title: Comparison of two screening bioassays, based on the frog sciatic nerve and yeast cells, for the assessment of herbicide toxicity.
abstract: Two different test systems, one based on the isolated sciatic nerve of an amphibian and the other on a microbial eukaryote, were used for the assessment of herbicide toxicity. More specifically, we determined the deleterious effects of increasing concentrations of herbicides of different chemical classes (phenoxyacetic acids, triazines, and acetamides), and of 2,4-dichlorophenol (2,4-DCP), a degradation product of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), on electrophysiological parameters and the vitality of the axons of the isolated sciatic nerve of the frog (Rana ridibunda) and on the growth curve of the yeast Saccharomyces cerevisiae based on microtiter plate susceptibility assays. The no-observed-effect-concentration (NOEC), defined as the maximum concentration of the tested compound that has no effect on these biological parameters, was estimated. In spite of the different methodological approaches and biological systems compared, the NOEC values were identical and correlated with the lipophilicity of the tested compounds. The relative toxicity established here, 2,4-DCP > alachlor, metolachlor >> metribuzin > 2,4-D, 2-methyl-4-chlorophenoxyacetic acid (MCPA), correlates with the toxicity indexes reported in the literature for freshwater organisms. Based on these results, we suggest that the relatively simple, rapid, and low-cost test systems examined here may be of interest as alternative or complementary tests for toxicological assessment of herbicides.
authors.affiliation: Laboratory of Animal Physiology, Department of Zoology, School of Biology, Aristotle University, Thessaloniki 54124, Hellas, Greece.
authors.forename: Chrisovalantis
authors.initials: C
authors.lastname: Papaefthimiou
authors.forename: Maria de Guadalupe
authors.initials: Mde G
authors.lastname: Cabral
authors.forename: Christina
authors.initials: C
authors.lastname: Mixailidou
authors.forename: Cristina A
authors.initials: CA
authors.lastname: Viegas
authors.forename: Isabel
authors.initials: I
authors.lastname: Sá-Correia
authors.forename: George
authors.initials: G
authors.lastname: Theophilidis
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000633:toxicity; D000081:Acetamides / Q000633:toxicity; D000818:Animals; D001001:Anura; D001681:Biological Assay / Q000379:methods*; D002733:Chlorophenols / Q000633:toxicity; D006540:Herbicides / Q000633:toxicity*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000254:growth & development; D012584:Sciatic Nerve / Q000187:drug effects* / Q000378:metabolism; D013997:Time Factors; D014227:Triazines / Q000633:toxicity; D015003:Yeasts / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development
chemical_list: D000081:Acetamides; D002733:Chlorophenols; D006540:Herbicides; D014227:Triazines; C000188:alachlor; D015084:2,4-Dichlorophenoxyacetic Acid; C009235:metribuzin; C004762:2,4-dichlorophenol; C051786:metolachlor