ToxSci Advance Access published online on October 20, 2008
Toxicological Sciences, doi:10.1093/toxsci/kfn212
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Published by Oxford University Press 2008.
Physical-chemical and solvent considerations in evaluating the influence of carbon chain length on the skin sensitization activity of 1-bromoalkanes
Allergy and Clinical Immunology Branch, National Institute for Occupational Safety and Health, 1095 Willowdale Rd, MS 4020, Morgantown, West Virginia, 26505, 304 285-5720
Corresponding Author E-mail: pds3{at}cdc.gov
Received August 13, 2008; revision received September 25, 2008; accepted September 25, 2008
| Abstract |
|---|
The murine local lymph node assay (LLNA) is an internationally accepted assay for identification of contact allergens. The LLNA has also been used in research studies to evaluate contact allergen potency, as well as chemical structural – allergenic activity relationships. The 1-bromoalkanes have been used in such a manner as they represent a chemical series with generally the same chemical reactivity, but differing in alkane carbon-chain length dependent lipid solubilities. Previous reports noted a biphasic LLNA response with increasing carbon chain length that peaked at the 16 carbon-chain (C16) of 1-bromohexadecane (delivered in an acetone-olive oil vehicle, AOO; 4:1). In the present study, this biphasic LLNA response was confirmed and 1-bromoalkane chemical-physical factors were explored using both modeling tools and further laboratory studies to help understand this finding. Volatility and effect of vehicle on 1-bromoalkanes sensitizations were assessed. Select 1-bromoalkanes were tested in the LLNA using the polar, protic vehicle, tetrahydrofuran-butanol (THF-BuOH; 1:1) to compare to the nonpolar (aprotic) vehicle AOO 1-bromoalkanes-LLNA responses. Enhanced 1-bromoalkane LLNA responses were observed using the THF-BuOH vehicle, but with the greatest activity still observed for 1-bromohexadecane (C16). The shorter 1-bromoalkanes were subject to volatile losses upon application with approximately 75% volatile loss from a surface of 1-bromohexane (C6) within 5 min at room temperature. It is concluded that multiple factors, in addition to lipid solubility, including vehicle, solvation, and retention on the skin surface contribute to the apparent potency of 1-bromoalkanes in the LLNA.