Influence of extracellular matrix overlay and medium formulation on the induction of cytochrome P-4502B enzymes in primary cultures of rat hepatocytes

The effect of medium formulation, composition of extracellular matrix overl ay, and culture dish material on liver microsomal cytochrome P-450 (CYP) 2B induction by phenobarbital (PB) was investigated in primary cultures of ra t hepatocytes. When hepatocytes were maintained on Permanox dishes with an overlay of either collagen (type I) or Matrigel, Williams' E medium was sup erior to other medium formulations in terms of the magnitude of induction o f CYP2B on a per milligram microsomal protein basis. Modified Chee's medium (MCM) and hepatocyte culture medium were intermediate in their capacity to sustain induction of CYP2B by PB, and Dulbecco's modified Eagle's medium w as slightly less effective. The overall induction of CYP2B activity by PB w as, on average, 50% lower in hepatocytes cultured on polystyrene dishes (LU X), Little or no difference was observed between hepatocytes overlaid with collagen and those overlaid with Matrigel, MCM was superior to Williams' E medium in terms of the yield of microsomal protein and the ultrastructural features of the hepatocyte monolayers. CYP2B induction by PB was optimal af ter 3 days of treatment in either medium. CYP1A, CYP3A, and CYP4A activitie s could be induced in vitro by prototypical inducing agents in hepatocytes cultured on Permanox dishes with MCM and a Matrigel overlay to comparable l evels observed in vivo. The results of these studies show that medium formu lation and culture vessel material, but not the type of extracellular matri x overlay, have significant effects on the induction of CYP enzymes in cult ured rat hepatocytes maintained in a sandwich configuration.