PATHOGENESIS OF HYPERCALCIURIA IN GENETIC IDIOPATHIC HYPERCALCIURIA RATS

该提案的长期目标是提高对以下方面的认识： 肠钙升高的发病机制和分子基础 遗传性特发性高钙尿症（IH）大鼠的转运，以及是否 这些发现被推广到人类IH。这群IH大鼠 以高钙尿、正常钙血症、十二指肠钙升高为特征 主动转运，正常血清1，25-二羟维生素D3 [1，25（OH）2D 3]和 含钙肾结石的自发形成。因此，IH大鼠 具有人类IH的许多特征。初步研究表明， 维生素D受体（VDR）结合含量增加两倍， 肠、肾和脾单核细胞。此外，本发明还提供了一种方法， 肠道VDR mRNA减少，而不是增加。这些数据构成了 肠上皮细胞VDR含量增加是一种表型标志物的假设 对于遗传性IH大鼠，VDR数量的增加调节， 增强1，25（OH）2D 3的生物学作用。如果增加的VDR 对于增加的肠钙吸收和高钙尿症至关重要， 则该假设将预测VDR增加是由于 正常或突变型VDR周转时间延长;较大VDR组织 含量增加维生素D依赖的生物功能;并且，VDR是 在所有表达VDR基因的组织中增加。以下3 设计了具体目标来检验总体假设： 1)探索IH大鼠VDR增加的机制：维生素 D-依赖性、组织分布和含量以及发育 VDR的出现;识别VDR基因外显子的异常 通过PCR扩增IH大鼠肠道VDR cDNA，测定VDR 消息稳定性和VDR周转率。 2)检测VDR增加的生物学功能， VDR的增加主要是通过：肠道内Ca的主动转运和VDR的含量 钙结合蛋白9 kd基因表达; 1，25（OH）2D 3诱导的脾细胞白细胞介素1-β（IL-1）基因抑制 单核细胞;颅骨骨钙素生成和24-羟化酶活性 骨细胞 3)采用项目3，测定大鼠睾丸组织中VDR含量及生物学功能， IH患者的可触及组织：制定VDR措施， 外周血单核细胞和EBV转化的淋巴母细胞;和 IL-1基因表达的1，25（OH）2D 3依赖性抑制。 拟议的研究应提供更详细的知识， 遗传性IH的发病机制和分子基础， 为人类遗传性IH提供了潜在的新的和有用的见解。

The long term goals of this proposal are to improve the understanding of the pathogenesis and molecular basis for the increased intestinal Ca transport in genetic idiopathic hypercalciuric (IH) rats and whether these: findings are generalized to human IH. This colony of IH rats is characterized by hypercalciuria, normocalcemia, elevated duodenal Ca active transport, normal serum 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] and spontaneous formation of Ca-containing kidney stones. Thus, the IH rats have many of the features of human IH. Preliminary studies demonstrate a two-fold increase in vitamin D receptor (VDR) binding content in intestine, kidney and splenic monocyte from IH rats. In addition, intestinal VDR mRNA is reduced, not increased. These data form the overall hypothesis that increased enterocyte VDR content is a phenotypic marker for genetic IH rats and that the increased VDR number modulates and amplifies the biologic action of 1,25(OH)2D3. If the increased VDR is critical for the increased intestinal Ca absorption and hypercalciuria, then the hypothesis would predict that the increased VDR is due to either prolongation of turnover of a normal or a mutant VDR; greater VDR tissue content increases vitamin D-dependent biologic functions; and, VDR is increased in all tissues that express the VDR gene. The following 3 specific aims are designed to test the overall hypothesis: 1) Explore the mechanisms whereby VDR is increased in IH rats by: vitamin D-dependence, tissue distribution and content, and developmental appearance of the VDR; identify abnormalities in the exons of the VDR gene of IH rats by PCR amplification of intestinal VDR cDNA; determine VDR message stability and VDR turnover. 2) Test the biological function of increased VDR in tissues in which the VDR is increased by: Ca active transport and VDR content in intestinal segments of high and low transport rates; calbindin 9kd gene expression; 1,25(OH)2D3-induced interleukin 1-beta (IL-1) gene suppression in splenic monocytes; osteocalcin production and 24-hydroxylase activity in calvarial bone cells. 3) With Project 3, determine VDR content and biologic function in accessible tissues from patients with IH: develop VDR measures in peripheral blood monocytes and EBV transformed lymphoblasts; and 1,25(OH)2D3-dependent suppression of IL-1 gene expression. The proposed studies should provide more detailed knowledge of the pathogenesis and molecular basis for genetic IH in the rat model and provide potentially new and useful insights into genetic human IH.