaches to treatment of lead poisoning increasingly use chelation therapy with meso-DMSA (Succimer), a relatively non-toxic, orally available chelating agent granted Orphan Drug Status by the FDA. Clinical trials at four health care centers, including Kennedy Krieger Institute at Johns Hopkins, are evaluating the effectiveness of meso-DMSA. Despite the significance of this therapeutic agent, data on the absorption, distribution, metabolism and elimination of meso-DMSA and its Pb complexes are limited. Critical knowledge is still needed that could aid in the development of efficient treatment strategies. For example, meso-DMSA is presumed to complex accessible lead in vivo, allowing urinary excretion. However, this process has yet to be validated, and meso-DMSA may or may not be the active chelating agent for lead in vivo. We hypothesize that radioactive tracer technologies can clarify fundamental aspects of the formation of Pb complexes with meso-DMSA and its metabolites in vitro and in vivo. Our goal is to identify the complexes formed in vivo with lead upon administration of meso-DMSA. We propose to use radioactive lead (Pb-203), in conjunction with non-radioactive and isotopically labeled (C-13 and C-14) meso-DMSA, for in vitro and in vivo studies of the complexes involved in lead excretion in a murine model. Our work plan requires 1) the synthesis and chemical characterization of Pb-complexes with meso- and racemic DMSA, the 1:2 DMSA:cysteine adduct, and cysteine; 2) mouse biodistribution studies of radioactive Pb-complexes in vivo, including dual isotope (Pb-203/C-14) experiments; 3) analysis of lead complexes formed in vivo in mouse urine by relation to characterized standards and 4) analysis of lead complexes in urine from patients receiving chelation therapy. Preliminary studies include: 1) the synthesis of Pb-203 complexes of meso- and racemic DMSA by novel Chelex methods; 2) whole-body and regional brain biodistribution studies of "free" Pb-203 and Pb-203-DMSA complexes in mouse; 3) ex vivo autoradiography of "free" Pb-203 in mouse brain; and 4) establishment of a murine model of urinary excretion of lead in vivo, in the presence and absence of meso-DMSA, that should provide sufficient quantities of metabolites for analysis. Our work sets the stage for development of a pharmacokinetic model of chelation therapy.