title: Retinyl acetate inhibits platelet-derived growth factor-induced Ca2+ signals in C3H 10T1/2 fibroblasts.
abstract: Mitogenic stimulation of density-arrested C3H 10T1/2 mouse fibroblasts by serum or purified platelet-derived growth factor (PDGF) was potently inhibited by retinyl acetate (RAc; IC50 = 0.1 microgram/ml, 0.3 x 10(-6) M) when administered during the first 2 hours of mitogen exposure. This inhibitory effect of RAc coincided with a period early in the cell growth-division cycle when density-arrested C3H 10T1/2 cells stimulated by PDGF were found to require physiological levels of extracellular Ca2+ for the transition from G0 to G1 of the cell cycle. To determine if the inhibitory effect of RAc was mediated through alterations in the Ca2+ signaling pathway induced by mitogens, we examined Fura-2-loaded fibroblasts for changes in the Ca2+ response elicited by PDGF. Addition of PDGF (5 ng/ml) induced a transient increase in the [Ca2+]i that was not significantly effected by the extracellular Ca2+ concentration. Treatment of cells with RAc caused a concentration- and time-dependent inhibition of this PDGF-stimulated Ca2+ flux (IC50 = 0.45 microgram/ml or 1.5 x 10(-6) M; t1/2 = 15 min), whereas release of intracellularly stored Ca2+ by thrombin was unaffected by RAc (1.2 micrograms/ml, 4 x 10(-6) M). Treatment with RAc did not significantly affect PDGF binding to cell surface receptors or the generation of inositol phosphates. These results suggest that the mechanism by which RAc inhibits PDGF- or serum-induced mitogenesis is through modulation of the Ca2+ signal stimulated by PDGF, and thereby depriving the cell of a rise in intracellular Ca2+ necessary for progression through the cell cycle.
authors.affiliation: Basic Science Program, University of Hawaii, Manoa, Honolulu 96813.
authors.forename: T D
authors.initials: TD
authors.lastname: Hill
authors.forename: A L
authors.initials: AL
authors.lastname: Boynton
authors.forename: N M
authors.initials: NM
authors.lastname: Dean
authors.forename: L J
authors.initials: LJ
authors.lastname: Mordan
mesh_terms: D000818:Animals; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D003470:Culture Media; D004261:DNA Replication / Q000187:drug effects; D004224:Diterpenes; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D007294:Inositol / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D010716:Phosphatidylinositols / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D000084562:Retinyl Esters; D015398:Signal Transduction / Q000187:drug effects*; D013917:Thrombin / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D014801:Vitamin A / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D003470:Culture Media; D004224:Diterpenes; D010716:Phosphatidylinositols; D010982:Platelet-Derived Growth Factor; D000084562:Retinyl Esters; D014801:Vitamin A; C009166:retinol acetate; D007294:Inositol; D013917:Thrombin; D002118:Calcium; D013936:Thymidine