Submitochondrial particles as toxicity biosensors of chlorophenols

Abstract

An in vitro bioassay procedure was used to investigate the toxic action of chlorophenols on mitochondrial respiratory parameters The toxicity of these compounds was evaluated by determining their effects on the energy coupled reverse electron transfer (RET) in submitochondrial particles (SMPs) from beef heart mitochondria The bioassay procedure is based on the spectrophotometric recording of the effects of toxicants on the rate of NAD+ reduction, induced by ATP and succinate at the first site level of the respiratory chain The toxicity end point was expressed as the toxicant concentration that causes 50% inhibition of NAD+ reduction rate (EC50). The EC50 values determined for the 14 tested chlorophenols ranged from 17 mg/L for 2 chlorophenol to 0 081 mg/L for pentachlorophenol, indicating a general trend of increasing toxicity with increasing chlorine substitution Among chlorophenol isomers, which have the same number of chlorine atoms, a lesser toxicity was associated with ortho‐substituted chlorophenols, whereas meta substituted chlorophenols were much more toxic The EC50 values were compared with the toxicity data for a variety of bioassays, by means of linear regression analysis High degrees of correlation obtained with toxicity tests involving different freshwater species demonstrate the ability of SMPs to reproduce the toxic effects of the tested compounds upon aquatic organisms This supports the assessment that the respiratory chain is the main target of this class of toxicants Results obtained with chlorophenols and, in previous studies, with other environmental contaminants confirm the suitability of the SMP bioassay as a prescreening or complementary short term test for monitoring aquatic toxicity

Preliminary study to compare body residues and sublethal energetic responses in benthic invertebrates exposed to sediment‐bound 2,4,5‐trichlorophenol

“…Chlorophenols are pollutants that originate from pulp bleaching effluents, pesticide manufacturing, wood-preserving agents, and combustion ashes. They uncouple oxidative phosphorylation [4][5][6], thus disrupting the regulation of energy metabolism. The sublethal bioenergetic response caused by these toxicants can be detected at organism level by monitoring their rate of energy metabolism, e.g., heat dissipation, and the response should reflect the increased metabolic rate of the animal [7,8].…”

Repeatability of the Submitochondrial Particle Assay

“…The authors also reported a mean EC for zinc (as ZnSO ) in the RET assay of 1700$110 ppb (n"2; CV"6.5%) compared with a composite EC of 2100$190 g/L and a CV of 9.1% (as Zn) in this study. Argese et al (1995) assessed the reproducibility and stability of the SMP response during a 12-h working period by conducting eight tests with a stock solution of an unidenti"ed toxicant and the same SMP stock suspension. The authors reported that the response reproducibility of the SMP test was within a relative 95% CI of 7%, as calculated by applying the Student distribution to the EC values obtained by eight replicates.…”

“…The use of SMP as a surrogate in water quality assessments and aquatic toxicity testing has been promoted by its developers (Blondin et al, 1987(Blondin et al, , 1989Knobeloch et al, 1990b) and supported more recently by groups of Italian researchers (Argese et al, 1994(Argese et al, , 1995(Argese et al, , 1998Miana et al, 1993;and Bragadin and Dell'Antone, 1994, among others). The focus of these studies has typically been related to an assessment of the comparative sensitivity of an SMP assay with other species and tests.…”

Comparative effects of herbicide dicamba and related compound on plant mitochondrial bioenergetics

“…The mitochondrial fraction is a good model for the study of cell toxicity of xenobiotics in energy metabolism, since data from mitochondrial studies are reasonably correlated with cytotoxicity parameters reported for cell cultures and whole organisms [1][2][3]. These organelles provide the eukaryotic cell of nonphotosynthetic tissue with more than 90% of its total energy requirements.…”