Ammonia Removal Using Hepatoma Cells in Mammalian Cell Cultures

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• 作者：Yeon Sook Choi ; Doo-Young Lee ; Ick Young Kim ; Seongman Kang ; Kwangseog Ahn ; Hong Jin Kim ; Yeon Ho Jeong ; Gie-Taek Chun ; Jung Keug Park ; and Ik-Hwan Kim
• 刊名：Biotechnology Progress
• 出版年：2000
• 出版时间：October 2000
• 年：2000
• 卷：16
• 期：5
• 页码：760 - 768
• 全文大小：131K
• 年卷期：v.16,no.5(October 2000)
• ISSN：1520-6033

文摘

It was examined whether hepatocyte cell lines can be used for ammonia removal inmammalian cell cultures. It was found that there exists a critical ammoniumconcentration level for each hepatocyte cell to remove ammonia. Among the cells testedin this work, primary hepatocytes showed the strongest ammonia removal capabilityif ammonium concentration is higher than the critical level. However, primaryhepatocytes lost the liver function gradually and finally died after 2-3 weeks. Becauseof this limitation, primary hepatocytes were not appropriate to be used for ammoniaremoval in long-term cultures. Hep G2 cells, which are immortal, also showed a strongammonia removal activity. The ammonia removal activity of Hep G2 cells dependedon the concentration of ammonium in the medium, as in the case of primaryhepatocytes. However, urea could not be detected in the course of ammonia removalby Hep G2 cells. Instead of urea, Hep G2 cells secreted glutamine into the culturemedium. The capacity for ammonia removal was higher in the absence than in thepresence of glutamine. Thus we checked the activity of glutamine synthetase in theHep G2 cells. The level of glutamine synthetase activity increased with the additionof ammonium chloride. This result accounts for the ammonium concentrationdependency of Hep G2 cells in ammonia removal and glutamine synthesis. FurthermoreHep G2 cells could grow well in the absence of glutamine, which was necessarilyrequired in mammalian cell cultures. These results prove that glutamine formationserves as the primary mechanism of detoxifying ammonia in hepatocyte cell lines asexpected. In addition, it was demonstrated that ammonium level could be reduced38% and that erythropoietin production increased 2-fold in the mixed culture of HepG2 and recombinant CHO cells.