Tissue-Specific Uptake, Depuration Kinetics, and Suspected Metabolites of Three Emerging Per- and Polyfluoroalkyl Substances (PFASs) in Marine Medaka

Abstract

Restrictions on legacy per- and polyfluoroalkyl substances (PFASs) have led to the widespread use of emerging PFASs. However, their toxicokinetics have rarely been reported. Here, tissue-specific uptake and depuration kinetics of perfluoroethylcyclohexanesulfonate (PFECHS) and 6:2 and 8:2 chlorinated polyfluoroalkyl ether sulfonates (Cl-PFESAs) were studied in marine medaka (Oryzias melastigma). The fish were exposed to these substances for 28 days (0.2 μg/L), followed by a clearance period of 14 days. The depuration constant (k d) of PFECHS [0.103 ± 0.009 day–1 (mean ± standard deviation)] was reported for the first time. Among the six studied tissues, the highest concentrations of 6:2 Cl-PFESA, 8:2 Cl-PFESA, and PFECHS were found in the liver [1540, 1230, and 188 ng (g of wet weight)−1, respectively] on day 28 while the longest residence times were found in the eyes (t 1/2 values of 21.7 ± 4.3, 23.9 ± 1.5, and 17.3 ± 0.8 days, respectively). No significant positive correlation was found between the bioconcentration factors of the studied PFASs and the phospholipid or protein contents in different tissues of the studied fish. Potential metabolites of Cl-PFESAs, i.e., their hydrogen-substituted analogues (H-PFESAs), were identified by time-of-flight mass spectrometry. However, the biotransformation rates were low (<0.19%), indicating the poor capacity of marine medaka to metabolize Cl-PFESAs to H-PFESAs.

Size-Dependent Uptake and Depuration of Nanoplastics in Tilapia (Oreochromis niloticus) and Distinct Intestinal Impacts

“…When the tilapia were transferred to clean water, the depuration rate constant was determined by fitting the first-order model C t = C 0 · exp (− k d · t ) and the residual rate (%) was calculated by the equation Residual = 100 × C t / C 0 , where k d is the depuration rate constant (day –1 ), t is the depuration time (day), and C t and C 0 are the NP concentrations in fish tissue (mg/kg) at time t and the beginning of depuration, respectively. The depuration half-life ( t 1/2 ) of NPs was calculated according to the equation t 1 / 2 = ln nobreak0em.25em⁡ 2 / k normald The uptake rate constant ( k u ) was determined using a nonlinear regression with the equation C normale = ( k u · C s k d ) 0.25em [ 1 − exp false( prefix− k normald · t false) ] where k u is the uptake rate constant (L kg –1 day –1 ) and C s is the concentration of NPs in water (mg/L) . The tissue burden was calculated by the equation burden = C tissue × M tissue where C tissue (mg/kg) is the mean concentration of NPs in fish tissue at a certain time point and M tissue (kg) is the mean weight of fish tissue.…”

“…where k u is the uptake rate constant (L kg −1 day −1 ) and C s is the concentration of NPs in water (mg/L). 41 The tissue burden was calculated by the equation…”

Enantiospecific Uptake and Depuration Kinetics of Chiral Metoprolol and Venlafaxine in Marine Medaka (Oryzias melastigma): Tissue Distribution and Metabolite Formation

“…The depuration rate constant ( k d , day –1 ) was calculated by fitting the concentration during the clearance period to the following first-order model , ln ( C medaka ) = ln nobreak0em.25em⁡ C 0 − k normald t where C medaka is the growth-corrected whole-body concentration of the individual analytes, t is the depuration time (day), and C 0 is a constant. The depuration half-life ( t 1/2 , day) was defined as t 1/2 = ln 2/ k d …”

“…The depuration half-life (t 1/2 , day) was defined as t 1/2 = ln 2/k d . 32 The uptake rate constant (k u , L g −1 day −1 ) was calculated using the following nonlinear regression equation 8,31…”

Per- and Polyfluoroalkyl Substances (PFASs) Impair Lipid Metabolism in Rana nigromaculata: A Field Investigation and Laboratory Study

“…Per- and polyfluoroalkyl substances (PFASs) are a group of anthropogenic organic chemicals with fluorocarbon-based characteristics but different functional end groups . Due to their excellent chemical properties, PFASs have been applied for over 70 years in industrial and household products and appear to have high environmental persistence and biomagnification potential. , Among them, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) are the most abundant legacy PFASs found in environmental matrices, biota, and human tissue .…”