Miyazaki M, Wahid S, Bai L, Namba M
Department of Cell Biology, Okayama University Medical School, Japan.
Exp Cell Res. 1992 Jun;200(2):404-9. doi: 10.1016/0014-4827(92)90188-e.
Possible roles of dibutyryladenosine 3',5'-cyclic monophosphate (cAMP) and dibutyryl-guanosine 3',5'-cyclic monophosphate (cGMP) in regulation of hepatocyte DNA synthesis were examined using primary cultures of young-adult rat hepatocytes maintained in arginine-free medium. Throughout the experimental period, nonparenchymal cells were hardly observed in the selective medium. When epidermal growth factor (EGF) was added to the cultures, a transient increase in the intracellular cAMP level preceded the elevation of hepatocyte DNA synthesis. EGF-stimulated hepatocyte DNA synthesis was remarkably enhanced by the elevation of the intracellular cAMP level induced by treatment with cAMP alone or a combination of cAMP and theophylline, an inhibitor of cyclic nucleotide phosphodiesterase. Furthermore, the early elevation of intracellular cAMP alone, which was induced by treatment with the combination of cAMP and theophylline, caused a remarkable increase in hepatocyte DNA synthesis. On the other hand, addition of EGF to the cultures caused a rapid decrease in the intracellular cGMP level followed by an increase in hepatocyte DNA synthesis. EGF-stimulated hepatocyte DNA synthesis was severely suppressed or completely inhibited by the elevation of the intracellular cGMP level induced by treatment with cGMP alone or a combination of cGMP and dipyridamole, a specific inhibitor of cGMP phosphodiesterase. These findings indicate that cAMP and cGMP act oppositely on the regulation of DNA synthesis of young-adult rat hepatocytes in primary culture: cAMP plays a positive role, whereas cGMP plays a negative role. Also it is strongly suggested that an early elevation of the intracellular cAMP level is essential for the onset of DNA synthesis in hepatocyte primary cultures.
使用在无精氨酸培养基中培养的成年大鼠原代肝细胞，研究了二丁酰腺苷3',5'-环磷酸（cAMP）和二丁酰鸟苷3',5'-环磷酸（cGMP）在调节肝细胞DNA合成中的可能作用。在整个实验期间，在选择性培养基中几乎未观察到非实质细胞。当向培养物中添加表皮生长因子（EGF）时，肝细胞DNA合成升高之前，细胞内cAMP水平会短暂升高。单独使用cAMP或cAMP与环核苷酸磷酸二酯酶抑制剂茶碱联合处理诱导的细胞内cAMP水平升高，显著增强了EGF刺激的肝细胞DNA合成。此外，由cAMP和茶碱联合处理诱导的单独细胞内cAMP早期升高，导致肝细胞DNA合成显著增加。另一方面，向培养物中添加EGF会导致细胞内cGMP水平迅速下降，随后肝细胞DNA合成增加。单独使用cGMP或cGMP与cGMP磷酸二酯酶特异性抑制剂双嘧达莫联合处理诱导的细胞内cGMP水平升高，严重抑制或完全抑制了EGF刺激的肝细胞DNA合成。这些发现表明，cAMP和cGMP在原代培养的成年大鼠肝细胞DNA合成调节中起相反作用：cAMP起积极作用，而cGMP起消极作用。还强烈表明，细胞内cAMP水平的早期升高对于肝细胞原代培养中DNA合成的开始至关重要。
