Armato U, Ribecco M, Guerriero C, Testolin L, Whitfield J F
Department of Histology, Medical School, University of Verona, Italy.
J Cell Physiol. 1994 Oct;161(1):55-62. doi: 10.1002/jcp.1041610108.
The cells in nearly pure (96-98%) primary cultures of hepatocytes from neonatal rat liver in high (1.0 mM)-Ca2+, serum-free, synthetic HiWo5Ba2000 medium initiated DNA synthesis and entered mitosis between 11 and 30 h after the addition of 10 ng/ml EGF. During the 10-h prereplicative period, the cultured hepatocytes, like regenerating rat liver cells, generated two large cyclic AMP transients, one peaking between 30 min and 2 h and the other around 6 h. Hepatocytes stimulated by the same concentration of EGF in low (0.02 mM)-Ca2+ medium increased cyclic AMP synthesis as much as the EGF-treated hepatocytes in high-Ca2+ medium, but they released the additional cyclic AMP into the medium and could not generate prereplicative internal cyclic AMP surges, initiate DNA replication, or enter mitosis. These results suggest that one of the ways external Ca2+ controls prereplicative development of hepatocytes is to restrain the release of cyclic AMP and thus enable the cell to accumulate enough internal cyclic AMP to stimulate events required to initiate DNA replication.
在高钙（1.0 mM）、无血清的合成HiWo5Ba2000培养基中，来自新生大鼠肝脏的近纯（96 - 98%）原代肝细胞培养物中的细胞，在添加10 ng/ml表皮生长因子（EGF）后11至30小时开始DNA合成并进入有丝分裂。在10小时的复制前期，培养的肝细胞与再生的大鼠肝细胞一样，产生两个大的环磷酸腺苷（cAMP）瞬变，一个在30分钟至2小时达到峰值，另一个在6小时左右达到峰值。在低钙（0.02 mM）培养基中，相同浓度的EGF刺激的肝细胞，其cAMP合成增加量与高钙培养基中EGF处理的肝细胞相同，但它们将额外的cAMP释放到培养基中，无法产生复制前的细胞内cAMP激增，无法启动DNA复制或进入有丝分裂。这些结果表明，细胞外钙控制肝细胞复制前发育的一种方式是抑制cAMP的释放，从而使细胞能够积累足够的细胞内cAMP，以刺激启动DNA复制所需的事件。
