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KMID : 0900919950190020095
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Korean journal of Animal Reproduction
1995 Volume.19 No. 2 p.95 ~ p.104
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Role of cAMP, EGF, IGF-I and Protein Phosphorylation in Mammary Development II. Interaction Effects of EGF, IGF-I and Photoreactive Cyclic AMP on DNA Synthesis and Protein Phosphorylation
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Abstract
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Mouse mammary epithelial cells(NMuMG) were maintained onto 6-well plates (3times105 cells/well) or chambered slide (1times104 cells/well), in DMEM supplemented with 10% fetal calf serum. After serum starvation for 24 hours, DMNB (1muM) was added and exposed to UV light (300nm, 3 second pulse) after 2 hours from DMNB addition in order to activate DMNB which induces a rapid transient increase in intracellular cAMP upon UV irradiation. EGF (100ng/ml) and/or IGF-I (10ng/ml) were treated at the time of UV irradiation. Nuclear labeling index was estimated as percent of nuclear labeled cells(percent of S phase of cells) by incorporation of 3H-thymidine into DNA(1 hour pulse with 1muCi/ml). DMNB(1muM), EGF (100ng/ml) and/or IGF-I (10ng/ml) signifciantly increased nuclear labeling index than those of control (P<0.05). Addition of DMNB＋EGF or DMNB＋EGF＋IGF-I showed the interaction effect in nuclear labeling index (P<0.05). Protein kinase A activities by addition of EGF, IGF-I or EGF＋IGF-I were 10.5, 9.8 or 9.4 unit/mg protein, respectively, and no statistical difference was found in comparison with control (P>0.05). Additon of DMNB＋EGF showed the moderate interaction effect on tyrosyl kinase activity (P<0.1). In the fluorography analysis, there were no specific protein phosphorylation patterns were found at 1 or 15 minute by addition of DMNB. EGF and/or IGF-I. These results suggest that the interaction effect in nuclear labeling index by addition DMNB and EGF could be mediated through the modulation of tyrosyl kinase activity by cAMP.
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KEYWORD
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