PATHOGENESIS OF HYPERCALCIURIA IN GENETIC IDIOPATHIC HYPERCALCIURIA RATS

这项建议的长期目标是提高对 肠易激综合征发病机制及分子基础的研究 遗传性特发性高钙尿症(IH)大鼠的转运及其是否 这些：这些发现被推广到人类IH。这群IH大鼠 特点是高钙尿，正常血钙，十二指肠钙化 主动转运，正常血清1，25-二羟基维生素D3[1，25(OH)2D3]和 含钙肾结石的自发形成。因此，IH大鼠 具有许多人类IH的特征。初步研究表明， 维生素D受体(VDR)结合含量增加两倍 来自IH大鼠的肠、肾和脾单核细胞。此外, 肠道VDR基因表达减少，而不是增加。这些数据构成了总体 肠细胞VDR含量增加是表型标志物的假说 对于遗传性IH大鼠，VDR数量的增加调制和 放大1，25(OH)2D3的生物作用。如果增加的VDR是 对肠道钙吸收增加和高钙尿症至关重要， 那么假说就会预测VDR的增加是由于 正常或突变VDR的周转时间延长；VDR组织较大 维生素D的含量增加了依赖维生素D的生物功能；VDR是 在所有表达VDR基因的组织中都增加了。以下3项 具体目标旨在检验总体假设： 1)探讨维生素增加IH大鼠VDR的机制： D依赖、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 用聚合酶链式反应扩增大鼠肠道VDR基因，测定VDR 消息稳定性和VDR周转率。 2)测试VDR增加在组织中的生物学功能 VDR增加的原因是：肠道CA主动转运和VDR含量增加 高、低转运率片段；Calbindin 9kd基因表达； 1，25(OH)2D3诱导的脾组织IL-1基因抑制 单核细胞；颅骨中骨钙素的产生和24-羟基酶活性 骨细胞。 3)结合项目3，确定VDR含量和生物功能 IH患者可获得的组织：制定VDR措施 外周血单核细胞和EBV转化的淋巴母细胞； 1，25(OH)2D3依赖抑制IL-1基因表达。 建议的研究应提供更详细的知识 遗传性高血压大鼠的发病机制及其分子基础 为人类IH的基因研究提供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.