Precocious induction of arginase in primary cultures of fetal rat hepatocytes.

Fetal rat hepatocytes were isolated and cultured in primary culture to investigate activity changes of arginase under defined conditions. In hormone-free medium, cultured cells maintained the enzyme activity at levels equal to that of freshly isolated cells for at least 4 d. Arginase activity could be induced by dexamethasone in hepatocytes isolated from 16.5-d-old fetuses although cells were competent to respond to glucagon only at the stage of 18.5 d. The combination of the two hormones induced greater levels of arginase activity than the individual compounds. These findings indicate that glucocorticoid and glucagon receptors appear early and sequentially before birth and reveal that cultured fetal hepatocytes provide a suitable system for the investigation of the role of hormones in the initiation of enzyme synthesis.