Glutathione‐dependent detoxifying enzymes in rainbow trout liver: Search for specific biochemical markers of chemical stress

Abstract

Activities of trout liver microsomal glutathione S‐transferase (GST) and a series of cytosolic glutathione‐dependent detoxifying enzymes were determined after a single intraperitoneal treatment with phenobarbital, 2,2‐bis (p‐chlorophenyl)‐1,1‐dichloroethane (p,p′‐DDE), 2,3,‐dimethoxynaphthoquinone (NQ), or 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD). This study aimed to find xenobiotic‐specific parameters applicable as biochemical markers of the impacts of the prototypal xenobiotics. The effects of xenobiotics on cytosolic GST activities were substrate dependent. The rate of conjugation of p‐nitrobenzyl chloride was significantly induced by higher doses of p,p′‐DDE or NQ. The conjugation of ethacrynic acid was enhanced by phenobarbital, p,p′‐DDE, and NQ (i.e., by xenobiotics that do not induce cytochrome P4501A forms). The GST activity against 1,2‐epoxy‐3‐(p‐nitrophenoxy)propane was induced only by phenobarbital and by lower doses of p,p′‐DDE. The cytosolic GST activity, measured with 1‐chloro‐2,4‐dinitrobenzene as a substrate, was only weakly increased by phenobarbital, TCDD, higher doses of p,p′‐DDE, or by NQ at the lowest dose of 1 mg/kg. Although the latter activity is frequently used as a biomarker in ecotoxicology, various factors (including its weak inducibility) indicate that this biochemical parameter is probably not a suitable indicator of contamination in fish. Similarly, cytosolic glutathione peroxidase was not affected by the prototypal xenobiotics and appeared to be an unsuitable bioindicator of oxidative impacts of the tested compounds. On the other hand, microsomal GST activity was nonspecifically increased by phenobarbital, NQ, TCDD, and high doses of p,p′‐DDE. Glutathione reductase, another potential biomarker of oxidative stress, was induced by phenobarbital, NQ, and, to a lesser extent, p,p′‐DDE; therefore it appeared to be a less sensitive indicator to the exposure to prototypal xenobiotics than the microsomal GST. We conclude that the increase of microsomal GST and cytosolic glutathione reductase activities could become useful biochemical markers of oxidative stress, while the induction of cytosolic GST activities toward ethacrynic acid and probably also toward p‐nitrobenzyl chloride appear to hold promise as biochemical markers of specific impacts of p,p′‐DDE and redox cycling quinones in trout liver.

In vitro kinetics of hepatic glutathione s‐transferase conjugation in largemouth bass and brown bullheads

“…Glutathione S ‐transferase‐ethacrynic acid activities for largemouth bass (9–11 nmol/min/mg) and brown bullheads (16–18 nmol/min/mg) were lower than those reported for channel catfish (37 nmol/min/mg) and for rainbow trout ( Oncor‐hynchus mykiss ; 44 nmol/min/mg) but higher than those in brook trout ( Salvelinus fontinalis ; <0.1 nmol/min/mg) and bluegill sunfish (6.6 nmol/min/mg) [5,12]. The GST‐NBC activities reported here for brown bullheads (35–36 nmol/min/mg) and largemouth bass (24–28 nmol/min/mg) are higher than those reported by Petrivalsky et al [13] for rainbow trout (10 nmol/min/mg). In rats, NBC is preferentially conjugated by rGSTT1 and also rGSTM1 and rGSTM2 isozymes, but in rainbow trout, GST‐NBC is likely conjugated by a π‐class GST, the major GST isoform in trout liver [14].…”

Differential induction of glutathione S‐transferases in the clam ruditapes decussatus exposed to organic compounds

“…The doses of contaminants were chosen by comparison of experiments reported in the literature. Petrivalsky et al [6] conducted 48‐h rainbow trout exposures by intraperitoneal (i.p.) injection of 2 to 200 μg p,p′ ‐DDE/g and 80 μg PB/g to induce GST activities in the fish livers.…”

“…The activity of glutathione S‐transferases (GSTs) has been shown to increase in organisms as a function of xeno‐biotic concentration in the medium. Induction has been shown in vivo in the rainbow trout Oncorhyncus mykiss [6], in mol‐lusks [7], and in other invertebrates such as crabs [8]. Moreover, GST induction has been confirmed in the field by authors working on either organisms collected from polluted areas [8–11] or caged organisms [12].…”

Morphological alterations in the liver of yellow perch (Perca flavescens) from a biological mercury hotspot

“…Various effects of chronic dietary MeHg exposure are documented in laboratory and field studies of fish from highly contaminated areas. These include decreased growth (Friedmann et al 1996), impaired gonadal development (Friedmann et al 1996;Kidd and Batchelar 2011), oxidative damage through the production of reactive oxygen species (Zaman and Pardini 1996), and histological alterations in the liver and kidney such as an increase in macrophage aggregates (MAs) (Giari et al 2008;Mela et al 2007;Raldúa et al 2007). From such studies, a whole-body Hg threshold effect level of 0.2 μg g −1 wet weight (wet wt) has been proposed which is presumed to be protective of fish health (Beckvar et al 2005).…”