Effects of cAMP on ERK mitogen-activated protein kinase activity in hepatocytes do not parallel the bidirectional regulation of DNA synthesis. |
| |
Authors: | G H Thoresen E J Johasen T Christoffersen |
| |
Institution: | Department of Pharmacology, Faculty of Medicine, University of Oslo, Oslo, N-0316, Norway. |
| |
Abstract: | Previous studies have indicated that cAMP has bidirectional effects on epidermal growth factor (EGF)-induced DNA synthesis in cultured hepatocytes, acting to stimulate soon after plating (early G(1)) and to inhibit at later stages (nearer the G(1)/S transition). In this study we examined the role of the extracellular signal-regulated kinase (ERK) subgroup (p42/p44) of the mitogen activated protein (MAP) kinases both at growth-stimulatory and growth-inhibitory conditions. When added at low concentrations early during culturing, glucagon and 8-chlorophenylthio-cAMP (8-CPT-cAMP) did not increase MAP kinase activity, but enhanced the subsequent DNA synthesis. However, when administered at 24 h, glucagon and 8-CPT-cAMP decreased basal and EGF-induced MAP kinase activity and also inhibited EGF-induced DNA synthesis. Thus, although MAP kinase might play a role in the growth-inhibitory effect, it does not seem to be involved in growth-promoting regulation by cAMP in hepatocytes. |
| |
Keywords: | cAMP hepatocyte ERK MAP kinase DNA synthesis EGF |
本文献已被 ScienceDirect 等数据库收录! |
|