Holstege A, Leser H G, Pausch J, Gerok W
Eur J Biochem. 1985 May 15;149(1):169-73. doi: 10.1111/j.1432-1033.1985.tb08907.x.
Kupffer cells, endothelial cells, and hepatocytes were separated by centrifugal elutriation. The rate of uracil formation from [2-14C]uridine, the first step in uridine catabolism, was monitored in suspensions of the three different liver cell types. Kupffer cells demonstrated the highest rate of uridine phosphorolysis. 15 min after the addition of the nucleoside the label in uracil amounted to 51%, 13%, and 19% of total radioactivity in the medium of Kupffer cells, endothelial cells, and hepatocytes, respectively. If corrected for Kupffer cell contamination, hepatocyte suspensions demonstrated similar activities as endothelial cells. In contrast to non-parenchymal cells, hepatocytes continuously cleared uracil from the incubation medium. The lack of uracil consumption by Kupffer cells and endothelial cells points to uracil as the end-product of uridine catabolism in these cells. Kupffer cells and endothelial cells did not produce radioactive CO2 upon incubation in the presence of [2-14C]uridine. Hepatocytes, however, were able to degrade uridine into CO2, beta-alanine, and ammonia as demonstrated by active formation of volatile radioactivity from the labeled nucleoside. There was almost no detectable formation of thymine from thymidine or of cytosine, uracil, or uridine from cytidine by any of the different cell types tested. These results are in line with low thymidine phosphorolysis and cytidine deamination in rat liver. Our studies suggest a co-operation of Kupffer cells, endothelial cells, and hepatocytes in the breakdown of uridine from portal vein blood with uridine phosphorolysis predominantly occurring in Kupffer cells and with uracil catabolism restricted to parenchymal liver cells.
通过离心淘析法分离枯否细胞、内皮细胞和肝细胞。在三种不同肝细胞类型的悬浮液中监测尿苷分解代谢第一步即[2-¹⁴C]尿苷生成尿嘧啶的速率。枯否细胞表现出最高的尿苷磷酸解速率。加入核苷15分钟后，尿嘧啶中的标记物分别占枯否细胞、内皮细胞和肝细胞培养基中总放射性的51%、13%和19%。若校正枯否细胞污染，肝细胞悬浮液表现出与内皮细胞相似的活性。与非实质细胞不同，肝细胞持续从孵育培养基中清除尿嘧啶。枯否细胞和内皮细胞不消耗尿嘧啶表明尿嘧啶是这些细胞中尿苷分解代谢的终产物。在[2-¹⁴C]尿苷存在下孵育时，枯否细胞和内皮细胞不产生放射性二氧化碳。然而，肝细胞能够将尿苷降解为二氧化碳、β-丙氨酸和氨，这可通过标记核苷中挥发性放射性的活跃形成得到证明。在所测试的任何不同细胞类型中，几乎检测不到胸苷生成胸腺嘧啶或胞苷生成胞嘧啶、尿嘧啶或尿苷。这些结果与大鼠肝脏中低胸苷磷酸解和胞苷脱氨作用一致。我们的研究表明，枯否细胞、内皮细胞和肝细胞在分解门静脉血中的尿苷方面存在合作，尿苷磷酸解主要发生在枯否细胞中，而尿嘧啶分解代谢仅限于肝实质细胞。
