In Vivo and in Vitro Isomer-Specific Biotransformation of Perfluorooctane Sulfonamide in Common Carp (Cyprinus carpio)

Abstract

Biotransformation of PFOS-precursors (PreFOS) may contribute significantly to the level of perfluorooctanesulfonate (PFOS) in the environment. Perfluorooctane sulfonamide (PFOSA) is one of the major intermediates of higher molecular weight PreFOS. Its further degradation to PFOS could be isomer specific and thereby explain unexpected high percentages of branched (Br-) PFOS isomers observed in wildlife. In this study, isomeric degradation of PFOSA was concomitantly investigated by in vivo and in vitro tests using common carp as an animal model. In the in vivo tests branched isomers of PFOSA and PFOS were eliminated faster than the corresponding linear (n-) isomers, leading to enrichment of n-PFOSA in the fish. In contrast, Br-PFOS was enriched in the fish, suggesting that Br-PFOSA isomers were preferentially metabolized to Br-PFOS over n-PFOSA. This was confirmed by the in vitro test. The exception was 1m-PFOSA, which could be the most difficult to be metabolized due to its α-branched structure, resulting in the deficiency of 1m-PFOS in the fish. The in vitro tests indicated that the metabolism mainly took place in the fish liver instead of its kidney, and it was mainly a Phase I reaction. The results may help to explain the special PFOS isomer profile observed in wildlife.

Effect of hydro-oleophobic perfluorocarbon chain on interfacial behavior and mechanism of perfluorooctane sulfonate in oil-water mixture

“…PFOS has unique physicochemical and biological properties56, which may directly affect its transport and fate in aquatic environments as well as their removal efficiency from water. Conventional organic pollutants tend to accumulate in fat tissues of human bodies or animals, while PFOS is prone to accumulate in kidney, liver and serum789. It is the oleophobic perfluorocarbon chain that drives PFOS to stay away from fat tissues, while sulfonic group of PFOS may interact with the positively charged amino group in kidney or serum6101112.…”

<i>In vitro</i> metabolism of pesticides and industrial chemicals in fish

“…80) The succeeding intramolecular rearrangement of 1-hydroxymethyl-1-methylethyl to 2-hydroxy-2-methylpropyl was reported as a major secondary reaction for fenproximate. 104) Hydrolysis of an ester linkage was observed for parathion 80) and trans-permethrin, 83,103) most likely by esterases, and the cleavage of ether 107) and sulfonamide 110) linkages was reported, but with no information on the relevant enzymes. Examples of reductive metabolism are very limited for the debromination of hexabromocyclododecane (HBCD) 108) and the aniline formation from 3-trifluoromethyl-4-nitrophenol (TFN).…”

Brief Report

“…1 Perfluorooctane sulfonamide (PFOSA) is a breakdown product of higher molecular weight PFAS that are manufactured; PFOSA can also be synthesized directly and has been used in various products. 2 A previous investigation of time-trends of PFAS in Norway found the highest concentrations of PFOSA in the 1980’s and 1990’s and reported no significant correlation between serum concentrations of PFOSA with the more commonly studied PFAS: perfluorooctanoic acid (PFOA) or perfluoroctane sulfonic acid (PFOS). 3 Although the use of some PFAS has been phased out in many countries, exposure is ongoing and potential risks, including decreased fecundability, continue to be assessed.…”