Epidermal growth factor regulation of female-dependent CYP2A1 and CYP2C12 in primary rat hepatocyte culture.

In the present study, we describe the effects of medium composition in primary cultures of rat hepatocytes on the expression of two major constituent female-dependent CYP isoforms, CYP2C12 and CYP2A1. When female rat hepatocytes were cultured with the serum-free medium HepatoZYME, currently used to attain long-term maintenance of hepatocyte phenotypic expression, CYP2C12 mRNA and protein levels were markedly suppressed, despite the constant presence of growth hormone, the essential regulator of liver CYP2C12. Conversely, rat hepatocytes cultured in the serum-free medium Dulbecco's modified Eagle's medium-F12K, also supplemented with growth hormone, sustained near normal expression levels of CYP2C12 mRNA and protein for the 7 days of observations. Although media composition had no significant effect on mRNA expression of CYP2A1, protein content decreased dramatically in hepatocytes cultured with HepatoZYME medium. We were able to demonstrate the plasticity of the cells by restoring/suppressing the expression of CYP2C12 and CYP2A1 mRNA by reverting the culture conditions. Addition of the mitogen epidermal growth factor present in the HepatoZYME formulation to the Dulbecco's modified Eagle's medium-F12K culture media appreciably decreased expression of both CYP2C12 and CYP2A1 in female hepatocytes, while briefly sustaining levels of the cyclin inhibitor p21. Lastly, reduced CYP protein content observed in hepatocytes cultured with epidermal growth factor was not the result of an absence or reduction in the CCAAT/enhancer-binding protein alpha, a requisite transcription factor for CYP2C12 expression.