title: The protozoan Tetrahymena as a bioindicator to screen bioactive substances.
abstract: Tetrahymena thermophila has been used as a "swimming receptor" to study its chemotaxis in the presence of various bioactive substances from herbal plants. Chemotaxis of this ciliated protozoan is, in part, controlled by a cyclic GMP-dependent protein kinase (PKG), which can adjust ciliary beating. In this paper, the effects of Ginkgo biloba extract (GBE) and its main functional constituents, terpene lactones, flavonol glycosides and aglycones, on the chemotaxis and PKG activity of ciliates, were systematically investigated. GBE and its constituents exerted significant inhibition of chemotaxis and PKG activity in cells of T. thermophila. The minimal concentrations to completely inhibit chemotaxis of T. thermophila were 12, 25, 50, 100, 300, 400, 400, 500 microM, 2 mg/ml for isorhamnetin, kaempferol, quercetin, myricetin, isoquercitrin, quercetin-3-beta-d-galactoside, rutin, quercitrin, and GBE, respectively. The IC(50) values for PKG were 14, 17, 20, 25, 186, 78 microM, 0.157 mg/ml for isorhamnetin, kaempferol, quercetin, myricetin, isoquercitrin, rutin and GBE, respectively. The results indicate that the chemotaxis inhibition by GBE and its constituents and their effects on PKG are similar. This suggests that T. thermophila may be a potential experimental organism for screening other bioactive substances.
authors.affiliation: Food Science and Technology College, Huazhong Agricultural University, Wuhan 430070, Hubei Province, P.R. China. chen@imbg.ku.dk
authors.forename: Fusheng
authors.initials: F
authors.lastname: Chen
authors.forename: Vagn
authors.initials: V
authors.lastname: Leick
mesh_terms: D000818:Animals; D002633:Chemotaxis / Q000502:physiology*; D017869:Cyclic GMP-Dependent Protein Kinases / Q000502:physiology; D004791:Enzyme Inhibitors / Q000378:metabolism; D005419:Flavonoids / Q000378:metabolism; D020441:Ginkgo biloba / Q000737:chemistry*; D020128:Inhibitory Concentration 50; D010936:Plant Extracts / Q000494:pharmacology; D013729:Terpenes / Q000378:metabolism; D016808:Tetrahymena thermophila / Q000187:drug effects* / Q000201:enzymology / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D010936:Plant Extracts; D013729:Terpenes; D017869:Cyclic GMP-Dependent Protein Kinases