RESUMO
The level of cytochrome P450 1A (CYP1A) in fish is used as a typical environmental biomarker for the presence of organic contaminants. We used RT-qPCR to investigate CYP1A mRNA levels in the liver, gill and gonopodium of guppies Jenynsia multidentata and Phalloceros caudimaculatus in wetlands within the Rio Grande city (RG) which is under the influence of the Patos Lagoon Estuary (RS, Brazil). The CYP1A mRNA levels evaluated in fish liver from two locations that receive non-treated wastewater effluents (S3 and S4) and another locations near an oil refinery (S6) and an industrial complex (S7), were higher than in locations remote from those sites (S1, S2 and S5). The sum of 16 priority PAHs in sediment confirmed high levels in S4 and S6 (3914.0 and 4414.0 ng g(-1) dw, respectively) comparing to S7>S2>S3>S5>S1 (119.3, 66.3, 62.8, 16.4 and 1.7 ng g(-1) dw). J. multidentata from sites S1 to S4 that were transferred to the laboratory exhibited CYP1A induction after 24 h waterborne exposure to 1 µM betanaphtoflavone (BNF) in all organs compared to controls, except in the liver of fish from site S4. This lack of CYP1A induction by BNF indicates a CYP1A refractory phenotype in guppy. Although this characteristic possibly involves the alteration in AHR signaling or control, the mechanism of resistance is unknown. The present study provides information about the use of the use of CYP1A in South American guppies as an useful biomarker tool for environmental contamination studies.