Maron M B, Lang S A
Department of Physiology, Northeastern Ohio Universities College of Medicine, Rootstown 44272.
Microvasc Res. 1992 Jan;43(1):60-72. doi: 10.1016/0026-2862(92)90006-b.
We determined whether the solvent drag reflection coefficient (sigma f) for total proteins of a canine perfused left lower lung lobe (LLL) preparation decreases at elevated venous pressures (Pv). We found that sigma f (estimated using the hematocrit-protein technique) remained constant at all Pv's (30-95 mm Hg) evaluated. These results were unanticipated, since previous studies reported increases in protein permeability at Pv's within this range. We conducted two additional studies to better understand the basis for these observations. In the first, we evaluated the effect of high Pv (85 mm Hg) on sigma f of a canine perfused forelimb preparation and found sigma f to be reduced. This difference in response suggests that the normal sigma f's observed in the LLL were not due to high Pv per se, but rather that there is some intrinsic difference between the pulmonary and the systemic circulations that accounts for the difference. The second study was designed to determine whether the normal sigma f's observed in the LLL at high Pv's provide meaningful information about pulmonary vascular endothelial permeability. We damaged LLL's with alloxan, oleic acid, or HCl and obtained near normal estimates of sigma f at high Pv. These results indicated that it is not possible to easily distinguish between a normal and a damaged pulmonary vasculature when sigma f is measured at high Pv. We suggest that the normal estimates of sigma f obtained at high Pv in the LLL results from an increased fraction of the transvascular flow occurring through pathways that exclude macromolecules.
我们研究了犬左下肺叶（LLL）灌注标本中总蛋白的溶剂拖曳反射系数（σf）在静脉压（Pv）升高时是否降低。我们发现，（使用血细胞比容-蛋白技术估算的）σf在所有评估的Pv值（30 - 95 mmHg）下均保持恒定。这些结果出乎意料，因为先前的研究报道在此范围内的Pv值时蛋白质通透性会增加。我们又进行了两项额外的研究，以更好地理解这些观察结果的依据。在第一项研究中，我们评估了高Pv（85 mmHg）对犬前肢灌注标本σf的影响，发现σf降低。这种反应差异表明，在LLL中观察到的正常σf并非源于高Pv本身，而是肺循环和体循环之间存在一些内在差异导致了这种差异。第二项研究旨在确定在高Pv下LLL中观察到的正常σf是否能提供有关肺血管内皮通透性的有意义信息。我们用四氧嘧啶、油酸或盐酸损伤LLL，并在高Pv下获得了接近正常的σf估算值。这些结果表明，当在高Pv下测量σf时，很难区分正常和受损的肺血管。我们认为，在LLL中高Pv下获得的正常σf估算值是由于通过排除大分子的途径发生的跨血管流量比例增加所致。
