Time- and dose-dependence of hepatic mixed function oxidase activity in brook trout Salvelinus fontinalis on polychlorinated biphenyl residues: Implications for ‘biological effects monitoring’

Effects of the fungicide prochloraz on xenobiotic metabolism in rainbow trout: inhibition in vitro and time course of induction in vivo

1. Interactions between the fungicide prochloraz and the hepatic cytochrome P-450 of rainbow trout were studied by determination of enzymic activities in vitro using the microsomal fraction, and by kinetic studies. 2. Prochloraz inhibited 7-ethoxyresorufin-O-deethylase (EROD) in vitro. This inhibition was partially non-competitive: the enzyme-substrate-inhibitor (ESI) complex was catalytically active (68% of the activity of the enzyme-substrate complex). 3. Prochloraz in vitro inhibited aldrin epoxidase (AE) by a linear mixed-type mechanism. This inhibition might be high because of high affinity for prochloraz and lack of catalytic activity of the ESI complex. 4. Effects of prochloraz in vivo were studied as a function of time after intraperitoneal injection. Total cytochrome P-450 increased for more than 21 days. 5. EROD increased slightly at day 4 and then returned to control level. Kinetics showed an increase in apparent Km and Vmax. AE was strongly inhibited at day 4 (large increase in apparent Km) and then returned to control level in 21 days. 6. Spectral interactions with aniline showed strong inhibition and recovery to an activated level at day 21.

Effects of the fungicide prochloraz on xenobiotic metabolism in rainbow trout: in vivo induction

1. Rainbow trout were dosed with prochloraz by i.p. injection of sprayed food pellets. Cytochrome P-450, two P-450-dependent activities, and two conjugase activities were measured in vitro in microsomal or cytosolic fractions. 2. Prochloraz increased cytochrome P-450 in liver, intestine, and pyloric caeca: maximum response occurred at 30-100 mg/kg i.p. In cold conditions, this increase persisted for more than 8 days after injection. 3. Hepatic 7-ethoxycoumarin-O-dealkylase (ECOD) and 7-ethoxyresorufin-O-dealkylase (EROD) were inhibited by prochloraz except in one assay in warm water where they increased. In intestine and pyloric caeca, ECOD and EROD were not detected, even when cytochrome P-450 was increased. 4. UDP-glucuronosyltransferase (1-naphthol as substrate) was unchanged or inhibited after prochloraz dosing. 5. Glutathione-S-transferase (o-dinitrobenzene as substrate), was unchanged or inhibited by prochloraz. 6. The measured level of enzymic activities was the result of induction and inhibition by prochloraz residues. Variations in basal activities and perhaps in prochloraz interactions were due to temperature acclimatization.

Review and perspective on the use of mixed-function oxygenase enzymes in biological monitoring

It is often suggested that changes in simple biochemical/physiological responses may be useful for predicting the impacts of pollutants at population and community levels of biological organization. There are serious conceptual constraints to such a thesis and its seems likely that such simple responses can go no further than serving as early warning systems for delineating potential areas of pollutant impact--areas which (if shown to be significant in size) can then be subjected to more detailed population and community type studies. Environmental testing is a prerequisite for any response suggested to have value as a biological monitoring index and the induction of mixed-function oxygenase (MFO) enzymes has now been validated in a large number of field studies worldwide. Investigations have progressed from documenting induction near localized sources of hydrocarbon contamination to more diffuse sources of mixed organic pollution originating from industrial and domestic sources. Studies in the Great Lakes and Europe have demonstrated that the induction of MFO enzymes is a biological response of sufficient sensitivity to discriminate water quality differences over broad geographical areas. We suggest that as an early warning system, the induction of these enzymes can fulfill the requirement of "most sensitive biological response" for assessing a variety of organic pollution conditions. Given the high level of sensitivity of the MFO enzyme response, negative as well as positive field trials can be of value in addressing concerns about the toxicological significance of "high-profile" chemicals (and potent inducers) such as polycyclic aromatic hydrocarbons and organochlorines. MFO enzyme induction can also be an economical tool for environmental managers for reacting to real or perceived concerns about pollution such as effects on commercial fish stocks at sites of petroleum hydrocarbon development in the oceans.

Monitoring of cyclic organochlorines in the marine environment

Cyclic organochlorines are highly hydrophobic chemicals which usually possess a high persistence to microbial breakdown. These behavioural aspects determine the suitability of each environmental compartment for monitoring purposes, which is discussed.It is concluded, that monitoring of (cyclic) organochlorines should only be executed for compounds about which solid information is available on their environmental behaviour in abiotic and biotic environmental compartments. Under these conditions benthic invertebrates which use glycogen as their main energy-depot, appear to be the most suitable tool for environmental monitoring of lipophilic compounds. Concentrations should be expressed on the basis of (total) extractable lipids.The organisms to be compared should be sampled at a time when they have a similar physiological condition. This does not automatically mean synoptic sampling.Multi-component mixtures, such as PCB's, should be monitored on the basis of (selected) individual components in order to account for differences in behaviour of each component between different environmental compartments and animal species.Some representatives of the compounds discussed are strong inducers of mixed function oxygenase (MFO) enzyme systems. Therefore it should be investigated, if monitoring of MFO activity in addition to concentrations can be regarded as an early warning system of additive effects.