title: EGF is incomplete mitogen in porcine aortic smooth muscle cells: DNA synthesis without cell division.
abstract: To characterize growth effects of epidermal growth factor (EGF) in subconfluent quiescent porcine aortic vascular smooth muscle cells (VSMC), we measured DNA and protein synthesis by [3H]thymidine (Thd) and [35S]methionine (Met) incorporation, respectively, and cell proliferation rates over 0-6 days in Dulbecco's modified Eagle's-Ham's F-12 media containing 0.4% fetal calf serum (FCS) and insulin. EGF induced dose-dependent [3H]Thd uptake (P less than 0.001); after 10(-9) M EGF, DNA synthesis rate peaked at 24 h, averaging 77% of the response to 10% FCS, and then declined steeply with nadir at 48-60 h. Unexpectedly, EGF failed to induce cell proliferation in the first 4 days, leaving this initial burst of DNA synthesis (12-60 h) uncoupled from cell division. A second lesser but sustained phase of increased DNA synthesis, apparent by day 3-4, was associated with a small increase in cell number on day 6 (P less than 0.05). The early unsustained burst of DNA synthesis reflects EGF's potent mitogenic efficacy for DNA synthesis (G1- to S-phase traversal), probably acting on a subset of cells partially synchronized initially at an EGF-responsive G0/G1 locus; the minimal cell division despite brisk DNA synthesis documents EGF's limited efficacy for (or inhibition of) late cell-cycle events required for completion of mitosis. Late cell-cycle processes are thus rate limiting. EGF also increased protein synthetic rate over control (P less than 0.03) but to a lesser degree (P less than 0.01) than 10% FCS. Indomethacin (10(-6) M) did not alter DNA or proliferative responses to 10(-9) M EGF but transiently augmented EGF-induced protein synthesis (P less than 0.025) at 24 h only.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Medicine, Portland Veterans Administration Medical Center, Oregon 97201.
authors.forename: S P
authors.initials: SP
authors.lastname: Bagby
authors.forename: M M
authors.initials: MM
authors.lastname: O'Reilly
authors.forename: E A
authors.initials: EA
authors.lastname: Kirk
authors.forename: L H
authors.initials: LH
authors.lastname: Mitchell
authors.forename: P E
authors.initials: PE
authors.lastname: Stenberg
authors.forename: M T
authors.initials: MT
authors.lastname: Makler
authors.forename: A C
authors.initials: AC
authors.lastname: Bakke
mesh_terms: D000818:Animals; D001011:Aorta; D002455:Cell Division / Q000502:physiology*; D002478:Cells, Cultured; D004247:DNA / Q000096:biosynthesis*; D004815:Epidermal Growth Factor / Q000502:physiology*; D007213:Indomethacin / Q000494:pharmacology; D007700:Kinetics; D008715:Methionine / Q000378:metabolism; D008854:Microscopy, Electron; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000648:ultrastructure; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D014176:Protein Biosynthesis; D011865:Radioisotope Dilution Technique; D013462:Sulfur Radioisotopes; D013552:Swine; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
chemical_list: D013462:Sulfur Radioisotopes; D014316:Tritium; D004815:Epidermal Growth Factor; D004247:DNA; D008715:Methionine; D011451:Prostaglandin-Endoperoxide Synthases; D013936:Thymidine; D007213:Indomethacin