Receptor-mediated in vitro bioassay for characterization of Ah-R-active compounds and activities in sediment from Korea

Sediment extracts of stream sediments, collected from inland areas of Lake Shihwa (LSI) and Masan Bay (MBI), were screened for their abilities to induce aryl hydrocarbon receptor (Ah-R) mediated gene expression in vitro. Cell viability assay was also performed to examine cytotoxic effects on the Ah-R-mediated activities of sediment samples. Over 80% (30 out of 36) of sediment raw extracts (REs) induced significant Ah-R-mediated activities in the H4IIE-luc cell bioassays. Ah-R-mediated activities of sediment REs from LSI locations (mean=58%-TCDD-max; n=21) were greater than those of sediment REs from MBI locations (mean=35%-TCDD-max; n=15), in general. Seven (mean+/-SD=100+/-14%-TCDD-max) of 21 sediment REs from LSI showed Ah-R-mediated activities comparable to that (set to, 100%-TCDD-max) elicited by 1240 pM TCDD. Whereas, in MBI, only two REs from M1 (93%-TCDD-max) and M9 (82%-TCDD-max) showed significantly great responses that comparable to maximum response of TCDD standard curve. Sample potencies relative to the TCDD standard (TCDD-EQs) were estimated based on full dose-response characteristics of REs and TCDD-EQs were found to be 14-868 pg TCDD/g, dw and 17-275 pg TCDD/g, dw, in LSI and MBI, respectively. A range of TCDD-EQ20-80 of samples, based on multiple estimates of relative potency (REP20-80), did not vary greatly (2-4-fold) in the H4IIE-luc bioassays, which indicated relatively low degree of uncertainties in point estimates of REP for sediment REs examined. Acid-treatment of REs samples improved quantitative biological responses of samples followed by decreases in cytotoxicity identified by MTT cell viability assays.