Details

Autor(en) / Beteiligte

• SCHULTZ, T. W
• TUCKER, V. A

Titel

Structure-toxicity relationships for the effects of N- and N, N'-alkyl thioureas to Tetrahymena pyriformis

Ist Teil von

• Bulletin of environmental contamination and toxicology, 2003-06, Vol.70 (6), p.1251-1258

Ort / Verlag

New York, NY: Springer-Verlag

Erscheinungsjahr

2003

Quelle

MEDLINE

Beschreibungen/Notizen

• Ecotoxicity testing with the freshwater ciliate Tetrahymena pyriformis allows for the examination of a sub-acute endpoint, population growth impairment, with a eucaryotic organism representative of the detrius food web (Larsen et al. 1997). Over the past two decades, Tetrahymena toxicity data have been used for the development and validation of structure-toxicity relationships for a variety of chemical classes (Schultz 1999; Cronin et al. 2001). Thioureas are sulfur-containing aliphatic diamines of the general formula R-NH-C(=S)-NH-R. Despite their use as herbicides (Schelenz and Kramer 1985), little is known about their ecotoxicity to non-target species. The presence of two nitrogen atoms in a thiourea more than counters the hydrophobic nature of the sulfur atom; the net result is a relatively hydrophilic compound. This property results in a propensity for the compound to reside in the aqueous phase. In theory, this hydrophilicity should limit the toxic potency of thioureas. Initial evaluation of 1-methyl-2-thiourea and 1-phenyl-2-thiourea revealed them to have population growth impairment to T. pyriformis in excess of that expected if the chemicals act as baseline toxicants. These observations spurred evaluation of a congeneric series of alkyl-thioureas. The purpose of this study was to examine the aquatic toxicity of selected thioureas. The specific aims were: (1) to determine the toxic potency for each thiourea in the T. pyriformis population growth impairment assay; (2) to develop a hydrophobic-dependent structure-toxicity model; (3) to compare this model to the baseline narcosis and amine narcosis models, and (4) to examine the T. pyriformis population growth kinetics of 1-methyl-2-thiourea.