Evaluation of Physiological and Genotoxic Effects of Arsenic on Rainbow Trout Fingerlings (Oncorhynchus mykiss)

AYELÉN GONZÁLEZ NUÑEZ; PAINEFILÚ, JULIO C.; BIANCHI, VIRGINIA A.; ANSELMO, MAILEN; PIGHIN, ANDRÉS; OSSANA, NATALIA; LUQUET, CARLOS MARCELO

Montevideo

Congreso; SETAC Latin America 15th Biennial Meeting; 2023

Society of Environmental Toxicology and Chemistry

Arsenic (As) is a natural contaminant widely distributed in surface waters either as AsIII or AsV, which may be toxic to aquatic such as the rainbow trout (Oncorhynchus mykiss), a farmed fish with commercial importance worldwide. The aim of this work was to evaluate the effect of AsIII on O. mykiss fingerlings. We performed in vivo, ex vivo, and in vitro assays using 240 fingerlings of 25.37 ± 0.5 mg and 1.84 ± 0.48 mm from the Center for Applied Ecology of Neuquén (CEAN). For the in vivo assays, we sorted the fingerlings in 4 glass flasks with 15 individuals each (2 control flasks and 2 flasks with 3.85 µM AsIII). After 48 h, we extracted the blood to determinate micronuclei (MN) and nuclear aberrations (NA) in erythrocytes. Also, we dissected gills, liver, foregut, posterior intestine, and caudal muscle, to determine the As bioaccumulation. For the in vitro assays, we used suspensions of isolated enterocytes pooled from 15 individuals. The enterocytes were incubated for 1 h at AsIII increasing concentrations from 0 to 7.7 µM AsIII. We analyzed the lysosomal membrane stability by recording the Neutral Red Retention Time of 50% of the cells observed (NRRT50). We evaluated the effect of AsIII over ATP-binding cassette transporters using the calcein efflux technique in intestine strips. For this purpose, the middle intestine was extracted, weighed, and incubated in glass tubes with AsIII increasing concentrations from 0 to 77 µM, plus 0.25 µM calcein-AM. As a result, we did not obtain differences for MN and NA between the two treatments at 48 h. We observed As bioaccumulation only in gills (0.46 µg As / g tissue) and muscle (2.77 µg As / g tissue). From a non-linear regression model NRRT50 vs. log AsIII concentration, we observed a concentration-dependent effect of AsIII on lysosome membrane stability, with an EC50 of 0.37 µM AsIII. We observed an AsIII concentration-dependent effect (IC50 = 5.48 µM AsIII) over the calcein transport rate in a non-linear regression model, wich indicate a competitive inhibition of ABCC transporters. All these results indicated that a) AsIII probably enters the O. mykiss organism through the gills, b) AsIII is also capable of entering the intestine cells since it causes deleterious effects observed in lysosomal membrane stability of enterocytes, c) no detection of As in the intestine probably reflects detoxification by ABCC toward the external medium or systemic circulation, and d) AsIII is accumulated in the muscle.