Kirchner K A, Galla J H, Luke R G
Am J Physiol. 1980 Dec;239(6):F552-9. doi: 10.1152/ajprenal.1980.239.6.F552.
To study factors influencing Cl reabsorption in the collecting duct segment of the rat, excretion of Cl and of 36Cl injected into late distal tubule segments of superficial nephrons were examined by microinjection and free-flow micropuncture techniques. Selective dietary Cl restriction for 7-10 days decreased urinary 36Cl recovery for microinjection [74 +/- 5% (SE)] compared with normal rats (90 +/- 3%, P < 0.01). Infusion of 0.15 M NaHCO3 (10% body wt) in the Cl-restricted rat led to marked increases in urinary flow rates and sodium excretion but did not increase 36Cl recovery. In these NaHCO3-infused rats, recovery of 36Cl was unaffected by increasing Cl concentration in the injectate from 40 to 140 peq/nl, but increased to levels not different from control (89 +/- 3%) when amphotericin B was included in the injectate. Equivalent infusion of 0.15 M NaCl in the Cl-restricted rats also increased 36Cl recovery to control levels (89 +/- 3%). This response was not altered by administration of DOCA. Absolute chloride delivery to late distal tubule sites was not different in NaCl- and NaHCO3-expanded groups, and (TF/UF)Cl was less in the NaHCO3 group (0.27 +/- 0.03 vs. 0.37 +/- 0.02, P < 0.05); therefore, the chemical gradient for Cl did not favor Cl efflux. There was a significant correlation between urinary recovery of 36Cl and urinary Cl excretion in the NaCl- and NaHCO3-expanded animals. It is suggested that Cl restriction alters, by an as yet unknown mechanism that is independent of changes in Na balance, the intrinsic Cl-absorbing capacity of the collecting duct.
为研究影响大鼠集合管段氯重吸收的因素，采用微量注射和自由流微量穿刺技术，检测了注入浅表肾单位远曲小管晚期段的氯及³⁶Cl的排泄情况。与正常大鼠相比，选择性限氯饮食7 - 10天可使微量注射的尿³⁶Cl回收率降低[74±5%（标准误）]（正常大鼠为90±3%，P<0.01）。给限氯大鼠输注0.15M NaHCO₃（体重的10%）可使尿流率和钠排泄显著增加，但³⁶Cl回收率未增加。在这些输注NaHCO₃的大鼠中，当注入液中氯浓度从40增加到140皮摩尔/纳升时，³⁶Cl回收率未受影响，但当注入液中加入两性霉素B时，³⁶Cl回收率增加至与对照组无差异的水平（89±3%）。给限氯大鼠等量输注0.15M NaCl也可使³⁶Cl回收率增加至对照水平（89±3%）。给予去氧皮质酮醋酸酯（DOCA）并未改变这种反应。NaCl和NaHCO₃扩容组输送至远曲小管晚期部位的绝对氯量无差异，且NaHCO₃组的（管液/超滤）氯较低（0.27±0.03对0.37±0.02，P<0.05）；因此，氯的化学梯度不利于氯外流。在NaCl和NaHCO₃扩容的动物中，尿³⁶Cl回收率与尿氯排泄之间存在显著相关性。提示限氯通过一种尚未明确的、独立于钠平衡变化的机制，改变了集合管的固有氯吸收能力。
