Canzanello V J, Bodvarsson M, Kraut J A, Johns C A, Slatopolsky E, Madias N E
Department of Medicine, Tufts University School of Medicine, Boston, Massachusetts.
Kidney Int. 1990 Sep;38(3):409-16. doi: 10.1038/ki.1990.220.
It is currently believed that the two chronic acidemic disorders exert disparate effects on urinary calcium excretion: chronic metabolic acidosis induces consistent hypercalciuria, but no appreciable change or even a decrease in calcium excretion is reported to attend chronic respiratory acidosis. Whereas the effect of metabolic acidosis is well documented, little work has been carried out in chronic hypercapnia. In fact, most of the studies on chronic respiratory acidosis were short in duration, had employed only mild hypercapnia, or had failed to control carefully the prevailing metabolic conditions. We have carried out balance observations in nine dogs exposed to a 10% CO2 atmosphere in an environmental chamber for a period of two weeks. Chronic respiratory acidosis led to a significant increase in urinary calcium excretion from a mean control value of 0.4 +/- 0.1 mmol/day to 0.6 +/- 0.1 mmol/day during both week 1 and 2 of hypercapnia (P less than 0.05). Hypercalciuria occurred even though filtered load of calcium fell. Mean fractional excretion of calcium increased significantly during each week of hypercapnia averaging 0.60 +/- 0.12% during control, 1.05 +/- 0.13% during week 1, and 1.26 +/- 0.17% during week 2 of hypercapnic exposure (P less than 0.05). There were no changes in plasma levels of immunoreactive parathyroid hormone or 1,25-dihydroxyvitamin D3. These findings suggest that chronic respiratory acidosis, just like chronic metabolic acidosis, augments urinary calcium excretion by a direct depressive effect on the tubular reabsorption of calcium.
目前认为，这两种慢性酸血症对尿钙排泄有不同影响：慢性代谢性酸中毒会导致持续性高钙尿症，但据报道，慢性呼吸性酸中毒时钙排泄无明显变化甚至减少。虽然代谢性酸中毒的影响已有充分记录，但关于慢性高碳酸血症的研究较少。事实上，大多数关于慢性呼吸性酸中毒的研究持续时间较短，仅采用轻度高碳酸血症，或未能仔细控制当时的代谢状况。我们对9只狗进行了平衡观察，将它们置于环境舱中，使其暴露于10%二氧化碳的环境中两周。慢性呼吸性酸中毒导致尿钙排泄显著增加，在高碳酸血症的第1周和第2周，尿钙排泄量从平均对照值0.4±0.1 mmol/天增加到0.6±0.1 mmol/天（P<0.05）。即使钙滤过负荷下降，仍出现高钙尿症。在高碳酸血症的每一周，钙的平均分数排泄率均显著增加，对照期平均为0.60±0.12%，高碳酸血症暴露第1周为1.05±0.13%，第2周为1.26±0.17%（P<0.05）。免疫反应性甲状旁腺激素或1,25-二羟维生素D3的血浆水平无变化。这些发现表明，慢性呼吸性酸中毒与慢性代谢性酸中毒一样，通过对肾小管钙重吸收的直接抑制作用增加尿钙排泄。
