Induction of carboxylesterase and GST activity in rainbow trout Oncorhynchus mykiss by water soluble fraction obtained from a natural petroleum spill

LEGGIERI LEONARDO RAMÓN; DE ANNA JULIETA SOLEDAD; HERBERT LUCILA; KRISTOFF GISELA; LUQUET CARLOS MARCELO

Buenos Aires

Congreso; 11th SETAC Latin America Biennial Meeting "The role of science in environmental decision‐making"; 2015

SETAC Argentina

A natural petroleum spill affects Las Minas stream (41°17´21´´S, 71°10´58´´W, Río Negro Argentina), in which the rainbow trout, Oncorhynchus mykiss, is abundant throughout the year. We assayed possible biomarkers of exposure to polycyclic aromatic hydrocarbons (PAH): carboxylesterase (CEs) activity (induced PAH in rat liver) and glutathione S-transferase (GST) activity (sensitive to various pollutants). Our aim was to determine the effects of petroleum water soluble fraction (WSF) on O. mykiss liver and gill CEs and GST. WSF was prepared as 4.75 g crude petroleum (obtained from the spill) per L of river water. Juvenile fish (3.5 +- 0.6 g) were exposed to 5% WSF (237 mg L-1) for 24h (n = 8) and 96h (n = 8), using the same number of fish as control. Gills and liver were homogenized and the 11000 x g, 15 min supernatants were used for enzyme activity measurements. CEs activity was determined using p-nitrophenylacetate (p-NFA) and p-nitrophenylbutirate (p-NFB) as substrates, reading absorbance at 400 nm for 1 min. GST activity was measured according to Habig et al. (1974) reading absorbance at 340 nm for 5 min. Protein concentration, determined through Bradford´s method, was used to calculate enzyme specific activities. In all the groups, CEs activity measured with the substrate p-NFA was higher than the obtained using p-NFB (10.9 +- 3.8 vs. 8.1 +- 3.7 nmol/ min/mg protein). In liver of exposed fish, CEs activity measured with the substrate p-NFA was higher than in control fish, both at 24h and 96h. In contrast, there was no significant difference between treatments when p-NFB was used. In gills, CEs activity did not change at 24 h of exposure to WSF respect to the control but was increased at 96 h, irrespectively of the substrate used. However, the response observed at 96 h was higher when p-NFA was the substrate (77%) compared with the obtained with p-NFB (25%). In general, GST activities ranged from 13 to 105 nmol/min/mg protein. Liver GST activity was induced by exposure to WSF at 24h (68%) and at 96h (123%), while gill GST activity increased only at 96h (70%). This indicates that O. mykiss liver CEs (measured with p-NFA as substrate) and GST activities are sensitive biomarkers for oil contamination. Gill CEs and GST activities could be useful as biomarkers of PAH effects but only for detecting more prolonged exposure.