Bell P D, Navar L G
Kidney Int. 1982 Sep;22(3):234-9. doi: 10.1038/ki.1982.160.
Previous studies have established that during orthograde perfusion from a late proximal tubule site, there is a direct relationship between the magnitude of the feedback response and the level of distal tubular fluid sodium chloride concentration. The present study was conducted in the rat to extend this observation by assessing stop flow pressure (SFP) feedback responses during retrograde perfusion into the early distal tubule with solutions varying in total solute concentration and in the anionic constituent. SFP was measured after blockade of the intermediate proximal and late distal tubular segments with wax. Retrograde perfusion was initiated from an early distal tubular site at 15 nl/min. All solutions contained a 38 mOsm/kg matrix base, and the total solute concentration was increased with either sodium chloride or sodium isethionate to achieve osmolalities of 68, 85, and 120 mOsm/kg. For comparison, feedback responses during perfusion with a 120 mOsm/kg choline chloride solution were evaluated. During perfusion with the 120 mOsm/kg solutions, SFP decreased by 13 +/- 1.3 mm Hg with the sodium chloride solution, 12 +/- 1.5 mm Hg with the sodium isethionate solution, and 12 +/- 1.3 mm Hg with the choline chloride solution. During perfusion with solutions having an osmolality of 85 mOsm/kg, SFP decreased by 8 +/- 1.3 mm Hg with sodium chloride and 8 +/- 0.8 mm Hg with sodium isethionate. The 68 mOsm/kg solutions elicited decreases in SFP of 4.4 +/- 0.4 mm Hg and 5 +/- 0.5 mm Hg. During perfusion with the 38 mOsm/kg matrix solution, SFP decreased by an average of 1.4 +/- 0.9 mm Hg. Linear regression analysis revealed a 1 mm Hg decrease in SFP for every 7.7 mOsm/kg decrease in perfusate osmolality below 120 mOsm/kg. These results confirm previous findings that the magnitude of the feedback response is associated closely with the concentration of the perfusate over a narrow range from 38 to 120 mOsm/kg. Since the responses with sodium isethionate solutions were similar to the responses obtained with sodium chloride containing solutions, these studies provide evidence that the magnitude of the feedback responses are not specifically dependent on alterations in chloride concentration.
以往的研究表明，在从近端肾小管晚期部位进行顺行灌注时，反馈反应的大小与远端肾小管液中氯化钠浓度之间存在直接关系。本研究在大鼠身上进行，通过评估用总溶质浓度和阴离子成分不同的溶液逆行灌注早期远端肾小管时的停流压力（SFP）反馈反应，来扩展这一观察结果。在用蜡阻塞近端肾小管中段和远端肾小管晚期段后测量SFP。从早期远端肾小管部位以15 nl/min的速度开始逆行灌注。所有溶液均含有38 mOsm/kg的基质碱，总溶质浓度通过添加氯化钠或羟乙基磺酸钠来提高，以达到68、85和120 mOsm/kg的渗透压。为作比较，评估了用120 mOsm/kg氯化胆碱溶液灌注时的反馈反应。在用120 mOsm/kg溶液灌注期间，用氯化钠溶液时SFP降低了13±1.3 mmHg，用羟乙基磺酸钠溶液时降低了12±1.5 mmHg，用氯化胆碱溶液时降低了12±1.3 mmHg。在用渗透压为85 mOsm/kg的溶液灌注期间，用氯化钠时SFP降低了8±1.3 mmHg，用羟乙基磺酸钠时降低了8±0.8 mmHg。68 mOsm/kg的溶液使SFP分别降低了4.4±0.4 mmHg和5±0.5 mmHg。在用38 mOsm/kg基质溶液灌注期间，SFP平均降低了1.4±0.9 mmHg。线性回归分析显示，当灌注液渗透压低于120 mOsm/kg时，每降低7.7 mOsm/kg，SFP降低1 mmHg。这些结果证实了先前的发现，即在38至120 mOsm/kg的狭窄范围内，反馈反应的大小与灌注液浓度密切相关。由于用羟乙基磺酸钠溶液得到的反应与用含氯化钠溶液得到的反应相似，这些研究提供了证据，表明反馈反应的大小并非特别依赖于氯离子浓度的改变。
