title: Advantage of using CBA/N strain mice in a non-radioisotopic modification of the local lymph node assay.
abstract: The murine local lymph node assay (LLNA) is currently recognized as a stand-alone test method for determining the skin sensitizing potential of chemicals. It has been incorporated into the official test guidelines published by some authorities, including the OECD. To avoid the use of radioisotopes, efforts have been made recently to develop non-radioisotopic modifications of the LLNA. A non-radioisotopic modification of the LLNA was developed previously using 5-bromo-2'-deoxyuridine (BrdU) incorporation (non-RI LLNA). However, the non-RI LLNA was found to be somewhat less sensitive than the standard assay. This study reports the advantage of using mice of the CBA/N strain in the non-RI LLNA to improve the sensitivity of this method. The non-RI LLNA was performed using CBA/JN and CBA/N mice exposed to one of four confirmed skin sensitizers, 2,4-dinitrochlorobenzene (DNCB), eugenol (EG), isoeugenol (IEG) or alpha-hexylcinnamic aldehyde (HCA), and to one non-sensitizer, propylene glycol (PG). The EC3 values for DNCB, IEG, EG, HCA and PG were calculated to be 0.1%, 9.6%, 40.6%, 45.5% and >50% in CBA/JN mice and 0.08%, 1.9%, 10.7%, 20.3% and >50% in CBA/N mice, respectively. The EC3 values for DNCB, IEG, EG, HCA and PG in the standard LLNA using CBA/Ca mice and radioisotopes were reported elsewhere as being 0.08%, 1.3%, 13.0%, 8.0% and >50%, respectively. The EC3 values derived from the CBA/N mice in the non-RI LLNA were nearly equivalent to the EC3 values obtained using the standard radioisotopic LLNA with CBA/Ca mice. These data suggest that the use of CBA/N mice may provide a realistic opportunity to develop a version of the LLNA that does not have a requirement for the use of radioisotopes, but which nevertheless has sensitivity approaching, or comparable to, the standard method.
authors.affiliation: Hita Laboratory, Chemicals Evaluation and Research Institute, 3-822, Ishii-machi, Hita-shi, Oita 8770061, Japan. takeyoshi-masahiro@ceri.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Takeyoshi
authors.forename: Shuji
authors.initials: S
authors.lastname: Noda
authors.forename: Kanji
authors.initials: K
authors.lastname: Yamasaki
authors.forename: Ian
authors.initials: I
authors.lastname: Kimber
mesh_terms: D000171:Acrolein / Q000031:analogs & derivatives / Q000633:toxicity; D000485:Allergens / Q000633:toxicity*; D000818:Animals; D001973:Bromodeoxyuridine / Q000378:metabolism; D017449:Dermatitis, Allergic Contact; D004137:Dinitrochlorobenzene / Q000633:toxicity; D005054:Eugenol / Q000031:analogs & derivatives / Q000633:toxicity; D005260:Female; D007509:Irritants / Q000633:toxicity; D023441:Local Lymph Node Assay; D008198:Lymph Nodes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008808:Mice, Inbred CBA; D011237:Predictive Value of Tests; D013045:Species Specificity
chemical_list: D000485:Allergens; D004137:Dinitrochlorobenzene; D007509:Irritants; C080043:hexyl cinnamic aldehyde; D005054:Eugenol; C036643:isoeugenol; D000171:Acrolein; D001973:Bromodeoxyuridine