title: Single-dose topical exposure to the pyrethroid insecticide, permethrin in C57BL/6N mice: effects on thymus and spleen.
abstract: Immunomodulatory effects of single topical exposure to permethrin were evaluated in 5-week-old female C57BL/6N mice. Mice exposed to 5-25 microl permethrin (equivalent to 220-1100 mg/kg body weight) on shaved interscapular skin were evaluated for altered body weight; splenic and thymic organ weight and cellularity; thymocyte cell surface expression, cellular apoptosis; splenic macrophage phagocytosis and hydrogen peroxide production; splenic B cell antibody production and T cell cytolytic activity; and mitogen-induced proliferation of splenocytes and thymocytes after in vivo or in vitro permethrin exposure. Topical permethrin application (25 microl) caused 32% inhibition of splenic T cell proliferation; in vitro exposure to permethrin also diminished splenocyte proliferation by 72% at 25 microM and 86% at 100 microM. permethrin did not appear to affect other leukocyte functional assays. Dose-related decreases in thymic cellularity of 52 and 80% were seen in mice exposed to 15 and 25 microl permethrin, respectively. Apoptosis was significantly increased in CD4(-)8(-) and CD4(-)8(+) thymocytes, and the CD4(+)CD8(+) thymocyte subpopulation was most severely diminished, suggesting possible chemical-induced apoptotic mechanism of thymic atrophy. Permethrin also caused splenic hypocellularity by 31% at 15 microl, and by 50% at 25 microl, an effect that may relate to inhibited proliferation or reduced seeding from the hypocellular thymus.
authors.affiliation: Department of Biomedical Sciences and Pathobiology, Virginia-Maryland Regional College of Veterinary Medicine, Virginia Polytechnic Institute and State University, Blacksburg 24061-0442, USA. mrprater@vt.edu
authors.forename: M R
authors.initials: MR
authors.lastname: Prater
authors.forename: R M
authors.initials: RM
authors.lastname: Gogal
authors.forename: B L
authors.initials: BL
authors.lastname: Blaylock
authors.forename: J
authors.initials: J
authors.lastname: Longstreth
authors.forename: S D
authors.initials: SD
authors.lastname: Holladay
mesh_terms: D000287:Administration, Topical; D000818:Animals; D000917:Antibody Formation / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects; D001402:B-Lymphocytes / Q000187:drug effects*; D002455:Cell Division / Q000187:drug effects; D005260:Female; D005434:Flow Cytometry; D006462:Hemolytic Plaque Technique; D007306:Insecticides / Q000008:administration & dosage / Q000633:toxicity*; D008163:Luminescent Measurements; D051379:Mice; D008810:Mice, Inbred C57BL; D009929:Organ Size / Q000187:drug effects; D026023:Permethrin / Q000008:administration & dosage / Q000633:toxicity*; D013154:Spleen / Q000187:drug effects* / Q000276:immunology / Q000473:pathology; D013601:T-Lymphocytes / Q000187:drug effects*; D013950:Thymus Gland / Q000187:drug effects* / Q000276:immunology / Q000473:pathology
chemical_list: D007306:Insecticides; D026023:Permethrin