Toxicity of dioxin: the function of the PAS proteins

Dioxin derivatives cause a major and diverse toxicity in rodents :while the ir effects on humans remain controversial. Some recent events show that a r isk for human exposure is obvious. A better understanding of the consequenc es of these chemicals on human biology; is needed. Until then, safety proce dures have to limit human exposure to a minimum. This document offers a pre sentation of this family of xenobiotics,their origins and their toxic effec ts on animal and cellular models compared to their consequences in some cas es of human exposure (<<Seveso>>). A molecular signaling pathway for most o f the biological effects of dioxin is described. It includes a pair of <<PA S>> - domain proteins: a dioxin-activated receptor (AHR) and its heterodime ric partner (Arnt). The resulting complex activates a battery of target gen es whose nature do not authorizes vet the full understanding of the toxicit y of dioxins. Null animal models were helpful in identifying some developme ntal and physiological implications of the dioxin-activated pathway.