Mercier O, Prigent A, Bichara M, Paillard M, Leviel F
Am J Physiol. 1986 Mar;250(3 Pt 2):F441-50. doi: 10.1152/ajprenal.1986.250.3.F441.
Recollection micropuncture experiments were carried out in thyroparathyroidectomized volume-expanded rats to examine the effects of CaCl2 infusion on the renal and nephronal segmental handling of chloride and bicarbonate. In group 1A, a 0.23 mM increase in plasma calcium concentration [delta(Ca)P] reduced urinary total CO2 (tCO2) excretion from 401 +/- 90 to 166 +/- 43 nmol X min-1 X g kidney wt-1 (P less than 0.05), whereas tCO2 filtered load was slightly diminished from 34,086 +/- 3,627 to 28,904 +/- 2,496 nmol X min-1 X g kidney wt-1 (NS). In group 1B [delta(Ca)P, 0.73 mM], whole kidney filtered loads were significantly lowered, as was urinary tCO2 excretion; however, urinary excretion of sodium, chloride, and water remained constant. Calcium infusion inhibited the proximal reabsorption of chloride 25% and water 16%; however, calcium infusion caused the end-proximal tCO2 concentration to significantly decrease so that the absolute and fractional tCO2 reabsorption remained constant. In group 2 [delta(Ca)P, 0.43 mM], whole kidney filtered load was unchanged for chloride and water but decreased for bicarbonate; urinary tCO2 excretion was reduced, whereas chloride and water excretion increased. In this group, early distal micropunctures evidenced that superficial single-nephron filtered loads were significantly reduced during calcium infusion; early distal chloride delivery was enhanced from 348 +/- 32 to 441 +/- 36 pmol X min-1 X g kidney wt-1 (P less than 0.05), whereas tCO2 delivery decreased from 47 +/- 5 to 38 +/- 4 pmol X min-1 X g kidney wt-1 (P less than 0.05). In group 3 of time control animals, whole kidney and early distal data were unchanged during second period. In group 4, H+ secretion in the collecting duct, as assessed by analyzing the relationship between urine-minus-blood PCO2 and urinary bicarbonate concentration in maximally alkaline urine, was not modified during CaCl2 infusion [delta(Ca)P, 0.79 mM]. We conclude that increase in plasma calcium concentration inhibits proximal NaCl and water reabsorption, whereas it stimulates the bicarbonate transport relative to that of chloride, leading to an enhanced proximal and renal bicarbonate-to-chloride reabsorptive ratio that could generate metabolic alkalosis; and decreases urinary bicarbonate excretion by also lowering the bicarbonate filtered load.
在甲状腺甲状旁腺切除且血容量扩张的大鼠中进行了回收微穿刺实验，以研究输注氯化钙对肾脏及肾单位各节段对氯离子和碳酸氢根的处理作用。在1A组中，血浆钙浓度升高0.23 mM [Δ(Ca)P]，使尿中总二氧化碳（tCO2）排泄量从401±90降至166±43 nmol·min-1·g肾重-1（P<0.05），而tCO2滤过负荷仅略有降低，从34,086±3,627降至28,904±2,496 nmol·min-1·g肾重-1（无统计学差异）。在1B组[Δ(Ca)P，0.73 mM]中，全肾滤过负荷显著降低，尿tCO2排泄量也降低；然而，钠、氯和水的尿排泄量保持不变。输注钙抑制近端氯离子重吸收25%和水重吸收16%；然而，输注钙使近端终末tCO2浓度显著降低，因此tCO2的绝对重吸收量和重吸收分数保持不变。在2组[Δ(Ca)P，0.43 mM]中，全肾对氯和水的滤过负荷不变，但对碳酸氢根的滤过负荷降低；尿tCO2排泄量减少，而氯和水的排泄量增加。在该组中，早期远曲小管微穿刺显示，输注钙期间浅表单肾单位滤过负荷显著降低；早期远曲小管氯离子输送量从348±32增加至441±36 pmol·min-1·g肾重-1（P<0.05），而tCO2输送量从47±5降至38±4 pmol·min-1·g肾重-1（P<0.05）。在3组时间对照动物中，第二阶段全肾和早期远曲小管的数据未发生变化。在4组中，通过分析最大碱性尿中尿-血PCO2与尿碳酸氢根浓度之间的关系评估，在输注氯化钙[Δ(Ca)P，0.79 mM]期间，集合管中的H+分泌未发生改变。我们得出结论，血浆钙浓度升高抑制近端NaCl和水的重吸收，而相对于氯离子，它刺激碳酸氢根转运，导致近端及全肾碳酸氢根与氯离子重吸收比值升高，这可能导致代谢性碱中毒；并且通过降低碳酸氢根滤过负荷也减少了尿中碳酸氢根的排泄。
