Thomson S, Vallon V, Blantz R C
Department of Medicine, University of California San Diego, USA.
Am J Physiol. 1996 Dec;271(6 Pt 2):F1123-30. doi: 10.1152/ajprenal.1996.271.6.F1123.
The contribution of preglomerular resistance changes to the tubuloglomerular feedback (TGF) effector response was evaluated by micropuncture in hydropenic rats. Studies were performed in free-flowing nephrons to compare the fractional compensation (C) for perturbations in late proximal flow (VLP) with associated changes in glomerular capillary hydrostatic pressure (PGC). VLP was monitored by a noninvasive optical technique, and PGC was monitored by direct capillary micropuncture. Data were employed in conjunction with a model of glomerular filtration to analyze the TGF effector mechanism. C varied with the applied perturbation (VH), showing a single peak near the natural operating point. In contrast, the effect of TGF on PGC was asymmetric about the operating point, such that PGC was sensitive only to large positive perturbations. The model predicts that changes in preglomerular resistance account for only a small fraction of the integrated TGF response to small disturbances in the ambient state of the nephron but account for a greater share of the response to larger increments in flow. The TGF response in hydropenic rats is mediated by both pre- and postglomerular vascular elements.
通过对禁水大鼠进行微穿刺，评估了球前阻力变化对肾小管-肾小球反馈（TGF）效应器反应的贡献。在自由流动的肾单位中进行研究，以比较近端晚期流量（VLP）扰动的分数补偿（C）与肾小球毛细血管静水压（PGC）的相关变化。VLP通过无创光学技术监测，PGC通过直接毛细血管微穿刺监测。数据与肾小球滤过模型结合使用，以分析TGF效应器机制。C随施加的扰动（VH）而变化，在自然工作点附近出现一个单峰。相比之下，TGF对PGC的影响在工作点两侧不对称，使得PGC仅对大的正扰动敏感。该模型预测，球前阻力的变化仅占肾单位环境状态小扰动的综合TGF反应的一小部分，但占流量较大增量反应的更大份额。禁水大鼠的TGF反应由球前和球后血管元件介导。
