Hulter H N, Ilnicki L P, Harbottle J A, Sebastian A
J Lab Clin Med. 1978 Oct;92(4):602-12.
In dogs with chronic hypochloremic metabolic alkalosis associated with ECFV contraction, plasma [HCO-3] ([HCO-3]p) normalizes during expansion of ECFV with a solution containing Cl- and HCO-3 in concentrations duplicating those in the plasma before expansion (isometric expansion). The kidney selectively rejects administered HCO-3 and retains Cl-. If this preferential Cl- less than HCO-3 reabsorptive selectivity were a characteristic renal response to ECFV expansion, isometric expansion during hyperchloremic acidosis would exacerbate the acid-base disturbance rather than correct it as it does in alkalosis. We examined the effect of isometric expansion in dogs with chronic hyperchloremic metabolic acidosis induced by HCl feeding or mineralocorticoid hormone deficiency. During expansion, as the expected decrease occurred in the fractional reabsorption of Na+, a lesser decrease occurred in fractional reabsorption of HCO-3, whereas a greater decrease occurred in fractional reabsorption of Cl-. The kidney selectively retained administered HCO3 and rejected Cl-. [HCO-3]p normalized. The shift to bicarbonate-selective from chloride-selective anion reabsorption during ECFV expansion in metabolic acidosis vs. metabolic alkalosis indicates that in response to ECFV expansion- the kidney selectively alters the ratio of bicarbonate to chloride concentration in the tubular reabsorbate in the direction that tends to normalize plasma acid-base composition, irrespective of the direction of deviation of the initial plasma bicarbonate concentration. The signal that initiates the shift in anion reabsorptive selectivity remains to be identified.
在伴有细胞外液量减少的慢性低氯性代谢性碱中毒犬中，当用含氯离子和碳酸氢根离子且浓度与扩容前血浆中相同的溶液进行细胞外液量扩容（等容扩容）时，血浆[HCO₃⁻]（[HCO₃⁻]p）恢复正常。肾脏选择性地排出血浆中输入的HCO₃⁻并保留Cl⁻。如果这种Cl⁻重吸收选择性低于HCO₃⁻重吸收选择性是肾脏对细胞外液量扩容的特征性反应，那么在高氯性酸中毒时进行等容扩容会加重酸碱紊乱，而不是像在碱中毒时那样纠正酸碱紊乱。我们研究了等容扩容对通过喂食HCl或缺乏盐皮质激素诱导的慢性高氯性代谢性酸中毒犬的影响。在扩容过程中，随着预期的Na⁺分数重吸收减少，HCO₃⁻分数重吸收减少幅度较小，而Cl⁻分数重吸收减少幅度较大。肾脏选择性地保留输入的HCO₃⁻并排出血浆中输入的Cl⁻。[HCO₃⁻]p恢复正常。在代谢性酸中毒与代谢性碱中毒时，细胞外液量扩容过程中阴离子重吸收从对氯离子选择性转变为对碳酸氢根离子选择性，这表明在对细胞外液量扩容的反应中，肾脏会选择性地改变肾小管重吸收液中碳酸氢根离子与氯离子浓度的比例，使其朝着使血浆酸碱组成恢复正常的方向变化，而与初始血浆碳酸氢根离子浓度偏离的方向无关。启动阴离子重吸收选择性转变的信号仍有待确定。
