Griffith T M, Edwards D H
Department of Diagnostic Radiology, University of Wales College of Medicine, Heath Park, Cardiff, United Kingdom.
Am J Physiol. 1990 Apr;258(4 Pt 2):H1171-80. doi: 10.1152/ajpheart.1990.258.4.H1171.
The influence of basal endothelium-derived relaxing factor (EDRF) activity on autoregulation was studied under conditions of controlled-flow and controlled-pressure perfusion in the isolated rabbit ear, a weakly autoregulating vascular bed. Hemoglobin and NG-monomethyl-L-arginine were used to inhibit EDRF activity, and in some experiments resting tone was increased by serotonin. The diameters of five generations of resistance arteries (ranging from 70 to 1,000 microns in size) were measured at different flow rates by X-ray microangiography. Diameter-flow (D-Q) relationships were correlated with pressure-flow (P-Q) and conductance-flow (G-Q) relationships. In the presence of EDRF activity no autoregulation was observed, P-Q relationships being linear and G-Q and D-Q relationships common both to controlled-flow and to controlled-pressure modes of perfusion. After inhibition of EDRF activity in constricted preparations, P-Q relationships became sigmoidal in shape in controlled-pressure perfusion mode, reflecting a range of perfusion pressures/flow rates over which they were able to "autoregulate" flow. Over this autoregulatory range the corresponding G-Q and D-Q relationships exhibited regions of negative slope. Autoregulation was not observed in controlled-flow perfusion mode even in the absence of EDRF activity. The findings imply that flow- or pressure-dependent constriction can mediate autoregulation in controlled-pressure mode when not overridden by basal EDRF activity, as normally appears to be the case in these preparations. Differences in autoregulation in different organs may be inversely related to EDRF activity, which is known to differ between vascular beds.
在分离的兔耳（一种自身调节能力较弱的血管床）中，在控制流量和控制压力灌注条件下，研究了基础内皮衍生舒张因子（EDRF）活性对自身调节的影响。使用血红蛋白和NG-单甲基-L-精氨酸抑制EDRF活性，并且在一些实验中用血清素增加静息张力。通过X射线微血管造影术在不同流速下测量了五代阻力动脉（直径范围为70至1000微米）的直径。直径-流量（D-Q）关系与压力-流量（P-Q）和电导-流量（G-Q）关系相关。在存在EDRF活性的情况下，未观察到自身调节，P-Q关系呈线性，并且G-Q和D-Q关系在控制流量和控制压力灌注模式中均常见。在收缩制剂中抑制EDRF活性后，在控制压力灌注模式下P-Q关系变为S形，反映了一系列灌注压力/流速，在该范围内它们能够“自身调节”流量。在这个自身调节范围内，相应的G-Q和D-Q关系呈现负斜率区域。即使在没有EDRF活性的情况下，在控制流量灌注模式中也未观察到自身调节。这些发现表明，当不受基础EDRF活性（在这些制剂中通常似乎是这种情况）的影响时，流量或压力依赖性收缩可以在控制压力模式中介导自身调节。不同器官中自身调节的差异可能与EDRF活性呈负相关，已知EDRF活性在不同血管床之间存在差异。
