Kojima T, Mitaka T, Shibata Y, Mochizuki Y
Department of Pathology, Sapporo Medical University School of Medicine, Japan.
J Cell Sci. 1995 Aug;108 ( Pt 8):2771-80. doi: 10.1242/jcs.108.8.2771.
In the adult rat hepatocyte, the gap junction proteins consist of a major component, connexin32 (Cx32) and a minor component, connexin26 (Cx26). Although we recently reported our success in inducing and maintaining Cx32 in adult rat hepatocytes cultured in serum-free L-15 medium supplemented with epidermal growth factor and 2% dimethyl sulfoxide, it was very difficult to induce Cx26 in the primary hepatocytes. In the present study, we found that the addition of 10(-7) M glucagon into the culture medium could dramatically induce Cx26 mRNA and protein. Although the expression of Cx32 mRNA was also influenced by glucagon, the increase of the expression was small. Immunocytochemically, Cx26-positive spots were observed between most adjacent cells and were co-localized with the Cx32-positive spots. We also examined whether 0.5 mM dibutyl cyclic AMP could induce expression of Cx26 in the cells. The effect of dexamethasone on the expression of Cx26 mRNA compared to that of Cx32 mRNA was examined. For the induction and maintenance of Cx26 mRNA, more than 10(-7) M dexamethasone was necessary in this culture. These results suggest that expression of Cx26 in hepatocytes may be regulated by the concentrations of glucagon and glucocorticoid hormones.
在成年大鼠肝细胞中，间隙连接蛋白由一种主要成分连接蛋白32（Cx32）和一种次要成分连接蛋白26（Cx26）组成。尽管我们最近报道了在添加表皮生长因子和2%二甲基亚砜的无血清L-15培养基中培养的成年大鼠肝细胞中成功诱导并维持Cx32的表达，但在原代肝细胞中诱导Cx26却非常困难。在本研究中，我们发现向培养基中添加10⁻⁷ M胰高血糖素可显著诱导Cx26 mRNA和蛋白的表达。尽管Cx32 mRNA的表达也受胰高血糖素影响，但表达增加幅度较小。免疫细胞化学分析显示，在大多数相邻细胞之间观察到Cx26阳性斑点，且与Cx32阳性斑点共定位。我们还检测了0.5 mM二丁酰环磷腺苷是否能诱导细胞中Cx26的表达。研究了地塞米松对Cx26 mRNA与Cx32 mRNA表达的影响。在这种培养中，为诱导并维持Cx26 mRNA的表达，地塞米松浓度需超过10⁻⁷ M。这些结果表明，肝细胞中Cx26的表达可能受胰高血糖素和糖皮质激素浓度的调节。
