Chojkier M
J Clin Invest. 1986 Aug;78(2):333-9. doi: 10.1172/JCI112581.
Although hepatocytes produce collagen in vitro, their contribution to hepatic collagen synthesis in vivo is unknown. To answer this question, we injected rats intraperitoneally with [3H]proline and [14C]ornithine. [3H]Proline labeled prolyl-t-RNA in both hepatocytes and nonparenchymal cells. In contrast, [14C]ornithine was rapidly converted to [14C]arginine via the urea cycle only in hepatocytes, labeling arginyl-t-RNA. Approximately 60% of the 14C in albumin and transferrin was present as arginine while the remainder was found in proline and related amino acids. As expected for proteins that have the same proline/arginine ratio and that are produced solely by the hepatocyte, the [3H]proline/[14C]arginine ratio was very similar in albumin and transferrin. Conversely, in nonparenchymal cells a negligible percentage of 14C was present as arginine. A sizeable percentage of the 14C in hepatic collagen was present as arginine; given the greater proline(+hydroxyproline)/arginine ratio in hepatic collagen, our data indicate that in normal rats, hepatocytes contribute most of newly synthesized hepatic collagen.
虽然肝细胞在体外能产生胶原蛋白，但其在体内对肝脏胶原蛋白合成的贡献尚不清楚。为了回答这个问题，我们给大鼠腹腔注射了[3H]脯氨酸和[14C]鸟氨酸。[3H]脯氨酸标记了肝细胞和非实质细胞中的脯氨酰 - t - RNA。相比之下，[14C]鸟氨酸仅在肝细胞中通过尿素循环迅速转化为[14C]精氨酸，标记精氨酰 - t - RNA。白蛋白和转铁蛋白中约60%的14C以精氨酸形式存在，其余则存在于脯氨酸及相关氨基酸中。对于具有相同脯氨酸/精氨酸比例且仅由肝细胞产生的蛋白质而言，白蛋白和转铁蛋白中的[3H]脯氨酸/[14C]精氨酸比例非常相似。相反，在非实质细胞中，14C以精氨酸形式存在的比例可忽略不计。肝脏胶原蛋白中相当大比例的14C以精氨酸形式存在；鉴于肝脏胶原蛋白中脯氨酸（+羟脯氨酸）/精氨酸比例更高，我们的数据表明，在正常大鼠中，肝细胞贡献了大部分新合成的肝脏胶原蛋白。
