Ichikawa I, Purkerson M L, Klahr S, Troy J L, Martinez-Maldonado M, Brenner B M
J Clin Invest. 1980 May;65(5):982-8. doi: 10.1172/JCI109784.
To determine the physiological basis for the low glomerular filtration rate in chronic malnutrition, micropuncture studies were performed in Munich-Wistar rats chronically pair-fed isocaloric diets of either low (group 1, nine rats) or high protein content (group 2, nine rats). Despite the absence of hypoalbuminemia, average values for single nephron and total kidney glomerular filtration rate were nearly 35% lower in group 1 than in group 2. Mean values for glomerular capillary and Bowman's space hydraulic pressures were essentially identical in the two groups, thereby excluding glomerular transcapillary hydraulic pressure difference as the cause for the low filtration rates in group 1 animals. On the other hand, average glomerular capillary plasma flow rate and glomerular capillary ultrafiltration coefficient were significantly lower (by approximately 25 and approximately 50%, respectively) in group 1 than in group 2. The fall in glomerular capillary plasma flow rate was the consequence of increased afferent and efferent arteriolar resistances. Plasma and erythrocyte volumes were found to be equal in five additional pairs of group 1 and group 2 rats. Thus, the substantial alterations in the ultrafiltration coefficient, glomerular capillary plasma flow rate, and renal arteriolar resistances responsible for the low filtration rate in group 1 animals were not merely a consequence of decreased circulating blood or plasma volumes. Mean values for glomerular cross sectional area were significantly lower in group 1 than in group 2 despite similar values for kidney weight in the two groups. This reduction in glomerular cross sectional area in group 1 rats is presumed to reflect a decrease in effective filtration surface area and therefore likely accounts, at least in part, for the decline in ultrafiltration coefficient observed in this group.Finally, since the daily caloric intake of group 2 animals was restricted because of pair feeding requirements tied to the group 1 rats, we studied a third group of seven rats (group 3) allowed an ad lib. intake of the same high protein diet as given to group 2 rats. Average values for single nephron glomerular filtration rate and its determinants were found to be indistinguishable between groups 2 and 3. These results suggest that low protein intake, rather than calorie deficiency per se, is primarily responsible for the reduction in filtration rate seen in this experimental model of chronic malnutrition.
为了确定慢性营养不良时肾小球滤过率降低的生理基础，对慕尼黑-威斯塔大鼠进行了微穿刺研究，这些大鼠长期成对喂养等热量饮食，蛋白质含量低（第1组，9只大鼠）或高（第2组，9只大鼠）。尽管没有低白蛋白血症，但第1组的单个肾单位和总肾肾小球滤过率的平均值比第2组低近35%。两组的肾小球毛细血管和鲍曼间隙液压平均值基本相同，从而排除了肾小球跨毛细血管液压差是第1组动物滤过率低的原因。另一方面，第1组的平均肾小球毛细血管血浆流速和肾小球毛细血管超滤系数明显低于第2组（分别约低25%和约50%）。肾小球毛细血管血浆流速的下降是入球和出球小动脉阻力增加的结果。在另外五对第1组和第2组大鼠中，发现血浆和红细胞体积相等。因此，第1组动物滤过率低所涉及的超滤系数、肾小球毛细血管血浆流速和肾小动脉阻力的显著改变不仅仅是循环血液或血浆量减少的结果。尽管两组肾脏重量相似，但第1组的肾小球横截面积平均值明显低于第2组。第1组大鼠肾小球横截面积的减小被认为反映了有效滤过表面积的减少，因此可能至少部分解释了该组观察到的超滤系数的下降。最后，由于第2组动物的每日热量摄入因与第1组大鼠的成对喂养要求而受到限制，我们研究了第三组7只大鼠（第3组），允许它们自由摄入与第2组大鼠相同的高蛋白饮食。发现第2组和第3组之间单个肾单位肾小球滤过率及其决定因素的平均值没有差异。这些结果表明，低蛋白摄入而非热量缺乏本身是该慢性营养不良实验模型中滤过率降低的主要原因。
