Abstract

Emamectin benzoate (EMB) is one of the drugs used for the treatment and control of infections by Caligus rogercresseyi on salmonids. EMB is orally delivered to the salmon in food, which could be affecting the activity of biotransformation markers in these fish. The aim of this study was to determine the effect of EMB treatment on the mRNA and protein expression levels and enzymatic activity of cytochrome P450 1A (CYP1A), flavin-monooxygenase (FMO) and glutathione S-transferase (GST) in different tissues of rainbow trout (Oncorhynchus mykiss). Rainbow trout were collected between 10 and 25 days after completion of medication with EMB by a standard seven-day treatment in different salmon farms from southern Chile. The CYP1A, FMO and GST mRNA, protein levels and activity in the liver, muscle, gill, kidney and intestine tissues from rainbow trout were measured. Most mRNA and protein levels were significantly affected by treatment with EMB. The highest mRNA transcriptional up-regulations were observed with CYP1A in the liver and FMO in the liver, muscle and kidney and were very marked with regard to the increases of CYP1A and FMO in the gill and GST in the gill and intestine. These effects only correlated slightly with FMO protein levels in the liver muscle and gill. The highest up-regulations for protein levels were observed for GST in the kidney. While, the down-regulation measured in CYP1A was similar between protein levels in the liver, gill and intestine, and also in CYP1A activity levels in all tissues examined. On the other hand, GST mRNA levels were essentially without great changes, except slight increases in the gill and intestine, while GST protein and activity levels increased in all tissues measured. These results show that treatment with EMB induces changes of the expression of detoxification enzymes in most trout tissues, and this effect was consistent with increases of activity for FMO in the intestine and was comparable to the increases of activity for GST observed in all trout tissues analyzed. By contrast, EMB decreased the CYP1A activity levels in all tissues examined. These results show that treatment with EMB in trout alters the expression and activity of CYP1A, FMO and GST, which could be affecting detoxification processes and immunomodulatory mechanisms. Moreover, the data obtained will allow insight into the mechanisms involved in the biotransformation of EMB in salmonids and its putative relation with drug resistance observed in EMB treatments. (C) 2014 Elsevier B.V. All rights reserved.