RAT INTESTINAL MEMBRANE--VITAMIN D-MEDIATED EFFECTS

我们实验室在上一个资助周期的先前研究 证明体外添加1，25（OH）2D 3（10-（8）至10-（11）） M）快速（秒至分钟）刺激磷酸肌醇周转，激活 PKC，增加[Ca 2 +]（i）和降低[pH]（i），通过抑制 Na+/H+交换，在维生素D充足的大鼠和 在CaCo-2细胞中。 此外，1，25（OH）2D 3和氯乙烷甲胆碱 未能引出任何上述结肠生化 D缺乏大鼠的反应。 在体内补充这些缺乏D- 然而，用1，25（OH）2D 3处理5至7天的动物， 体外1，25（OH）_2D_3和氨甲酰甲胆碱的生化效应 器官. 根据这些先前的发现， 目前的建议是：1）进一步阐明所涉及的机制， 1，25（OH）2D 3对磷酸肌醇信号的快速体外作用 维生素D充足大鼠大肠中的转导系统 和CaCo-2细胞中; 2）进一步表征生理学特征， 1，25（OH）2D 3的这些快速体外生化作用的结果 在维生素D充足大鼠的大肠和CaCo-2细胞中; 和3）确定负责这些损失的机制 1，25（OH）_2D_3在维生素大肠中的快速体外作用 D-缺陷动物及其通过体内施用 1，25（OH）2D3。 人们强烈期望， 这些具体的目标应该增加我们的知识， 1，25（OH）2D 3的作用机制和生理效应 细胞

Prior studies by our laboratory during the last grant cycle have demonstrated that the in vitro addition of 1,25(OH)2D3 (10-(8) to 10-(11) M) rapidly (sec to min) stimulated phosphoinositide turnover, activated PKC, increased [Ca2+](i) and decreased [pH](i), via inhibition of the Na+/H+ exchange, in the large intestine of vitamin D-sufficient rats and in CaCo-2 cells. Furthermore, 1,25(OH)2D3 and bethanechol chloride failed to elicit any of these aforementioned colonic biochemical responses in D-deficient rats. In vivo repletion of these D-deficient animals with 1,25(OH)2D3 for 5 to 7 days, however, restored the rapid biochemical effects of in vitro 1,25(OH)2D3 and bethanechol in this organ. Based on these prior findings, the three major specific aims of the present proposal are to: 1) further elucidate the mechanisms involved in the rapid, in vitro actions of 1,25(OH)2D3 on the phosphoinositide signal transduction system in the large intestine of vitamin D-sufficient rats and in CaCo-2 cells; 2) further characterize the physiological consequence of these rapid, in vitro biochemical actions of 1,25(OH)2D3 in the large intestine of vitamin D-sufficient rats and in CaCo-2 cells; and 3) determine the mechanism(s) responsible for the loss of these rapid, in vitro actions of 1,25(OH)2D3 in the large intestine of vitamin D-deficient animals and their correction by in vivo administration of 1,25(OH)2D3. It is strongly anticipated that the successful achievement of these specific aims should increase our knowledge with respect to the mechanisms of action and physiological effects of 1,25(OH)2D3 in these cells.