Diverse expression of ErbB receptor proteins during rat liver development and regeneration

Background & Aims: The protein expression and interactions of the ErbB receptors were examined in different liver proliferation models in vivo and in vitro, including ontogeny and regeneration following partial hepatectomy. Methods: Expression and tyrosine phosphorylation status of specific ErbB proteins were studied by immunologic methods. Results: The epidermal growth factor receptor, ErbB2, and ErbB3 were the only ErbB proteins detected in the liver parenchyma on embryonic day 19. Erb82 disappeared by the third week after birth and could not be appreciably induced in the adult animal by partial hepatectomy. ErbB2 was also detected in multi-potent stem (RLE) and hepatoma (H4IIe) cell lines as well as in fetal, but not adult, hepatocyte cultures. Only epidermal growth factor receptor and Erb83 were detected in adult liver, and both showed circadian variation in protein expression. Erb84 was not detected in any model. Patterns of ligand-induced ErbB phosphorylation differed between fetal and adult hepatocytes. Conclusions: Complex and independent programs regulate the ErbB receptors, with implications for differential cell signaling in hepatic development and regeneration.