Keiding S, Henriksen O, Sejrsen P
Department of Clinical Physiology, Bispebjerg Hospital, Copenhagen, Denmark.
Acta Physiol Scand. 1988 Jul;133(3):335-42. doi: 10.1111/j.1748-1716.1988.tb08415.x.
Capillary permeability of [14C]inulin and [51Cr]EDTA was examined in human forearm in five healthy, subjects by indicator diffusion technique. Injections of, initially [125I]albumin and [14C]inulin, and after 30 min resting, of [125I]albumin and [51Cr]EDTA, were given in a brachial artery. During light exercise of the forearm, blood was sampled in 2-s periods from a deep cubital vein primarily draining muscles. The plasma flow rate, calculated as the dose of [125I]albumin in the injectate divided by the area under the curve for the venous concentration of 125I, was, on average, 8.5 ml min-1 100 g-1 forearm. Assuming [125I]albumin is a partially permeable tracer, a correction for extraction of albumin was performed. This gave extraction fractions of 0.107 +/- 0.015 (mean +/- SEM) for [14C]inulin and 0.377 +/- 0.033 for [51Cr]EDTA, respectively. The capillary permeability surface area product per 100 g tissue (CDC) was for [14C]inulin 0.90 +/- 0.19, and for [51Cr]EDTA 3.31 +/- 0.38 ml min-1 100 g-1 forearm. The average of the ratios of the CDC values of [51Cr]EDTA to those of [14C]inulin, 4.0 +/- 0.5, is significantly higher than the corresponding ratio between the measured free diffusion coefficients in water at 37 degrees C, 3.07 +/- 0.002 (N = 36 and 17, respectively). This indicates that there is some degree of restriction for [14C]inulin (MW 5200) relative to [51Cr]EDTA (MW 340.2) and it points to an 'equivalent pore radius estimate' of about 160 A in human muscle capillaries.
通过指示剂扩散技术，在5名健康受试者的人前臂中检测了[14C]菊粉和[51Cr]依地酸二钠的毛细血管通透性。最初将[125I]白蛋白和[14C]菊粉注入肱动脉，休息30分钟后，再将[125I]白蛋白和[51Cr]依地酸二钠注入。在前臂轻度运动期间，主要从引流肌肉的肘正中深静脉以2秒的间隔采集血液样本。以注射液中[125I]白蛋白的剂量除以静脉中125I浓度曲线下的面积计算的血浆流速，前臂平均为8.5 ml·min-1·100 g-1。假设[125I]白蛋白是一种部分可渗透的示踪剂，则对白蛋白的提取进行了校正。这使得[14C]菊粉的提取分数为0.107±0.015（平均值±标准误），[51Cr]依地酸二钠的提取分数为0.377±0.033。每100 g组织的毛细血管通透性表面积乘积（CDC），[14C]菊粉为0.90±0.19，[51Cr]依地酸二钠为3.31±0.38 ml·min-1·100 g-1前臂。[51Cr]依地酸二钠与[14C]菊粉的CDC值之比的平均值为4.0±0.5，显著高于37℃水中测量的自由扩散系数的相应比值3.07±0.002（分别为N = 36和17）。这表明相对于[51Cr]依地酸二钠（分子量340.2），[14C]菊粉（分子量5200）存在一定程度的限制，并且表明人肌肉毛细血管的“等效孔径估计”约为160 Å。
