DNA synthesis in primary cultures of adult rat hepatocytes in a defined medium: Effects of epidermal growth factor, insulin, glucagon, and cyclic‐AMP

Abstract

Epidermal growth factor (EGF) especially in combination with insulin and glucagon, has been shown to stimulate DNA synthesis in liver cells, both in the whole animal and in cell cultures. As a further development we have found that in primary monolayer cultures of freshly isolated adult rat liver parenchymal cells, in which contamination with nonparenchymal cells was negligible, DNA synthesis was substantially stimulated by these substances. In control cultures, incorporation of [3H]thymidine into DNA and labeling of nuclei in autoradiographs was low. The stimulation by EGF was enhanced by insulin and glucagon, whereas these hormones by themselves exhibited only limited activity. These observations were made in cultures of hepatocytes that were never exposed to serum, even during cell isolation and plating. Hence for stimulation of DNA synthesis under these conditions neither serum factors nor interactions with other types of cells or their products were required. The effects of glucagon were reproduced by substances that elevate intracellular concentration of cyclic-AMP, including cholera toxin, isoproterenol, and methylisobutylxanthine. These various substances, especially EGF, glucagon, or cyclic-AMP, altered the morphological characteristics of the cultures during early stages, promoting cellular spreading and aggregation.

Cyclic AMP signalling pathway and cellular proliferation: induction of CREM during liver regeneration

“…cAMP has been strongly implicated in the regulation of proliferation during regenerating liver. Experiments in vitro with primary hepatocytes have demonstrated that transient cAMP induction increases DNA synthesis in the presence of Epidermal Growth Factor (EGF), while constant cAMP treatment inhibits DNA synthesis (McGowan et al, 1981;Diehl et al, 1992). Therefore, we speculate that the ®rst peak of cAMP, and thus the associated increase in ICER expression, is linked with the transient upregulation of genes that are expressed in G1 phase (e.g.…”

Cyclic AMP signalling and cellular proliferation: regulation of CREB and CREM

“…In vitro studies with primary hepatocytes have demonstrated that transient cAMP induction increases DNA synthesis in the presence of epidermal growth factor (EGF), while constant cAMP treatment inhibits DNA synthesis [4,17]. Therefore, we speculate that the first peak of cAMP, and thus the associated increase in ICER expression, is linked with the transient upregulation of genes that are expressed in Gl phase (e.g.…”

Growth induction of hepatic stimulator substance in he-patocytes through its regulation on EGF receptors

“…It was reported that HSS alone had little effect on the DNA synthesis of the resting hepatocytes as in the primary culture hepatocytes, but in contrast, if combined with EGF, it could amplify the growth response of the cells to EGF both in vitro [20,21] and in vivo [22]. The EGF participation in the regulation of liver proliferation was demonstrated in the down-regulation of EGF receptor following partial hepatectomy [23].…”