Brown S A
Department of Physiology and Pharmacology, College of Veterinary Medicine, University of Georgia, Athens 30602.
Am J Vet Res. 1993 Jun;54(6):970-5.
To investigate the determinants of glomerular ultrafiltration, renal micropuncture studies were performed in 9 cats. Mean single nephron glomerular filtration rate (SNGFR), directly measured in outer cortical nephrons, was 29.4 +/- 3.0 nl/min. This was similar to the estimated value for SNGFR (31.3 +/- 4.6 nl/min) obtained by dividing left kidney total glomerular filtration rate (1.41 +/- 0.12 ml/min/kg of body weight) by left glomerular count (175,200 +/- 13,600 glomeruli/kidney). In micropuncture studies performed at mean renal perfusion pressure of 101.3 +/- 1.0 mm of Hg, the glomerular capillary hydrostatic pressure was 58.0 +/- 1.4 mm of Hg. The glomerular transcapillary hydrostatic pressure gradient (40.0 +/- 1.8 mm of Hg) exceeded colloid osmotic pressure at the efferent end of the glomerular capillaries (28.4 +/- 2.1 mm of Hg) in all cats studied, indicating existence of positive effective filtration pressure throughout the glomerular capillary bed. These results indicate that glomerular capillary pressure is sufficiently high to prevent forces from reaching filtration pressure equilibrium in feline outer cortical nephrons. Thus, the value of SNGFR in feline nephrons depends on the glomerular transcapillary hydrostatic pressure gradient and the glomerular ultrafiltration coefficient.
为了研究肾小球超滤的决定因素，对9只猫进行了肾脏微穿刺研究。在外皮质肾单位中直接测量的平均单肾单位肾小球滤过率（SNGFR）为29.4±3.0 nl/分钟。这与通过将左肾总肾小球滤过率（1.41±0.12 ml/分钟/千克体重）除以左肾小球数量（175,200±13,600个肾小球/肾脏）获得的SNGFR估计值（31.3±4.6 nl/分钟）相似。在平均肾灌注压为101.3±1.0 mmHg的微穿刺研究中，肾小球毛细血管静水压为58.0±1.4 mmHg。在所有研究的猫中，肾小球跨毛细血管静水压梯度（40.0±1.8 mmHg）超过了肾小球毛细血管出球端的胶体渗透压（28.4±2.1 mmHg），表明在整个肾小球毛细血管床中存在正的有效滤过压。这些结果表明，在猫的外皮质肾单位中，肾小球毛细血管压力足够高，以防止各种力量达到滤过压力平衡。因此，猫肾单位中SNGFR的值取决于肾小球跨毛细血管静水压梯度和肾小球超滤系数。
