不同钙、镁比例饮用水对相对高草酸尿症大鼠肾结石形成及代谢的影响

Effects of calcium and magnesium concentrations in drinking water on renal lithogenesis and metabolism in rats with relative hyperoxaluria

目的探讨低于硬水标准的不同钙、镁比例饮用水对相对高草酸尿症大鼠肾结石形成及代谢的影响。方法 42只雄性Sprague-Dawley大鼠随机分成7组(n=6):空白组、模型组、高钙低镁组、中钙低镁组、低钙低镁组、低钙中镁组和低钙高镁组,空白组饮用纯净水,模型组饮用0.1%乙二醇(EG)配制水,高钙低镁、中钙低镁、低钙低镁、低钙中镁、低钙高镁各干预组在模型组基础上给予不同钙、镁浓度比例的饮用水,浓度比例分别为360/10、120/10、10/10、10/40、10/80(mg/L)。各组大鼠在相同环境下饲养8周后,收集尿液、血液及双肾标本,左肾行H-E染色,光学显微镜观察草酸钙结晶情况;分别测定大鼠24h尿量、尿钙、尿镁、尿草酸、尿枸橼酸排泄量及血钙、血镁、血肌酐以及血尿素氮浓度。结果各组大鼠体质量、摄水量、24h尿量、血钙、血镁和血肌酐等差异无统计学意义。大鼠肾质量低钙低镁组、低钙中镁组均较空白组增加(P<0.05)。低钙中镁组血尿素氮较空白组、模型组升高(P<0.05)。24h尿镁排泄量低钙中镁组较空白组显著增加(P<0.05)。24h尿草酸排泄量模型组、低钙低镁组均高于空白组(P<0.01),中钙低镁组也较空白组显著升高(P<0.05);除低钙低镁组外,其余干预组24h尿草酸排泄量均低于模型组(P<0.01)。各组肾组织病理学检查均未见结晶形成,肾小球、小管细胞大小正常,排列整齐、规则,肾小管管腔无扩张,管腔内无坏死脱落样物质。结论相对高草酸尿症造模对大鼠体内钙和镁的代谢、尿结晶及成石没有影响;在饮用水硬度低于硬水标准下,随钙镁总量(硬度)升高24h尿草酸排泄量减低;单纯高草酸尿症成石草酸浓度或量需要达到一定水平才能显示成石作用;而尿枸橼酸作为结石的保护性因素,它是相对独立的,不受造模及不同钙、镁比例饮用水影响。

Objective To investigate the effects of different calcium and magnesium concentration ratios in drinking water on renal lithogenesis and metabolism in rats with ethylene glycol（EG）-induced relative hyperoxaluria.Methods Normal SD rats were exposed to 0.1% EG and different Ca2＋and Mg2＋concentration ratios（360/10,120/10,10/10,10/40,and 10/80,in mg/L）in drinking water for 8weeks.After the treatments,24 hurine volume and oxalate,citrate,Ca2＋,and Mg2＋levels were measured,and the serum creatinine,blood urea nitrogen（BUN）,Ca2＋,and Mg2＋levels and renal pathologies were examined.Results No significant differences were found among the groups in body weight,water intake,24 hurine volume,24 hurinary citrate excretion,blood Ca2＋and Mg2＋levels,or serum creatinine.Ca/Mg ratios of 10/10 and 10/40 in drinking water caused a significant increase in kidney weight（P〈0.05）,and the latter was associated with significantly increased 24 h urinary Mg2＋excretion as compared with the normal control group（P〈0.05）.BUN was significantly higher in Ca/Mg（10/40）group than in the normal control and model groups（P〈0.05）.The model group and Ca/Mg groups（120/10,10/10and10/40）all showed significantly increased urinary oxalate excretion compared with the normal control group（P〈0.05 or 0.01）;except for Ca/Mg（10/10）group,all the other treatment groups had significantly lower oxalate excretion than the model group（P〈0.01）.None of the groups showed detectable crystal deposition or renal pathologies.Conclusion Relative hyperoxaluria does not affect calcium and magnesium metabolism or the formation of lithogenesis and urinary calcium oxalate crystals in rats.Increased Ca2＋and Mg2＋concentrations that are below the limits in hard water can cause decreased 24 hurinary oxalate excretion.In uncomplicated hyperoxaluria,only a sufficiently high oxalate concentration can lead to lithogenesis.Urinary citrate is not affected by Ca2＋or Mg2＋ratios in drinking water.