Cheung P K, Klok P A, Baller J F, Bakker W W
Department of Pathology and Laboratorium Medicine, University of Groningen, The Netherlands.
Kidney Int. 2000 Apr;57(4):1512-20. doi: 10.1046/j.1523-1755.2000.00996.x.
The human plasma constituent hemopexin (Hx), following incubation with renal tissue, is able to induce glomerular alterations in vitro that are similar to those seen in minimal change disease (MCD). Whether this acute phase reactant is also able to induce proteinuria and minimal change-like alterations in vivo is questioned.
In the first set of experiments, Hx (4.0 mg in 5.0 mL saline) or equal amounts of control fraction, that is, heat-inactivated Hx (HI-Hx), were infused into conscious rats (N = 6) that had been surgically equipped with a cannula inserted into the suprarenal artery (SRA), enabling direct contact of the infusate and the renal microvasculature. Each animal received HI-Hx at day 1 for 15 minutes (flow rate 20.0 mL/h), subsequently followed by saline for seven hours (Flow rate 5.0 mL/h), after which the cannula was disconnected. At day 2, identical infusions in the same rat were carried out, using native Hx. Urine samples collected every 30 minutes during the experiments were monitored for protein content using standard methods. In the second set of experiments, unilateral perfusion was done ex vivo in anesthetized rats with Hx (N = 5) or HI-Hx (N = 3; 1.5 mg/mL; 4.0 mL during 6 min). After reconnection of the circulation, urine samples of both kidneys were collected every 30 minutes during five hours via ureter cannulation. Urinary protein (expressed as the difference in excretion between perfused and nonperfused kidney) was calculated in mg/24 h. In additional experiments, rats were sacrificed two hours after perfusion of Hx or heat-inactivated (control) Hx (first set of experiments) or after five hours (second set of experiments), and kidneys were processed for immunohistochemical and ultrastructural examination.
The results of experiment 1 show a significant increase of proteinuria after Hx infusion versus HI-Hx (means +/- SD, 41.91 +/- 16.01 mg/24 h vs. control, 21.22 +/- 5.69 mg/24 h; P </= 0.03). Histochemical and electron microscopical examination of kidney tissue fragments taken at the time of proteinuria showed diminished expression of glomerular ecto-ATPase and enhanced effacement of epithelial foot processes at the ultrastructural level. In the second set of experiments, the results show significant urinary protein excretion peaking one hour after perfusion (6.63 +/- 7.06 mg/24 h), exclusively in Hx-perfused animals (analysis of variance, P < or = 0.001).
It is concluded that Hx is able to induce proteinuria associated with MCD-like alterations in rat kidney in vivo.
人血浆成分血红素结合蛋白（Hx）与肾组织孵育后，能够在体外诱导出类似于微小病变肾病（MCD）所见的肾小球改变。这种急性期反应物是否也能在体内诱导蛋白尿和微小病变样改变受到质疑。
在第一组实验中，将Hx（4.0mg溶于5.0mL盐水中）或等量的对照组分，即热灭活的Hx（HI - Hx），注入已通过手术在肾上腺动脉（SRA）插入套管的清醒大鼠（N = 6）体内，使注入物与肾微血管直接接触。每只动物在第1天接受15分钟的HI - Hx输注（流速20.0mL/h），随后用盐水输注7小时（流速5.0mL/h），之后断开套管。在第2天，对同一只大鼠进行相同的输注，使用天然Hx。实验期间每30分钟收集的尿液样本用标准方法监测蛋白质含量。在第二组实验中，对麻醉的大鼠进行离体单侧灌注，分别灌注Hx（N = 5）或HI - Hx（N = 3；1.5mg/mL；6分钟内灌注4.0mL）。循环重新连接后，通过输尿管插管在5小时内每30分钟收集双侧肾脏的尿液样本。计算尿蛋白（表示为灌注肾与未灌注肾排泄量的差值），单位为mg/24h。在另外的实验中，大鼠在灌注Hx或热灭活（对照）Hx后2小时（第一组实验）或5小时（第二组实验）处死，肾脏进行免疫组织化学和超微结构检查。
实验1的结果显示，与HI - Hx相比，输注Hx后蛋白尿显著增加（平均值±标准差：41.91±16.01mg/24h对对照组21.22±5.69mg/24h；P≤0.03）。蛋白尿时采集的肾组织碎片的组织化学和电子显微镜检查显示，肾小球外ATP酶表达减少，超微结构水平上皮足突消失增强。在第二组实验中，结果显示仅在灌注Hx的动物中，灌注后1小时尿蛋白排泄显著增加并达到峰值（6.63±7.06mg/24h）（方差分析，P≤0.001）。
得出结论，Hx能够在大鼠肾脏中诱导与MCD样改变相关的蛋白尿。
