Uptake of microcystin-RR and biotransformation response by Jenynsia multidentata (Pisces, Anablepidae).

CAZENAVE, J., WUNDERLIN, D.A., BISTONI, M.A., WIEGAND, C., PFLUGMACHER, S.

Buenos Aires

Congreso; VI Congreso SETAC Latinoamérica.; 2003

SETAC

The main goal of this study was to evaluate the uptake as well as effects of the cyanotoxin Microcystin-RR (MC-RR) on detoxication system of the fish Jenynsia multidentata. We decided to use this fish for testing because it is widely distributed in eutrophic lakes in the Province of Córdoba (Argentina), where MC-RR is present at relevant concentrations ranging from 7 to 1777mg.g-1DW. Thus, the study presents evidence on the response of biota to toxic stress caused by this cyanotoxin. Adult specimens were collected from a quasi-pristine site and acclimated in the laboratory. Fish were exposed to 0, 2, 5, 10 and 20 µgL-1 MC-RR. We evaluated the activitation of the biotransformation system measuring glutathione-S-transferase (GST) activity in both microsomal and soluble (cytosolic) fractions of  fish liver using 1-chloro-2,4-dinitrobenzene (CDNB) and fluorodifen as substrates. The uptake of MC-RR was evaluated in gills, livers, gall bladders, intestines and brains of fish exposed to 50µgL-1 MC-RR by MALDI-TOF mass spectrometry. The activity of soluble GST towards the substrate CDNB was significantly increased in fish exposed to 5 and 10 µgL-1 as compared with controls. Higher concentration of the toxin caused a reduction in enzyme activity. In contrast, microsomal GST did not present significant changes throughout the studied concentrations.The MALDI-TOF spectrum yield a main peak corresponding to MC-RR (m/z 1038) from gill, liver and brain samples of exposed fish. Results from MALDI-TOF gives clear evidences on the uptake of MC-RR by fish, while GST assays demonstrate activation of the biotransformation system of fish exposed to this cyanotoxin. The presence of MC-RR in brain rose questions on the biochemical transport (active or difusional) as well as on the neurological effect and changes in the behavior of exposed fish.