China
Africa
Explore chapters and articles related to this topic
Uptake, Accumulation, Biotransformation, and Excretion of Xenobiotics
Published in Alan G. Heath, Water Pollution and Fish Physiology, 2018
Van Veld (1990) has reviewed the processes involved in absorption of xenobiotics from the digestive tracts of fish. The proximal portion of the intestine is where most of the food absorption occurs and the pyloric ceca, if present, add absorptive surface area. Lipophilic toxicants are assimilated in much the same way as dietary fat. The lipids (and toxicants) are first digested by pancreatic lipase and bile salts yielding a fine suspension of micelles which are colloidal particles of fatty elements clustered together with bile salts in such a way as to facilitate their diffusion through the aqueous phase. The presence and digestion of dietary lipids actually facilitates the accumulation of toxicants (Van Veld, 1990), perhaps by stimulation of bile and/or lipase secretion. Passage into the intestinal enterocytes occurs presumably by diffusion of the fatty materials from the micelle, but absorption of some materials such as fatty acids may be facilitated by a protein carrier.
Potential adverse health effects of ingested micro- and nanoplastics on humans. Lessons learned from in vivo and in vitro mammalian models
Published in Journal of Toxicology and Environmental Health, Part B, 2020
Laura Rubio, Ricard Marcos, Alba Hernández
Absorption of nutrients and chemicals is a process common to all mammalian species. Therefore, mice, rats, hamsters, and guinea pigs were historically used for absorption and toxicokinetic studies (OECD 2010). However, the vast combination of possible physicochemical properties seen in this heterogeneous mixture of MPs and NPs makes the use of in vivo mammalian models difficult to specifically assess absorption distinct from other parameters. In this context, in vitro models are commonly employed and recommended for practical, cost-effective and ethical reasons. Among the different cell lines available, as representative of the human small intestine, differentiated Caco-2 cells are the most widely used (Neutra and Louvard 1989; Zweibaum et al. 1991). These cells, representing enterocytes (the most abundant epithelial cell type in the intestine) growing on a semi-permeable membrane, may be utilized to assess the absorption of the compound from the apical to the basolateral chamber (Lefebvre et al. 2015). In addition, the establishment of co-cultures of Caco-2 along with HT-29 cells, as a cell model for mucus secretion, and with the lymphocytic Raji-B cells, as cells able to transform Caco-2 cells into the “M” cells characteristics of Payer’s patches, represents an in vitro physiological/structural model of the intestinal barrier. The structure of this in vitro model is indicated in Figure 1. This model was successfully employed in many pharmacological and toxicological investigations, and commonly used for assessing the effective translocation of nanomaterials (García-Rodríguez et al. 2018; Vila et al. 2018). Thus, this model was proposed for the study of MPs and NPs absorption, including cell uptake and translocation through the intestinal barrier.