Kobori Hiroyuki, Harrison-Bernard Lisa M, Navar L Gabriel
Department of Physiology, Tulane University School of Medicine, New Orleans, Louisiana.
J Am Soc Nephrol. 2001 Mar;12(3):431-439. doi: 10.1681/ASN.V123431.
Chronic elevations in circulating angiotensin II (AngII) levels produce sustained hypertension and increased intrarenal AngII contents through multiple mechanisms, which may include sustained or increased local production of AngII. This study was designed to test the hypothesis that chronic AngII infusion increases renal angiotensinogen mRNA and protein levels, thus contributing to the increase in intrarenal AngII levels. AngII (80 ng/min) was infused subcutaneously for 13 d into Sprague-Dawley rats, using osmotic minipumps. Control rats underwent sham operations. By day 12, systolic arterial BP increased to 184 +/- 3 mmHg in AngII-treated rats, whereas values for sham-treated rats remained at control levels (125 +/- 1 mmHg). Plasma renin activity was markedly suppressed (0.2 +/- 0.1 versus 5.3 +/- 1.2 ng AngI/ml per h); however, renal AngII contents were significantly increased in AngII-treated rats (273 +/- 29 versus 99 +/- 18 fmol/g). Western blot analyses of plasma and liver protein using a polyclonal anti-angiotensinogen antibody demonstrated two specific immunoreactive bands, at 52 and 64 kD, whereas kidney tissue exhibited one band, at 52 kD. Densitometric analyses demonstrated that AngII infusion did not alter plasma (52- or 64-kD), renal (52-kD), or hepatic (52-kD) angiotensinogen protein levels; however, there was a significant increase in hepatic expression of the highly glycosylated 64-kD angiotensinogen protein, of almost fourfold (densitometric value/control value ratios of 3.79 +/- 1.16 versus 1.00 +/- 0.35). Renal and hepatic expression of angiotensinogen mRNA, which was examined by semiquantitative reverse transcription-PCR, was significantly increased in AngII-treated rats, compared with shamtreated rats (kidney, densitometric value/glyceraldehyde-3-phosphate dehydrogenase mRNA value ratios of 0.82 +/- 0.11 versus 0.58 +/- 0.04; liver, densitometric value/glyceraldehyde-3-phosphate dehydrogenase mRNA value ratios of 2.34 +/- 0.07 versus 1.32 +/- 0.15). These results indicate that increases in circulating AngII levels increase intrarenal angiotensinogen mRNA levels, which may contribute to the sustained renal AngII-generating capacity that paradoxically occurs in AngII-treated hypertensive rats.
循环中血管紧张素II（AngII）水平的长期升高通过多种机制导致持续性高血压和肾内AngII含量增加，这些机制可能包括AngII的持续或增加的局部产生。本研究旨在验证以下假设：长期输注AngII会增加肾血管紧张素原mRNA和蛋白质水平，从而导致肾内AngII水平升高。使用渗透微型泵将AngII（80 ng/分钟）皮下输注到Sprague-Dawley大鼠体内，持续13天。对照大鼠接受假手术。到第12天，AngII处理组大鼠的收缩压升至184±3 mmHg，而假处理组大鼠的收缩压保持在对照水平（125±1 mmHg）。血浆肾素活性明显受到抑制（0.2±0.1对5.3±1.2 ng AngI/ml每小时）；然而，AngII处理组大鼠的肾内AngII含量显著增加（273±29对99±18 fmol/g）。使用多克隆抗血管紧张素原抗体对血浆和肝脏蛋白质进行蛋白质印迹分析，显示出两条特异性免疫反应带，分别在52和64 kD处，而肾组织仅显示一条52 kD的带。光密度分析表明，输注AngII并未改变血浆（52或64 kD）、肾脏（52 kD）或肝脏（52 kD）中的血管紧张素原蛋白质水平；然而，高度糖基化的64 kD血管紧张素原蛋白质的肝脏表达显著增加，几乎增加了四倍（光密度值/对照值比率为3.79±1.16对1.00±0.35）。通过半定量逆转录-PCR检测，AngII处理组大鼠的肾和肝脏血管紧张素原mRNA表达与假处理组大鼠相比显著增加（肾脏，光密度值/甘油醛-3-磷酸脱氢酶mRNA值比率为0.82±0.11对0.58±0.04；肝脏，光密度值/甘油醛-3-磷酸脱氢酶mRNA值比率为2.34±0.07对1.32±0.15）。这些结果表明，循环中AngII水平的升高会增加肾内血管紧张素原mRNA水平，这可能有助于在AngII处理的高血压大鼠中出现的矛盾的持续肾内AngII生成能力。
