胆酸摄取与分离的大鼠肝细胞

Cholic acid uptake and isolated rat hepatocytes.

作者信息

Anwer M S, Kroker R, Hegner D

出版信息

Hoppe Seylers Z Physiol Chem. 1976 Nov;357(11):1477-86. doi: 10.1515/bchm2.1976.357.2.1477.

DOI:10.1515/bchm2.1976.357.2.1477

Abstract

Cholic acid uptake was studied in isolated rat hepatocytes using a centrifugal filtration technique to allow rapid sampling. Hepatocytes were found to adsorb as well as to transport cholic acid. The adsorption was characterized by a capacity of 24 nmol X mg cell protein-1 and an association constant of 0.59 X 103 M-1. Cholic acid uptake was linear with respect to concentration at or below 10 degree C, suggesting a unsaturable uptake process which was considered to represent simple diffusion and is quantitated by a diffusion coefficient of 1.76 pmol cholic acid X min-1 X mg protein-1 X muM-1. Above 10 degrees C the uptake curve was biphasic. After subtracting the unsaturable component from uptake rates at higher temperatures, a curve showing saturable kinetics resulted. The apparent Km and V values at 37 degrees C were calculated to be 31muM and 0.8 nmol X min-1 X mg protein-1 respectively. This saturable uptake process was temperature-dependent with an activation energy of 13 kcal X mol-1 (5.44 X 104 J X mol-1) and was inhibited by oligomycin and KCN. Countertransport was demonstrated with cholic, taurocholic and chenodeoxycholic acids. The results suggest that cholic acid is transported by an energy-dependent carrier-mediated process in addition to simple diffusion by hepatocytes, and that the postulated carrier has affinity for other bile acids.

摘要

采用离心过滤技术对分离的大鼠肝细胞中胆酸摄取进行了研究，以实现快速取样。发现肝细胞既能吸附又能转运胆酸。吸附的特征在于容量为24 nmol·mg细胞蛋白⁻¹，缔合常数为0.59×10³ M⁻¹。在10℃及以下，胆酸摄取与浓度呈线性关系，表明存在一个不饱和摄取过程，该过程被认为代表简单扩散，其扩散系数为1.76 pmol胆酸·min⁻¹·mg蛋白⁻¹·μM⁻¹。在10℃以上，摄取曲线呈双相。从较高温度下的摄取速率中减去不饱和成分后，得到一条显示饱和动力学的曲线。计算出37℃时的表观Km和V值分别为31μM和0.8 nmol·min⁻¹·mg蛋白⁻¹。这种饱和摄取过程具有温度依赖性，活化能为13 kcal·mol⁻¹（5.44×10⁴ J·mol⁻¹），并受到寡霉素和KCN的抑制。胆酸、牛磺胆酸和鹅去氧胆酸均表现出反向转运。结果表明，除了肝细胞的简单扩散外，胆酸还通过能量依赖的载体介导过程进行转运，并且假定的载体对其他胆汁酸具有亲和力。