肾上腺切除对5／6肾切除大鼠肾脏的保护作用

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

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。

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,glomenalosclerosis 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.