INTESTINAL CA2+ TRANSPORT: VITAMIN D-DEPENDENT MECHANISM

肠道 CA2 转运：维生素 D 依赖性机制

• 批准号: 3230776
• 负责人: MILTON M WEISER
• 金额: $ 7.47万
• 依托单位: STATE UNIVERSITY OF NEW YORK AT BUFFALO
• 依托单位国家: 美国
• 财政年份: 1983
• 资助国家: 美国
• 起止时间: 1983-04-01 至 1989-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/3230776
• 关键词: 1,25 dihydroxycholecalciferol; Golgi apparatus; basolateral membrane; calcium disorder; calcium metabolism; cell membrane; dietary calcium; gastrointestinal epithelium; gastrointestinal nutrient absorption; membrane permeability; messenger RNA; nephrolithiasis; nutrition related tag; osteoporosis; vitamin D

In previous studies on the mechanism of vitamin D-dependent Ca2+ transport across the intestine, we prepared membrane vesicles from rat intestinal epithelial cells (enterocytes) and observed that Golgi membrane vesicles demonstrated the highest Ca2+ uptake when compared with lateral-basal (L-B) and microvillus (MV) membrane vesicles. This Ca2+ uptake was specifically dependent on 1,25(OH)2D3, the active metabolite of vitamin D. Recent studies, supported by this grant, have shown that this Ca2+ uptake was due to binding to non-esterified fatty acids (NEFAs) in the membranes and was associated with an increased phospholipase A activity. Membranes prepared from isolated enterocytes had markedly decreased Ca2+ binding and better demonstrated a vitamin D-dependent ATP-requiring Ca2+ uptake, particularly for duodenal villus cells (as contrasted with crypt cells). To pursue these findings further we propose: 1) to define the role of NEFAs, phospholipids and phospholipases in the molecular mechanisms of sequestering calcium during its absorption by the intestine, 2) to purify the Ca2+-ATPase of L-B membrane presumed responsible for ATP-dependent Ca2+ uptake, and 3) to study the molecular mechanisms by which 1,25(OH)2D3 effects Ca2+-ATPase function by either a genomic mechanism or through a post-translational activation of the enzyme. We will also try to determine if 1,25-(OH)2D3 stimulates the synthesis or appearance of proteins in Golgi and L-B membrane important to lipid metabolism. The effect of 1,25(OH)2D3 on the mRNA for Ca2+-ATPase will be studied. Changes in these parameters as related to enterocyte differentiation will be emphasized. Since there is evidence that 1,25(OH)2D3-dependent calcium transport is, in fact, dependent on enterocyte differentiation, it seems an ideal system for increasing our understanding of differentiation and tissue organization in relationship to a specific intestinal function. Regulation of intestinal calcium transport is fundamental to calcium homeostasis. Therefore, these studies will help in understanding the pathophysiology of osteoporosis, kidney stones, and the effects of intestinal diseases on calcium absorption and calcium metabolism.

以往关于维生素D依赖性Ca2+转运机制的研究 穿过肠道，我们从大鼠肠道中制备了膜囊泡 上皮细胞（肠上皮细胞）并观察到高尔基体膜囊泡 与横向基础 (L-B) 相比，表现出最高的 Ca2+ 吸收 和微绒毛（MV）膜囊泡。 这种 Ca2+ 吸收是专门 依赖于 1,25(OH)2D3，维生素 D 的活性代谢物。最近 此项资助支持的研究表明，Ca2+ 的吸收是由于 与膜中的非酯化脂肪酸（NEFA）结合， 与磷脂酶 A 活性增加有关。 膜准备好 来自分离的肠细胞的 Ca2+ 结合显着降低，并且更好 证明了维生素 D 依赖性 ATP 需要 Ca2+ 吸收，特别是 对于十二指肠绒毛细胞（与隐窝细胞相比）。 追求 我们进一步建议这些发现：1）定义 NEFA 的作用， 磷脂和磷脂酶的分子机制 在肠道吸收钙的过程中隔离钙，2) 净化 L-B 膜的 Ca2+-ATP 酶被认为负责 ATP 依赖性 Ca2+ 摄取，以及 3) 研究 1,25(OH)2D3 的分子机制 通过基因组机制或通过 酶的翻译后激活。 我们还将尝试确定 如果 1,25-(OH)2D3 刺激高尔基体中蛋白质的合成或出现 L-B膜对脂质代谢很重要。 1,25(OH)2D3 的作用 将研究 Ca2+-ATPase mRNA 的变化。 这些参数的变化 将强调与肠上皮细胞分化相关的问题。 自从那里 证据表明 1,25(OH)2D3 依赖性钙转运实际上是 依赖于肠细胞分化，这似乎是一个理想的系统 增加我们对分化和组织组织的理解 与特定肠道功能的关系。 调节肠道 钙转运是钙稳态的基础。 因此，这些 研究将有助于了解骨质疏松症的病理生理学， 肾结石以及肠道疾病对钙吸收的影响 和钙代谢。