SUBMITOCHONDRIAL PARTICLE RESPONSE TO LINEAR ALKYLBENZENE SULFONATES,NONYLPHENOL POLYETHOXYLATES AND THEIR BIODEGRADATION DERIVATIVES

The effects on mitochondrial respiratory parameters of linear alkylben zene sulfonates (LAS), nonylphenol polyethoxylates (NPEO), and some of their biotransformation products, namely sulfophenyl carboxylates (SP Cs), nonylphenol (NP), and nonylphenoxy acetic acid (NP1EC), were reco rded by using the in vitro response of submitochondrial particles (SMP ) from beef heart. The toxicity of these compounds was estimated by de termining their effects on the energy-coupled reverse electron transfe r (RET), which is induced by ATP and succinate at the first site level of the respiratory chain and reduces exogenous NAD+ to NADH. The toxi city of the substances, ''pressed as the toxicant concentration decrea sing the reduction rate of NAD+ to an extent of 50% (EC50), ranged fro m 0.61 mg/L for a commercial LAS mixture to 18,000 mg/L for individual SPCs; from 1.3 mg/L for NPEO, with an average of 10 ethoxy units, to 8.2 and 1.8 mg/L for NP1EC and NP, respectively. These results were re lated to the molecular structure of each compound class and compared w ith the toxicity values obtained by a variety of biological systems cu rrently used for toxicity testing. The acute toxicity data have demons trated that (a) the SMP bioassay is suitable for reproducing the toxic ological response of whole organisms, such as fishes and invertebrates , to the tested chemicals; and (b) the hydrophobic moiety of these com pounds plays a significant role in eliciting their toxic effects. From a toxicological standpoint, attention must be paid to the occurrence in natural waters of residual LAS, whereas in the case of NPEO both un altered surfactant and all biotransformation products need to be ident ified and quantified.