Lack of constitutive and inducible ethoxyresorufin-O-deethylase activity in the liver of suckermouth armored catfish (Hypostomus affinis and Hypostomus auroguttatus, Loricariidae)

Abstract

We investigated the presence and inducibility of CYP1A in suckermouth catfish (Hypostomus affinis and Hypostomus auroguttatus, Loricariidae), tilapia (Oreochromis niloticus, Cichlidae) and mice (Mus musculus, Muridae). Alkoxyresorufin-O-dealkylases (EROD, MROD, PROD and BROD) were detected and proved to be inducible (beta-naphthoflavone, BNF or dimethylbenz[a]anthracene, DMBA, 50 mg/kg bw ip) in liver microsomes from tilapia and mice. In loricariids, alkoxyresorufin-O-dealkylases were either undetectable (MROD/EROD) or very low (PROD/BROD), and so they remained after treatment with BNF or DMBA. Ethoxycoumarin-O-deethylase (ECOD) was recorded in all species and proved not to be inducible by BNF or DMBA. In loricariids and tilapia, ECOD was not depressed by a concentration of alpha-naphthoflavone (CYP1A-inhibitor) that markedly depressed EROD in tilapia. A CYP1A-like protein was detected by a monoclonal antibody in rats, mice and tilapia, but not in loricariids. A polyclonal antibody, however, detected a CYP1A-like protein in liver microsomes of loricariids. Suckermouth catfish, rats, mice and tilapia express a protein reactive with a polyclonal antibody against trout CYP3A. Loricariids and tilapia exhibited marked genotoxic responses (enhanced incidence of micronucleated erythrocytes) following treatment DMBA (50 mg/kg bw ip), a promutagen activated by CYP1A/1B. Therefore, although not exhibiting EROD, a CYP1A-mediated activity, loricariids converted DMBA into its genotoxic metabolites. Our findings suggest that the CYP1A-like protein of locariid catfish recognizes DMBA, but not ethoxyresorufin, as a substrate.

Oxidative stress in Nile tilapia (Oreochromis niloticus) and armored catfish (Pterygoplichthys anisitsi) exposed to diesel oil

“…Although EROD activity was low in P. anisitsi, it was detected even in the control group. These results differ from other studies, whose authors did not observe EROD activity in two species of armored catfish, Hypostomus af f inis and Hypostomus auroguttatus, which were injected with naphtoflavone (NF) (Parente et al 2009). It is possible that, although EROD is not induced by NF in loricarides, it could be induced by other PAHs present in petroleum derivatives, even at relatively low levels of activity, when compared to tilapias.…”

Effects of pentachlorophenol on the detoxification system in white-rumped munia ( Lonchura striata )

“…5a), which is in accordance with the increase in EROD activity following exposure to PCP observed in quail hepatocytes (Verbrugge et al, 2001). Previous studies have revealed that BROD can be induced by phenobarbital, hexachlorobenzene, and PCBs (Li and Hansen, 1996;Parente et al, 2009;Smith et al, 1993). In the present study, however, BROD activity was not significantly different after PCP exposure.…”

Physiological response of alligator gar juveniles (Atractosteus spatula) exposed to sub-lethal doses of pollutants

“…Absence of EROD activity has also been reported in primitive fish such as the sea lamprey Petromyzon marinus (Hahn et al 1998), and the American paddlefish (Polyodon spathula) exposed to BNF (Gundersen et al 2000). The variability of EROD activity levels among species and populations (Parente et al 2009;Gundersen et al 2000) may contribute to explain the absence of activity in gar under the experimental conditions established in this research. On the other hand, a very low response of the CYP1A system has been registered in some species when individuals are exposed to inducing agents.…”

“…However, this would not be the first report of the absence of EROD activity in fish. Previously, the nonexistence of EROD activity was reported in three fish species of the Loricariidae family, both in wild and captive organisms induced with BNF and dimethylbenz [a] anthracene (Parente et al 2009). Absence of EROD activity has also been reported in primitive fish such as the sea lamprey Petromyzon marinus (Hahn et al 1998), and the American paddlefish (Polyodon spathula) exposed to BNF (Gundersen et al 2000).…”