Chronic toxicity of photomirex in the rat

The effect of photomirex on the in vitro perfused ovary of the rat

Photomirex, a photodegradation product of the insecticide mirex, is an environmental contaminant that has been identified in Great Lakes fish, soil, and human adipose tissue. Because of the potential for human exposure, the present study was designed to investigate the short-term effects of photomirex on the in vitro perfused ovary of the rat. Adult Sprague-Dawley rat ovaries were isolated and perfused for a total of 6 h with Medium 199. Following a 2-h baseline period, 10(-4) M of photomirex was administered to the medium. Control ovaries received medium or DMSO (vehicle control). Significant effects of perfusion and chemical intervention were identified using lactate dehydrogenase enzyme, glucose utilization, lactate, pyruvate, and flow:pressure ratio as markers of toxicity (P < 0.05). Lactate:pyruvate ratio, glutathione, and oxygen consumption did not demonstrate significant effects. Post hoc tests showed that there were significant differences between the DMSO + photomirex group and the control group (M199) using lactate dehydrogenase as a marker of toxicity. Pyruvate concentration was also reduced significantly after perfusion with DMSO + photomirex compared to M199 only and DMSO only (P < 0.05). Histopathologic changes were not discernible by light microscopy. These results suggest that metabolic and respiratory processes of the ovary are acutely sensitive to perturbation with photomirex in the in vitro perfused rat ovary model.

ATSDR evaluation of health effects of chemicals. II. Mirex and chlordecone: health effects, toxicokinetics, human exposure, and environmental fate

This document provides public health officials, physicians, toxicologists, and other interested individuals and groups with an overall perspective of the toxicology of mirex and chlordecone. It contains descriptions and evaluations of toxicological studies and epidemiological investigations and provides conclusions, where possible, on the relevance of toxicity and toxicokinetic data to public health. Additional substances will be profiled in a series of manuscripts to follow.

Evidence for and possible mechanisms of non-genotoxic carcinogenesis in rodent liver

Doses of chemicals which induce hepatocellular necrosis usually induce hepatic tumours if the dosing is frequent and is maintained for long periods. Such necrosis is usually evident within 48 h of the first administration. Similarly, chemicals that lead to marked proliferation of peroxisomes in the liver also usually induce hepatic tumours on pretracked regular dosing. For both of these phenomena failure to produce a certain level of effect, or to maintain it for sufficiently long periods, can result in the observation of a non-carcinogenic response. The exact dose/time requirements for carcinogenicity have not been defined and may be species/strain/sex-specific. Some chemicals induce liver enlargement and mitogenesis in the absence of overt hepatotoxic effects. The early phases of hepatomegaly are associated with mitogenic effects that can be measured as cells in S-phase within the first few days of administration. The later stages of hepatomegaly appear to be associated more with cellular hypertrophy. Both effects appear to be threshold-related. Further, sustained hepatomegaly is associated with proliferation of SER and the induction of a range of liver enzymes. These changes (mitogenesis, hepatomegaly, enzyme induction), in isolation, are less definitive indicators of carcinogenicity, but they occur for a sufficient number of liver-specific carcinogens that their role as early indicators is worthy of confirmed study. The major area of study required for all possible early markers of hepatocarcinogenicity is to establish the dose and time dependence of these changes in relation to the eventual appearance of tumours. Finally, the specificity of all these markers require evaluation by the study of appropriate non-carcinogens.

Acute and subacute toxicity of octachlorostyrene in the rat

This study was designed to investigate the acute and subacute toxicity of octachlorostyrene (OCS), a demonstrated environmental pollutant in fish from the Great Lakes and off the Norwegian coast in Europe. In an acute study, groups of 10 male rats were given by gavage single doses of OCS at 1300, 1690, 2190, 2850, or 3710 mg/kg and killed 14 d later. Octachlorostyrene at a dose of 1690 mg/kg and higher caused increased liver weight, increased hepatic microsomal aniline hydroxylase and aminopyrine demethylase activities, and increased serum cholesterol and uric acid levels. Only mild histological changes were seen in the thyroid of the treated animals. In a subacute study, groups of 10 male and female rats were fed diets containing 0.5, 5.0, 50 or 500 ppm OCS for 28 d. Growth rate and food consumption were not affected by treatment. Liver hypertrophy and hepatic microsomal enzyme induction were observed in animals fed 50 ppm OCS or higher. Elevations in serum cholesterol, total protein, potassium, and sorbitol dehydrogenase (SDH) occurred in rats fed the 500 ppm diet. Histological changes occurred in the liver and thyroid of rats exposed to as low as 5.0 ppm OCS. The OCS residues accumulated in the fat and liver in a dose-dependent manner. These data suggest that OCS can produce biochemical and histological changes in rats after administration of a single oral dose and/or when fed in the diet.