肾上腺切除对5/6肾切除大鼠肾脏的保护作用

目的通过切除5／6肾切除大鼠的肾上腺,探讨醛固酮对慢性肾脏疾病发生及发展的作用。方法雄性Wister大鼠分成5组:(1)假手术组(SHAM组);(2)5／6肾切除组(SNX组); (3)SNX+双肾上腺切除组(ADX组);(4)ADX+地塞米松组(DXM组);(5)ADX+地塞米松+醛固酮组(ALDO组)。所有大鼠自由饮用生理盐水,于成模第8周测定大鼠收缩压、各项血尿指标及肾小球硬化程度。应用Western印迹和实时定量PCR检测大鼠肾皮质TGF-β1、醛固酮受体 (MR)及保护MR的酶11β-羟类固醇脱氢酶2(11β-HSD2)的mRNA表达水平。结果 SNX组大鼠表现为明显的白蛋白尿、高血压、肾小球硬化、肾皮质TGF-β1表达升高,血醛固酮水平是 SHAM组的4倍以上。与SNX组比较,ADX组大鼠血浆醛固酮水平明显下降,同时病变明显改善 尿白蛋白(mg／24 h)19．7±2．0比31．7±1．7,P<0．01;收缩压(mmHg)173．8±4．3比210．4±4．1,P <0．01;肾小球硬化指数38．2±7．9比92．3±6．7,P<0．01;TGF-β1 3．8±0．6比10．3±1．2,P< 0．01]。ALDO组的血浆醛固酮水平为SHAM组的近2倍,与ADX组比较,以上病变又加重尿白蛋白(mg／24 h)24．9±1．4,收缩压(mmHg)201．5±4．5,肾小球硬化指数88．1±7．2,TGF-β1 5．8± 0．6,P均<0．01]。肾脏皮质MR mRNA在SNX组的表达明显增加;在ADX组明显下降SNX(复制数／百万GAPDH)39866．7±10579．0比SHAM 2366．7±446．3,P<0．05;比ADX 22100．0±4435．7, P<0．05]。然而,11β-HSD2 mRNA表达和MR相反,SNX组为9150．0±969．9,明显低于SHAM组 (48100．0±9315．2,P<0．05);而ADX组的表达比SNX组显著升高(30066．7±5150．2,P<0．05)。 4个实验组大鼠肾脏Ccr和肾重／体重无显著性差别。结论醛固酮参与慢性肾脏病变的进展, 其对肾小球损伤的作用除血流动力学效应外,还可能存在非血流动力学的直接致纤维化作用。

Ameliorative effect of adrenalectomy on remnant nephropathy in the rat depends on aldosterone level

Objective To examine the hypothesis that the ameliorative effect of adrenalectomy on remnant nephropathy rats depends on low aldosterone level. Methods Male Wistar rats weighing 180~200 g were divided into the following 5 groups:SHAM rats，5/6 nephrectomy rats (SNX group)， nephrectomy and adrenalectomized rats (ADX group)， bi-ectomized rats infused with exogenous dexamethasone (DXM group) or plus aldosterone (ALDO group) by osmotic mini-pump at 12 μg•kg-1•d-1 and 40 μg•kg-1•d-1， respectively. They had free access to saline and were sacrificed at week 8. Results 5/6 rats had marked proteinuria，hypertension，glomerulosclerosis and up-regulated expression of TGF-β1 as high as > 4-fold elevation in renal cortex in plasma aldosterone as compared to those of the SHAM rats. The above pathologies were markedly improved in bi-ectomised rats with significantly lower aldosterone level. Being constantly infused exogenous aldosterone， bi-ectomized rats manifested greater proteinuria，hypertension，glomerulosclerosis and increased level of TGF-β1 compared to bi-ectomised rats. Indeed， these features were similar in exogenous aldosterone rats and 5/6 nephrectomized rats. Furthermore， the expression of mineralocorticoid receptor (MR) mRNA was remarkablely enhanced in SNX group and was decreased in ADX group. However， the mRNA expression of 11β-hydroxysteroid dehydrogenase Ⅱ (11β-HSD2) in each group was opposite to that of MRmRNA. Ccr and kidney/body weight showed no differences among four experimental groups. Conclusion Aldosterone contributes to the progression of ablative nephropathy in the rat through mechanisms other than systolic blood pressure.