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

Abstract

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(P0.05),and the latter was associated with significantly increased 24 h urinary Mg2+excretion as compared with the normal control group(P0.05).BUN was significantly higher in Ca/Mg(10/40)group than in the normal control and model groups(P0.05).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(P0.05 or 0.01);except for Ca/Mg(10/10)group,all the other treatment groups had significantly lower oxalate excretion than the model group(P0.01).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.