Modulation of intracellular signaling pathways by the extracellular matrix in primary rat hepatocytes

Investigations of liver-selective intracellular signaling cascades, m vitiv. are limited l>y the phenotypic stability of both established hepatoma lines and pri iTiary hopalocytes in culture. In this study, we examined the influence ot the extracellular matrix (ECM) environment on mitogen activated (MAPK), p70Sf| kinase and stress activated protein kinase (SAPK/JNK) cascades mediated liy anisomycin. epidermal growth factor (EGF), insulin, phorbol esters (PMA) and phénobarbital (PB). Primary rat hepatocyte.s were cultured for 72-96h either in the presence or absence of an overlay of KÖM (Matrigel) arid then exposed (o increasing concentrations of the respective agents. Prototypic. stimulation of MAPK wa.i observed independent of ECM with only EGF and PMA. The negative analog of PMA (a-PMA) and PII were without effect on all pathways examined. SAPK/JNK activation was observed exclusively with anisomycin and irrespective of KC'M. whereas the stimulation of p70Sfi kinase by anisomycin. insulin and EGF was significantly reduced in the absence of ECM. These re Mills demonstrate the importance of the ECM environment in the assessment of signaling events in primary hepatocytes and the subsequent extrapolation of drug action m riro. Supported by TSPHS Grant GM32281 (CMC).