Accumulation and elimination kinetics of free and total (free plus protein-bound) microcystin-LR in the common carp Cyprinus carpio

Microcystins (MCs) are widespread hepatotoxins produced by several genera of freshwater cyanobacteria. After ingestion of cyanobacteria or contaminated water or food, MCs accumulate in aquatic organisms and are present in their cells as a free available fraction and as a fraction covalently bound to proteins, mainly phosphatase proteins that they inhibit. MCs are toxic to humans and animals and the related intoxications can cause symptoms of varying intensity ranging from gastroenteritis to kidney and liver failure, sometimes even death. It is therefore essential to monitor these toxins both in the environment and in exposed species, including fish. In this study, both total (free plus protein-bound) and free accumulation fractions of MCs were monitored in carp orally exposed on a daily basis (by voluntary feeding) to pure microcystin-LR during a period of 7 days followed by a elimination period of 21 days. The accumulation of total toxins in carp muscles was determined using Lemieux oxidation, although free microcystins fraction were determined by methanolic extraction and both fractions were analyzed by LC-MS/MS. Here will be presented the optimization of the Lemieux oxidation procedure on fish muscle matrix and the kinetics of free and of total MCs (measured by Lemieux oxidation).