title: Suppression of humoral immune responses by 2,3,7,8-tetrachlorodibenzo-p-dioxin intercalated in smectite clay.
abstract: 2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a highly toxic environmental contaminant found in soils and sediments. Because of its exceptionally low water solubility, this compound exists predominantly in the sorbed state in natural environments. Clay minerals, especially expandable smectite clays, are one of the major component geosorbents in soils and sediments that can function as an effective adsorbent for environmental dioxins, including TCDD. In this study, TCDD was intercalated in the smectite clay saponite by an incipient wetness method. The primary goal of this study was to intercalate TCDD in natural K-saponite clay and evaluate its immunotoxic effects in vivo. The relative bioavailability of TCDD was evaluated by comparing the metabolic activity of TCDD administered in the adsorbed state as an intercalate in saponite and freely dissolved in corn oil. This comparison revealed nearly identical TCDD-induced suppression of humoral immunity, a well-established and sensitive sequela, in a mammalian (mouse) model. This result suggests that TCDD adsorbed by clays is likely to be available for biouptake and biodistribution in mammals, consistent with previous observations of TCDD in livestock exposed to dioxin-contaminated ball clays that were used as feed additives. Adsorption of TCDD by clay minerals does not appear to mitigate risk associated with TCDD exposure substantially.
authors: Department of Crop and Soil Sciences, Michigan State University, East Lansing, Michigan, USA. boyds@msu.edu
authors: Stephen A
authors: SA
authors: Boyd
authors: Cliff T
authors: CT
authors: Johnston
authors: Thomas J
authors: TJ
authors: Pinnavaia
authors: Norbert E
authors: NE
authors: Kaminski
authors: Brian J
authors: BJ
authors: Teppen
authors: Hui
authors: H
authors: Li
authors: Bushra
authors: B
authors: Khan
authors: Robert B
authors: RB
authors: Crawford
authors: Natalia
authors: N
authors: Kovalova
authors: Seong-Su
authors: SS
authors: Kim
authors: Hua
authors: H
authors: Shao
authors: Cheng
authors: C
authors: Gu
authors: Barbara L F
authors: BL
authors: Kaplan
mesh_terms: D000327:Adsorption; D000383:Agriculture; D000538:Aluminum Silicates / Q000737:chemistry*; D000818:Animals; D000077215:Clay; D004784:Environmental Monitoring; D052918:Environmental Restoration and Remediation; D005260:Female; D056724:Immunity, Humoral / Q000187:drug effects*; D007364:Intercalating Agents / Q000737:chemistry; D051379:Mice; D000072317:Polychlorinated Dibenzodioxins / Q000737:chemistry / Q000633:toxicity*; D018570:Risk Assessment; D017640:Silicates / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry / Q000633:toxicity*
chemical_list: D000538:Aluminum Silicates; D007364:Intercalating Agents; D000072317:Polychlorinated Dibenzodioxins; D017640:Silicates; D012987:Soil; D012989:Soil Pollutants; C099453:saponite; C033214:Smectite; D000077215:Clay