The Production of Urea from Ornithine in Rat Hepatoma Cells Continuously Cultured in a Chemically Defined Medium

R-Y121B cells derived from a rat Reuber hepatoma cell line have been grown serially in arginine-and glutamine-deprived, ornithine-supplemented Eagle's minimum essential medium. This cell line has the biochemical machinery to synthesize urea. It produces urea from ornithine via the urea cycle pathway. The synthesis of urea depends on the concentration of ornithine and acetylglutamate. There was no definite amino acid found to be the urea nitrogen source in R-Y121B cells.