Development of gap junctional channels and intercellular communication in rat liver during ontogenesis

Background/Aims: We investigated the expression of connexin (Cx) 32 and 26 subunit proteins of the gap junction (GJ) in the rat liver during ontogenes is to clarify their roles in control of growth and differentiation, and obs erved their channels in association with development or gap junctional inte rcellular communication (GJIC), Methods: The expression of Cx32 and 26 in prenatal and postnatal livers was examined by Western blot and immunofluorescence. GJ channels were investig ated not only by double immunofluorescence study but also by immunogold ele ctron microscopy. The spread of lucifer yellow 5 min after its microinjecti on was examined in the cultured liver tissues, Results: 1) Western blot showed the expression of both Cx from the late sta ge of gestation and their peak a week after birth. 2) Cx32- or 26-positive plaques were scattered on hepatocytes of the fetal liver and some of them w ere colocalized; both were increased just after birth. On day 7 after birth , Cx32-positive plaques were present on all hepatocytes within a lobule, an d Cx26-positive plaques were distributed in the periportal area. 3) Double- immunogold electron microscopy just after birth showed that most GJ channel s were homotypic type of Cx32 or 26, and that few were heterotypic, On day 7 after birth, most channels had the homotypic type of type of Cx32 in the middle and pericentral areas, and there was a heterotypic type of Cx32 and 26 in the periportal area. 4) The dye transfer of lucifer yellow showed a w ider spread in the liver tissues on day 7 after birth than on day 1. Conclusion: Increased GJ formation and compatibility or incompatibility of GJ channels are closely associated with development of GJIC, and GJIC may d evelop at cytodifferentiation during ontogenesis.