title: Proliferative synergy of ANG II and EGF in porcine aortic vascular smooth muscle cells.
abstract: To test growth effects of angiotensin II (ANG II) in porcine vascular smooth muscle cells (VSMC) and potential ANG II synergy with epidermal growth factor (EGF), we exposed subconfluent, near-quiescent porcine aortic VSMC to ANG II, EGF, or ANG II + EGF (each 10(-9) M) in Dulbecco's modified Eagle's-Ham's F-12 medium with insulin + 0.4% fetal calf serum (FCS) selected for minimal ANG II-degrading capacity. Cell number and DNA and protein synthesis (by [3H]-thymidine and [35S]methionine incorporation, respectively) were determined serially over 1-6 days. ANG II alone induced an early 20% increase and then a plateau in cell number over the 0.4% FCS control (P < 0.01; n = 8), thus without sustained increase in proliferation rate. Yet ANG II alone did not increase fractional DNA or protein synthesis (each as cpm/10(3) cells) and, by flow cytometry, reduced S phase fraction without increase in cell size. EGF alone induced brisk DNA synthesis yet minimal cell division over days 0-4, thus late-cycle arrest. ANG II + EGF, despite no increase in fractional DNA or protein synthesis rates over EGF alone, induced significant indomethacin-resistant dose-dependent (P < 0.001) increase in cell proliferation rate over EGF alone with a median effective dose of 5 x 10(-10) M ANG II, thus proliferative synergy. We propose that 1) ANG II induces a subpopulation of cells arrested in or beyond S phase to proceed through mitosis but does not influence G1 traversal or S phase entry and 2) ANG II + EGF achieve proliferative synergy by complementary actions at sequential cell cycle loci, with EGF supporting progression from G0/G1 to S phase and ANG II inducing completion of mitosis by cells already in or beyond S phase ("late-cycle completion").
authors.affiliation: Department of Medicine, Portland Veterans Affairs Medical Center, Oregon 97201.
authors.forename: S P
authors.initials: SP
authors.lastname: Bagby
authors.forename: E A
authors.initials: EA
authors.lastname: Kirk
authors.forename: L H
authors.initials: LH
authors.lastname: Mitchell
authors.forename: M M
authors.initials: MM
authors.lastname: O'Reilly
authors.forename: W E
authors.initials: WE
authors.lastname: Holden
authors.forename: P E
authors.initials: PE
authors.lastname: Stenberg
authors.forename: A C
authors.initials: AC
authors.lastname: Bakke
mesh_terms: D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001013:Aorta, Thoracic / Q000166:cytology*; D002452:Cell Count / Q000187:drug effects; D002453:Cell Cycle; D002455:Cell Division / Q000187:drug effects; D002470:Cell Survival; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D007213:Indomethacin / Q000494:pharmacology; D009131:Muscle, Smooth, Vascular / Q000166:cytology*; D016196:S Phase; D013552:Swine; D013997:Time Factors
chemical_list: D000804:Angiotensin II; D004815:Epidermal Growth Factor; D007213:Indomethacin