Renal Control of Blood Pressure in Early Diabetes

描述（由申请人提供）：我们已经证明，如果在慢性一氧化氮（NO）合成抑制的条件下发生，糖尿病中首次出现的高血糖症会引起显著的肾血管收缩和高血压。高血糖症的这些有害后果可以通过用超氧化物歧化酶模拟物tempol进行抗氧化处理来预防。潜在的假设是，早期糖尿病高血糖症的发生诱导血管紧张素II依赖性，超氧化物介导的肾压-尿钠排泄关系的右移，一氧化氮是预防高血压的重要抵消力量。本项目中的实验将通过检验一氧化氮抵消血管紧张素II依赖性、超氧化物介导的肾血管收缩以预防糖尿病早期高血糖期间的高血压的中心假设来确定这些重要相互作用的机制。实验将通过测试3个子假设来测试这一点：1。一氧化氮是预防糖尿病发作时肾血管收缩和高血压所必需的。我们的L-NAME、ACh和肾小球滤过率（GFR）数据支持这一点，但为了更好地揭示NO并确定其在早期糖尿病中控制肾功能的部位，我们将： a. 24小时/天测量肾血流量以量化阻力和滤过分数的变化; B.测定eNOS和nNOS的时间、葡萄糖和胰岛素依赖性变化; C.确定何时以及是否血管舒张的胰高血糖素承担NO的血管保护作用; D.使用敲除小鼠和输注拮抗剂确定eNOS相对于nNOS的作用。 2.血管紧张素II在高血糖期间增加对肾血管收缩和高血压的敏感性，并且是这些反应发生所必需的。我们的证据支持这一作用，但为了确定Angll的重要性独立于L-NAME诱导的增加，我们将确定： a.低钠摄入是否加重了糖尿病大鼠对NOS抑制的敏感性; B. GFR和血压之间的联系，通过减少肾脏质量来控制GFR; C.糖尿病的发作是否引起具有AngII高血压的大鼠的高血压; D. AngII的超氧化物非依赖性组分对MAP和肾阻力的影响。 3.超氧化物在高血糖症发作时诱导肾血管收缩剂和高血压影响。我们已经表明，tempol可以预防L-NAME治疗的糖尿病大鼠的高血压，但为了更具体地涉及SO，有或无NOS阻断，我们将确定： a.抗氧化剂治疗是否可以预防高血压而不降低肾素分泌; B. SO歧化酶-1（SOD 1）基因敲除是否加重高血压反应; C.转基因小鼠中增加的SOD 1是否与tempol类似地防止高血压; D. NADPH氧化酶的作用，通过测量p22 phox的表达和夹竹桃苷的影响。

DESCRIPTION (provided by applicant): We have shown that the first onset of hyperglycemia in diabetes causes significant renal vasoconstriction and hypertension if it occurs under conditions of chronic nitric oxide (NO) synthesis inhibition. Those deleterious consequences of hyperglycemia are prevented by antioxidant treatment with the superoxide (SO) dismutase mimetic, tempol. The underlying hypothesis is that onset of hyperglycemia in early diabetes induces an angiotensin II-dependent, superoxide-mediated right-shift in the renal pressure-natriuresis relationship, and that nitric oxide is an important counteracting force that prevents hypertension. The experiments in this project will determine the mechanisms for these important interactions by testing the central hypothesis that nitric oxide counteracts angiotensin II-dependent, superoxide-mediated renal vasoconstriction to prevent hypertension during hyperglycemia early in diabetes. Experiments will test this by testing the 3 subhypotheses that: 1. Nitric oxide is required to prevent renal vasoconstriction and hypertension at the onset of diabetes. Our L-NAME, ACh, and glomerular filtration rate (GFR) data support this, but to better implicate NO and define the site(s) for its control of renal function in early diabetes, we will: a. measure renal blood flow 24 hr/d to quantify the changes in resistance and filtration fraction; b. determine the time-, glucose-, and insulin-dependent changes in eNOS and nNOS; c. determine when, and if, vasodilatory prostaglandins assume the vasoprotective role of NO; d. determine the roles of eNOS vs. nNOS using knockout mice and infusion of antagonists. 2. Angiotensin II increases sensitivity to renal vasoconstriction and hypertension during hyperglycemia and is required for those responses to occur. Our evidence supports this role, but to determine Angll's importance independent of L-NAME-induced increases we will determine: a. whether low-sodium intake exacerbates the sensitivity of diabetic rats to NOS inhibition; b. the link between GFR and blood pressure by using decreased kidney mass to control GFR; c. whether onset of diabetes causes hypertension in rats with Angll hypertension; d. the superoxide-independent component of Angll's influence on MAP and renal resistance. 3. Superoxide induces a renal vasoconstrictor and hypertensive influence at the onset of hyperglycemia. We have shown that tempol prevents hypertension in L-NAME-treated diabetic rats, but to more specifically implicate SO, with or w/o NOS blockade, we will determine: a. whether antioxidant treatment can prevent hypertension without decreasing renin secretion; b. whether knockout of SO dismutase-1 (SOD1) exacerbates the hypertensive response; c. whether increased SOD1 in transgenic mice protects against hypertension similar to tempol; d. the role of NADPH oxidase, by measuring p22 phox expression and the effect of apocynin.