Moore L C, Mason J
Am J Physiol. 1986 Jun;250(6 Pt 2):F1024-32. doi: 10.1152/ajprenal.1986.250.6.F1024.
A closed-feedback loop micropuncture method was used to examine tubuloglomerular feedback (TGF) and the regulation of distal fluid delivery in hydropenic rats (CON), moderately hemorrhaged rats (HEM), and rats given desoxycorticosterone (DOC) and 0.6% saline to drink. Distal delivery and TGF response curves were measured with four samples per nephron: a spontaneous early distal collection, two distal collections during moderate (7.5 nl/min) and saturating (30 nl/min) perturbations in nephron fluid load, and a proximal collection to measure single-nephron glomerular filtration rate (SNGFR) during TGF inhibition. Arterial pressure, predistal volume reabsorption, SNGFR, and early distal flow were significantly higher in DOC than in HEM; the CON group exhibited intermediate values. Except for a greater maximum TGF response in HEM, the normalized TGF responses were similar in all three groups, as was the regulation of distal fluid delivery. However, the TGF onset threshold and the TGF operating point, defined by the spontaneous rates of early distal flow and SNGFR, were reset such that distal fluid delivery and SNGFR were higher in DOC than in HEM, as was renal sodium excretion. The results show that the level around which TGF stabilizes distal fluid delivery is reset when extracellular fluid volume is altered.
采用封闭反馈回路微穿刺法，研究禁水大鼠（CON）、中度出血大鼠（HEM）以及给予脱氧皮质酮（DOC）并饮用0.6%盐水的大鼠的球管反馈（TGF）及远端液体输送调节。每个肾单位取4个样本测量远端输送和TGF反应曲线：一个自发早期远端收集样本，在肾单位液体负荷中度（7.5 nl/min）和饱和（30 nl/min）扰动期间的两个远端收集样本，以及一个近端收集样本以测量TGF抑制期间的单肾单位肾小球滤过率（SNGFR）。DOC组的动脉压、远端前体积重吸收、SNGFR和早期远端流量显著高于HEM组；CON组呈现中间值。除了HEM组的最大TGF反应更大外，三组的标准化TGF反应相似，远端液体输送调节也相似。然而，由早期远端流量和SNGFR的自发速率定义的TGF起始阈值和TGF工作点被重置，使得DOC组的远端液体输送和SNGFR高于HEM组，肾钠排泄也是如此。结果表明，当细胞外液体积改变时，TGF稳定远端液体输送的水平会被重置。
