Effros R M, Schapira R, Presberg K, Ozker K, Jacobs E R
Division of Pulmonary and Critical Care Medicine, Department of Medicine, Medical College of Wisconsin, Milwaukee 53226; and Zablocki Veterans Affairs Medical Center, Milwaukee, Wisconsin 53295-1000, USA.
J Appl Physiol (1985). 1998 Sep;85(3):986-92. doi: 10.1152/jappl.1998.85.3.986.
Stop-flow studies were used to characterize solute uptake in isolated rat lungs. These lungs were perfused at 8 or 34 ml/min for 10-28 s with solutions containing 125I-albumin and two or more of the following diffusible indicators: [3H]mannitol, [14C]urea, 3HOH, 201Tl+, or 86Rb+. After this loading period, flow was stopped for 10-300 s and then resumed to flush out the perfusate that remained in the pulmonary vasculature during the stop interval. Concentrations of 201Tl+ and 86Rb+ in the venous outflow decreased after the stop interval, indicating uptake from exchange vessels during the stop interval. The amount of these K+ analogs lost from the circulation during the stop interval was greater when the intervals were longer. However, losses of 201T1+ at 90 s approached those at 300 s. Because extraction continued after the vasculature had been flushed, vascular levels had presumably fallen to negligible levels during the stop interval. By 90 s of stop flow the vascular volume that was cleared of 201T1+ averaged 0.657 +/- 0.034 (SE) ml in the experiments perfused at 8 ml/min and 0.629 +/- 0.108 ml in those perfused at 34 ml/min. Increases in perfusate K+ decreased the cleared volumes of 201T1+ and 86Rb+. Uptake of [3H]mannitol, [14C]urea, and 3HOH during the stop intervals was observed only when the lungs were loaded at high flow for short intervals. Decreases in 201T1+ and 86Rb+ concentrations in the pulmonary outflow can be used to identify the fraction of the collected samples that were within exchange vessels of the lung during the stop interval and may help determine the distribution of solute and water exchange along the pulmonary vasculature.
采用停流研究来表征分离的大鼠肺脏对溶质的摄取。这些肺脏以8或34毫升/分钟的流速灌注含125I-白蛋白以及以下两种或更多种可扩散指示剂的溶液10 - 28秒：[3H]甘露醇、[14C]尿素、3HOH、201Tl +或86Rb +。在这个加载期之后，停流10 - 300秒，然后恢复流动以冲洗出停流间隔期间残留在肺血管系统中的灌注液。停流间隔后，静脉流出液中201Tl +和86Rb +的浓度降低，表明在停流间隔期间从交换血管摄取。当间隔时间更长时，这些钾类似物在停流间隔期间从循环中损失的量更大。然而，90秒时201T1 +的损失接近300秒时的损失。因为在血管系统被冲洗后摄取仍在继续，所以在停流间隔期间血管内水平大概已降至可忽略不计的水平。在以8毫升/分钟灌注的实验中，到停流90秒时，清除201T1 +的血管容积平均为0.657±0.034（标准误）毫升，在以34毫升/分钟灌注的实验中为0.629±0.108毫升。灌注液中钾的增加会降低201T1 +和86Rb +的清除容积。仅当肺脏在短时间内以高流速加载时，才观察到停流间隔期间[3H]甘露醇、[14C]尿素和3HOH的摄取。肺流出液中201T1 +和86Rb +浓度的降低可用于确定停流间隔期间收集的样本中处于肺交换血管内的部分，并可能有助于确定溶质和水沿肺血管系统的交换分布。
