In co-culture with non-parenchymal liver epithelial cells, rat hepatocytes show a marked increase in albumin and total protein synthesis when compared with cells maintained as pure populations in which an early decline in albumin secretion takes place. Analysis of the relative amounts of different mRNA sequences, determined by hybridization, indicated that the increase in protein synthesis resulted essentially from an increased level of the corresponding mRNAs. In addition, when cell-cell contacts were established between the two cell types several days after the seeding of hepatocytes, the stimulation of albumin secretion was similarly observed with a significant increase of the corresponding mRNA on days 10-14 of culture. Transcriptional assays, in which isolated nuclei were used for the study of RNA synthesis, showed that liverspecific gene transcription was significantly increased and maintained for at least 2 weeks. These results demonstrate for the first time long-term stabilization and reversibility of various specific mRNAs at high levels by adult hepatocytes in primary culture. They suggest that establishment of cellcell contacts between hepatocytes and liver epithelial cells are essential for the maintenance of a high rate of transcription of the liver-specific genes.
. We have identified the liver-regulating protein (LRP), a cell surface protein involved in the maintenance of hepatocyte differentiation when cocultured with rat liver epithelial cells (RLEC) . LRP was defined by immunoreactivity to a monoclonal antibody (mAb L8) prepared from RLEC. mAb L8 specifically detected two polypeptides of 85 and 73 kD in immunoprecipitation of both hepatocyte-and RLECiodinated plasma membranes . The involvement of these polypeptides, which are integral membrane proteins, in cell interaction-mediated regulation of hepatocytes was assessed by evaluating the perturbing effects of the antibody on cocultures with RLEC. Several parameters characteristic of differentiated hepatocytes were studied, such as liver-specific and house-keeping
Normal human adult hepatocytes were examined for their ability to synthesize and secrete factor V using primary culture. The culture medium contained both factor V and factor Va as determined by bioassay and activation experiments. Immunoprecipitation of newly synthesized labelled factor V showed the presence of both native factor V (m.w. 330,000) and two fragments of respective molecular weight 300,000 and 265,000. Northern blot analysis revealed the presence of a single 7 kb factor V mRNA in cultured human hepatocytes as in liver biopsies, together with fibrinogen beta and albumin transcripts. Relative levels of factor V, fibrinogen beta and albumin mRNAs differed when the cells cultured, suggesting that expression of the three corresponding genes might in part be independently regulated. Furthermore, addition of glucocorticoids enhanced factor V and fibrinogen beta mRNA levels 1.6- and 5-fold respectively, but did not significantly increase that of albumin. These results provide evidence that human hepatocytes actively participate in the synthesis of plasma factor V and constitute a valuable model to study the common and specific regulations involved in the control of the expression of this gene in human liver.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.