Dexamethasone and 2,3,7,8-tetrachlorodibenzo-p-dioxin can induce thymic atrophy by different mechanisms in mice.
The effects of in vivo exposure to dexamethasone (DEX) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on thymocyte proliferation and thymocyte number were compared. In the thymus of DEX-treated mice (1 mg/kg) both proliferation and cell number had decreased by 70% one day after exposure. This decrease was, however, transient, and values returned to normal within 2 weeks. By contrast, in TCDD exposed mice (50 micrograms/kg), a reduction in proliferation was not observed until day 2 after exposure, and the degree of reduction was only about 50%. By this point in time, cell number had only decreased by 20%. Proliferation increased again on day 3 after TCDD administration, whereas cell number continued to decrease and remained low throughout the observation period (8 days). DEX had a direct and immediate effect on cells in all thymocyte subpopulations whereas TCDD initially only affected the immature double negative (DN) and double positive (DP) populations.
Lundberg
K
K
Department of Toxicology, Uppsala University, Sweden.
D000818:Animals; D001284:Atrophy; D001692:Biological Transport; D002455:Cell Division / Q000187:drug effects; D003907:Dexamethasone / Q000633:toxicity*; D007124:Immunoenzyme Techniques; D007700:Kinetics; D051379:Mice; D000072317:Polychlorinated Dibenzodioxins / Q000378:metabolism / Q000633:toxicity*; D013601:T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000473:pathology*; D013950:Thymus Gland / Q000187:drug effects / Q000473:pathology*
D000072317:Polychlorinated Dibenzodioxins; D003907:Dexamethasone