Clausen G, Tyssebotn I, Kirkebø A, Ofjord E S, Aukland K
Acta Physiol Scand. 1981 Dec;113(4):471-9. doi: 10.1111/j.1748-1716.1981.tb06924.x.
Recent studies indicate that intrarenal distribution of blood flow measured with microspheres (Ms) during control conditions depends on Ms size. We therefore compared local flow in outer and middle cortex (C1 and C2) and inner cortex plus the medulla (C3M) using 10.5-12.0 and 13.9-15.0 mum Ms (Ms 10 and Ms 15). One pair of Ms 10 and Ms 15 was injected during control and a second pair at 80% increased or 50% decreased total renal vascular conductance (RVC), as induced by infusion of acetylcholine (Ach) and angiotensin II (Ang) or noradrenaline (NA). All zones participated in dilation and constriction, as indicated by both Ms sizes. Ms 15 underestimated C3M flow as compared to Ms 10, by 19% during control or Ang, and by 3% during Ach (P less than 0.02). The C3M flow fractions increased during Ach and decreased during Ang, whereas NA gave greatly variable results, on average no change. Renal Ms extraction averaged 97.0 +/- 3% for Ms 10, 98.6 +/- 2.4% (S.D.) for Ms 15. About 8% of Ms 10 and less than 1% of Ms 15 were located in peritubular capillaries in each cortical zone. Neither total Ms extraction nor zonal extraglomerular Ms fraction changed over the present RVC range. Thus, the Ms 10 to Ms 15 differences as well as the observed redistribution must be due to differences in local entry of Ms into the afferent arterioles. However, steric restriction of Ms at arteriolar inlets did not play a significant role. The measured redistribution of fractional flow could in part be due to skimming of Ms at arteriolar inlets along the interlobular arteries (i.l.a.), depending on the C3M flow fraction, Ms size and i.l.a. diameter. If the observed fractional flow redistributions were solely due to variable Ms skimming, Ms 15 underestimated C3M flow by 53%, Ms 10 by 43%, during Ang as compared to Ach. Although Ms 10 and Ms 15 may correctly indicate the direction of fractional glomerular flow redistribution, at least Ms 15 overestimates this phenomenon quantitatively.
近期研究表明，在对照条件下，用微球（Ms）测量的肾内血流分布取决于微球大小。因此，我们使用10.5 - 12.0微米和13.9 - 15.0微米的微球（Ms 10和Ms 15）比较了外皮质和中皮质（C1和C2）以及内皮质加髓质（C3M）的局部血流。在对照期间注射一对Ms 10和Ms 15，在通过输注乙酰胆碱（Ach）、血管紧张素II（Ang）或去甲肾上腺素（NA）使总肾血管电导（RVC）增加80%或降低50%时注射第二对。两种微球大小的数据均表明，所有区域均参与了血管舒张和收缩。与Ms 10相比，Ms 15低估了C3M血流，在对照或Ang作用期间低估了19%，在Ach作用期间低估了3%（P < 0.02）。C3M血流分数在Ach作用期间增加，在Ang作用期间降低，而NA的结果变化很大，平均无变化。Ms 10的肾内微球摄取平均为97.0±3%，Ms 15为98.6±2.4%（标准差）。在每个皮质区域，约8%的Ms 10和不到1%的Ms 15位于肾小管周围毛细血管中。在当前的RVC范围内，总微球摄取量和区域肾小球外微球分数均未发生变化。因此，Ms 10与Ms 15之间的差异以及观察到的血流重新分布必定是由于微球进入入球小动脉的局部差异所致。然而，微球在小动脉入口处的空间限制并未起显著作用。测量到的血流分数重新分布部分可能是由于微球沿小叶间动脉（i.l.a.）在小动脉入口处的掠过，这取决于C3M血流分数、微球大小和i.l.a.直径。如果观察到的血流分数重新分布完全是由于微球掠过的变化所致，那么在Ang作用期间与Ach相比，Ms 15低估C3M血流53%，Ms 10低估43%。尽管Ms 10和Ms 15可能正确地指示了肾小球血流分数重新分布的方向，但至少Ms 15在定量方面高估了这一现象。
