Krag E, Phillips S F
J Clin Invest. 1974 Jun;53(6):1686-94. doi: 10.1172/JCI107720.
Absorption of the major human bile acids was studied in 12 healthy volunteers by steady state perfusion of the ileum in 112 experiments and of the jejunum in 48 experiments. Use of a randomized order of four perfusions on 1 day of study and use of up to 4 consecutive days of study in a subject allowed important comparisons of data from the same individuals. That there is active ileal absorption of chenodeoxycholic, glycochenodeoxycholic, and taurocholic acids in man was supported by the finding of saturation kinetics and of competition for absorption among conjugated bile acids. Values for apparent kinetic constants (apparent maximal transport velocity [()V(max)] and apparent Michaelis constant) in man are similar to those in other species. The ileum absorbed chenodeoxycholic acid more rapidly than its glycine conjugate, due mainly to a ninefold greater permeability for the free acid. Taurocholate had the highest ()V(max) and was absorbed more rapidly than glycochenodeoxycholate. Passive permeability of the jejunum to bile acids was twice that of the ileum, and the permeabilities to free and glycine-conjugated chenodeoxycholate were in the same ratio as in the ileum (9: 1). Jejunal permeability to chenodeoxycholic acid was three times that to cholic acid. Variation of intraluminal pH by up to 1.4 units did not influence jejunal uptake of free bile acids. These results, which are comparable with those from animal experiments, provide a basis for estimation of intestinal reabsorption of bile acids in intact man.
通过对12名健康志愿者进行112次回肠稳态灌注实验和48次空肠稳态灌注实验，研究了主要人体胆汁酸的吸收情况。在一天的研究中采用四种灌注的随机顺序，且在一名受试者中最多连续进行4天的研究，这使得能够对来自同一受试者的数据进行重要比较。胆酸、甘氨胆酸和牛磺胆酸在人体回肠存在主动吸收，这一观点得到了饱和动力学以及共轭胆汁酸吸收竞争现象的支持。人体中表观动力学常数（表观最大转运速度[()V(max)]和表观米氏常数）的值与其他物种相似。回肠对胆酸的吸收速度比对其甘氨酸共轭物更快，这主要是因为游离酸的通透性比其大九倍。牛磺胆酸盐的()V(max)最高，其吸收速度比甘氨胆酸盐更快。空肠对胆汁酸的被动通透性是回肠的两倍，对游离胆酸和甘氨酸共轭胆酸的通透性比例与回肠相同（9:1）。空肠对胆酸的通透性是对胆酸的三倍。管腔内pH值变化高达1.4个单位不会影响空肠对游离胆汁酸的摄取。这些结果与动物实验结果相当，为评估完整人体中胆汁酸的肠道重吸收提供了依据。
