IDENTIFICATION OF DIOXIN-SPECIFIC BINDING-PROTEINS IN MARINE BIVALVES

Epidemiological investigations of germ cell tumors of Maine soft shell clams (Mya arenaria) and hard shell clams (Mercenaria spp.) from Flor ida demonstrate the prevalence of histogenically similar gonadal cance rs as high as 40 and 60%, respectively. Human mortality rates due to o varian cancer from the same areas are significantly greater than the n ational average. Since further investigation revealed that there was a heavy use of herbicides at these sites, we proposed to investigate th eir possible role in the etiology of the clam tumors. One avenue of in vestigation was to determine whether clams had a mechanism similar to the vertebrate Ah receptor which could be activated by halogenated aro matic hydrocarbons (HAH). We used the TCDD photoaffinity analog 125)-I ]-2-azido-3-iono-7,8-dibromodibenzo-p-dioxin to detect two cytosolic p roteins (28 and 39 kDa) in Mercenaria mercenaria and one (35 kDa) in M ya arenaria which specifically bound this ligand. Expression of both p roteins in Mercenaria is tissue specific with the highest levels obser ved in cytosols from gill and gonad. Females exhibit higher levels of the 39 kDa protein in gonadal tissue than do the males. Studies to det ermine the relationship of these proteins to vertebrate Ah receptors, as well as their possible role in gonadal tumor development, are in pr ogress. Cpyright (C) 1996 Elsevier Science Ltd