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The CCAAT/enhancer-binding protein α (C/EBPα) is essential for maintaining the differentiated state of hepatocytes in vivo. C/EBPα activates albumin transcription and coordinates the expression of multiple ornithine cycle enzymes involved in urea production. We have examined the effects of the C/EBPα knock-in gene on the mRNA and protein expression of genes involved in liver-specific functions, such as albumin and urea production. Albumin mRNA and protein levels are higher in knock-in hepatocytes compared with wild-type hepatocytes. mRNA levels for the ornithine cycle enzymes, namely arginase, carbamylphosphate synthetase 1, and ornithine transcarbamylase, also increase. Albumin secretion and urea production are sustained at higher levels in culture in knock-in hepatocytes. We have previously established that C/EBPα induces early liver glycogen storage in C/EBPα knock-in mice. Our present observations underline the importance of C/EBPα in liver metabolism and suggest that the induction of C/EBPα expression enhances hepatocyte function. [ABSTRACT FROM AUTHOR]