Regulation of Urea Transport in Diabetic Rat Kidney

描述(申请人提供)：糖尿病患者出现的多尿通常归因于渗透性利尿。然而，我们认为机制更为复杂。这项建议的主要目标是确定导致失控糖尿病患者水分和溶质稳态变化的细胞和分子机制。糖尿病中存在的几种代谢和激素异常可能会导致水分和溶质的损失，或者是限制这些损失的代偿机制。我们计划评估加压素和糖皮质激素在糖尿病大鼠调节髓质运输蛋白中的作用，因为这些动物(和人类)都有这两种激素的水平升高。我们还计划评估血管紧张素II的作用，因为它的抑制是目前糖尿病治疗的主要手段。识别这些机制可以为肾脏中必须发生的代偿机制提供新的见解，这些机制允许失控的I型糖尿病患者限制水分和溶质的损失，从而限制容量消耗。假说-肾脏对无法控制的糖尿病的一种代偿反应是改变髓质运输蛋白的表达和功能，以限制水分和溶质的损失。具体目标1：我们将测试尿素转运蛋白、水通道蛋白和离子通道或转运蛋白的表达是否在糖尿病失控的大鼠中发生变化。理论基础：我们有初步数据显示，糖尿病10-20天会导致UT-A1、AQP2和NKCC2/BSC1蛋白丰度增加。 具体目标2：我们将确定糖尿病大鼠在调节尿素、水和钠转运蛋白时对加压素和/或糖皮质激素的需求。理论基础：我们有初步数据表明，在没有糖皮质激素或加压素的情况下，UT-A1和AQP2蛋白的丰度不会增加。具体目标3：我们将确定阻断肾素-血管紧张素系统是否会改变糖尿病大鼠尿素、水和钠转运蛋白的调节。理论基础：阻断肾素-血管紧张素系统可能会阻止代偿性改变，加剧水分和溶质流失。具体目标4：我们将测试糖尿病大鼠的内髓集合管(IMCDs)中的加压素和/或血管紧张素II是否改变了尿素转运体的磷酸化或功能的快速调节。理论基础：血管紧张素II通过PKC增加大鼠IMCDs中UT-A1的磷酸化。我们有初步数据表明，抑制PKC减少了糖尿病大鼠内髓中UT-A1的磷酸化。

DESCRIPTION (provided by applicant): The polyuria that occurs in diabetic patients is generally ascribed to an osmotic diuresis. However, we believe that the mechanisms are more complex. The major goal of this proposal is to identify the cellular and molecular mechanisms that contribute to changes in water and solute homeostasis that occur in uncontrolled diabetes. Several metabolic and hormonal abnormalities present in diabetes could contribute to a loss of water and solute or compensatory mechanisms to limit these losses. We plan to evaluate the role of vasopressin and glucocorticoids in regulating medullary transport proteins in diabetic rats since these animals (and humans) have elevated levels of both hormones. We also plan to evaluate the role of angiotensin II since its inhibition is a mainstay of current therapy for diabetes. Identifying these mechanisms could provide novel insights into the compensatory mechanisms that must occur in the kidney that permit patients with uncontrolled type I diabetes to limit the loss of water and solute, thereby limiting volume depletion. HYPOTHESIS - A compensatory response by the kidney to uncontrolled diabetes is to alter the expression and function of medullary transport proteins to limit the loss of water and solute. Specific Aim 1: we will test whether expression of urea transporters, aquaporins, and ion channels or transporters are altered in rats with uncontrolled diabetes. Rationale: we have preliminary data showing that 10-20 days of diabetes results in an increase in UT-A1, AQP2, and NKCC2/BSC1 protein abundances. Specific Aim 2: we will determine the requirement for vasopressin and/or glucocorticoids in the regulation of urea, water, and sodium transporter proteins in rats with diabetes. Rationale: we have preliminary data showing that UT-A1 and AQP2 protein abundances do not increase in the absence of glucocorticoids or vasopressin. Specific Aim 3: we will determine whether blockade of the renin-angiotensin system alters the regulation of urea, water, and sodium transporter proteins in rats with diabetes. Rationale: blockade of the renin-angiotensin system may prevent compensatory changes and worsen water and solute loss. Specific Aim 4: we will test whether rapid regulation of urea transporter phosphorylation or function is altered by vasopressin and/or angiotensin II in inner medullary collecting ducts (IMCDs) from rats with diabetes. Rationale: angiotensin II increases phosphorylation of UT-A1 in rat IMCDs through PKC. We have preliminary data showing that PKC inhibition reduces UT-A1 phosphorylation in inner medulla from diabetic rats.