SHORT-TERM TISSUE DISTRIBUTION, DEPURATION AND POSSIBLE GENE-EXPRESSION EFFECTS OF [H-3] TCDD EXPOSURE IN SOFT-SHELL CLAMS (MYA ARENARIA)

A short-term, waterborne exposure and depuration study of Mya arenaria to [H-3]tetrachlorodibenzo-p-dioxin([H-3]TCDD) was performed. Gill, d igestive gland, foot, and gonad were sampled up to 2 weeks after a 24- h exposure to a low dose (10 parts per trillion [pptr]) or high dose ( 2,000 pptr) of [H-3]TCDD in the water. In the gill, peak concentration s occurred at the beginning of depuration (406 and 8,658 pg/g wet weig ht, low-and high-dose groups, respectively), whereas peak concentratio ns in the digestive gland and foot were found 12 to 24 h after exposur e (digestive gland, 539 and 9,369 pg/g wet weight; foot, 146 and 2,718 pg/g wet weight; low-and high-dose groups, respectively). In contrast , tissue concentrations in the gonad increased through the postexposur e period; at 2 week after exposure, tissue concentrations were highest in the gonad (243 and 3,012 pg/g wet weight, low- and high-dose group s, respectively). Examination of gill and gonad by differential displa y polymerase chain reaction identified potential alterations in expres sion of genes that may be associated with increased cell cycling or tr anslation initiation. This study shows that M. arenaria fan accumulate TCDD in the gonad from an acute exposure, and it identifies several M . arenaria genes whose expression may be altered by TCDD exposure.