Two-generation reproductive study in mink fed diisopropyl methylphosphonate (DIMP).

Two generations of "Ranch Wild" mink (Mustela vison) were fed the organophosphate diisopropyl methylphosphonate (DIMP) at 0, 150, 450, or 1250ppm, to determine potential toxicity to the dams. Chemical, hematologic, necropsy, and microscopic examinations were performed on all parental animals and representative kits. The F0 and F1 dams had 3.4 and 4.6% mortality, respectively, distributed among all groups and not attributed to DIMP exposure. Adverse effects were mild and limited to the highest dose group. Plasma cholinesterase was reduced 40% (F0) and 31% (F1), as was whole blood cholinesterase (16 and 8.5%). Heinz bodies were present in 2.8% (F0) and 1.3% (F1) of erythrocytes. The erythrocyte count was reduced 6.3% in the F0. Reproductive efficiency was not affected. The mink were not uniquely susceptible to DIMP, relative to the literature on other species. The no observed adverse effect level (NOAEL), based on the 450ppm group of F1 females, was 56.5mg DIMP/kgBW per day; the lowest observed adverse effect level (LOAEL) was 329.5mg DIMP/kgBW per day.

In vivo metabolism of CCl4 by rats pretreated with chlordecone, mirex, or phenobarbital.

The propensity of chlordecone (CD) to potentiate hepatotoxic and lethal effects of CCl4 is well established. Mirex (M), a close structural analogue of CD, or phenobarbital (PB), powerful inducers of hepatic microsomal drug metabolizing enzymes, are much weaker potentiators of CCl4 toxicity. The purpose of this study was to test the possibility that CD potentiates the toxicity of CCl4 by increasing the metabolism of CCl4 to a greater degree than either PB or M. We compared the in vivo metabolism of CCl4 in rats pretreated with CD, M, or PB, by measuring the hepatic content of 14CCl4, the expiration of 14CCl4, expiration of 14CCl4-derived 14CO2, and lipid peroxidation. Male Sprague-Dawley rats (250-270 g) were pretreated with a single oral dose of CD (10 mg/kg), M (10 mg/kg), or corn oil vehicle (1 ml/kg). PB pretreatment consisted of an ip injection of sodium PB (80 mg/kg) in saline (0.9%) for 2 successive days. Twenty-four hours later, 14CCl4 (0.1 ml/kg; sp act: 0.04 mCi/mmol) was administered ip in corn oil and the radioactivity present in the expired air was collected for 6 hr. Excretion of the parent compound as represented by the 14C label in the toluene trap was unchanged by any of the pretreatments. Expiration of 14CO2 measured during the 6 hr after CCl4 administration was increased in animals pretreated with PB or CD. In vivo lipid peroxidation measured as diene conjugation in lipids extracted from the livers was increased to a similar extent in animals pretreated with PB and CD, whereas the serum transaminases (ALT, AST) were significantly elevated only in animals pretreated with CD.M did not affect 14CO2 production and was without a significant effect on the lipid peroxidation. The radiolabel present in the liver at 6 hr showed no difference in hepatic content of free 14CCl4 among the groups, but the covalently bound label present in the lipid fractions of the livers pretreated with PB was elevated in comparison to CD and M treatments. These data indicate that a single oral administration of CD (10 mg/kg) 24 hr prior to CCl4 administration (100 microliter/kg) enhances the oxidative metabolism of CCl4 but to a lesser extent than PB (80 mg/kg, ip, twice), which is in inverse relationship to the potentiation of the hepatotoxic and lethal effects of CCl4 associated with these pretreatments.

Destruction of hepatic mixed-function oxygenase parameters by CCl4 in rats following acute treatment with chlordecone, Mirex, and phenobarbital.

Previous work has established the marked potentiation of CCl4 hepatoxicity by prior exposure to chlordecone (CD). This study was conducted to determine if prior exposure to CD results in enhancement of CCl4-induced destruction of the hepatic microsomal mixed-function oxygenase (MFO) system. Male Sprague-Dawley rats received a single oral dose of CD (10 mg/kg) or corn oil vehicle alone (1 ml/kg) 24 hr prior to a single ip injection of CCl4 (0-100 microliter/kg). Mirex (M; 10 mg/kg) and phenobarbital (PB; 80 mg/kg/day for two days) were used as negative and positive controls respectively for the potentiation of CCl4 hepatotoxicity. Hepatotoxicity was evaluated 24 hrs after CCl4 administration by elevations of three serum enzymes (GPT, GOT, and ICD). The key hepatic microsomal MFO parameters measured were microsomal protein, cytochrome P-450 content, glucose-6-phosphatase (G-6-Pase), and aminopyrine demethylase (APD). As previously demonstrated using a subchronic dietary pretreatment protocol, CD potentiated CCl4 hepatotoxicity over a range of CCl4 doses to a greater extent than PB or M, as judged by elevations in serum enzymes. PB caused the greatest increase in total P-450 content and the greatest increase in CCl4-mediated destruction of microsomal protein and APD activity. M caused the least destruction of total hepatic cytochrome P-450, despite the same level of cytochrome P-450 as in the PB group. CD treatment caused the greatest decrease in G-6-Pase activity in comparison to PB or M pretreatments and a similar degree of P-450 destruction as observed with the PB group. These findings suggest that in general, CCl4-induced destruction of hepatic MFO parameters measured in this study is disproportional to the known degree of potentiated hepatotoxicity by the pretreatments and does not accurately reflect the potentiation of CCl4 hepatotoxicity by CD.

Acute hepatotoxicity and lethality of CCl4 in chlordecone-pretreated rats.

In a subchronic dietary pretreatment protocol chlordecone (CD) is a powerful potentiator of CCl4 hepatotoxicity, as indicated by biochemical, hepatofunctional, histopathological, and lethality parameters. The purpose of this investigation is to further explore the CD + CCl4 interaction in an acute CD pretreatment protocol and to compare the two pretreatment protocols in terms of their effect upon quantitative histopathology, serum enzymes, and lethality. Groups of four male rats received one of the following four pretreatments: chlordecone (10 mg/kg; single po), mirex (10 mg/kg; single po), phenobarbital (PB) (80 mg/kg/day for 2 successive days; ip in 0.9% saline), or corn oil vehicle (1 ml/kg; single po). Twenty-four hours later, the rats were given a single ip injection of CCl4 (0.1 ml/kg). Twenty-four hours after CCl4 administration, serum enzymes (SGPT, SGOT, and ICD) were measured and the livers removed and fixed in 10% buffered formalin for histological evaluation. The LD50 were determined by the method of moving averages. CD + CCl4 was the most hepatotoxic combination, in terms of serum enzyme elevations and lethality followed by PB + CCl4. The PB + CCl4 combination caused a greater degree of hepatocyte necrosis. These findings indicate that the acute pretreatment with CD enhances hepatotoxicity and the lethality of CCl4 in a fashion qualitatively similar to the subchronic pretreatment protocol.

Chlordecone-induced fat depletion in the male rat.

The principal objective of this study was to quantitate the anatomical and biochemical parameters associated with the depletion of body fat by the pesticide, chlordecone (CD, or Kepone). Groups of 5 male Sprague-Dawley rats (150-175 g) were fed a control diet or a diet containing 100 ppm CD for 5, 15, or 20 d. After the treatment period, animals were killed by exsanguination. Weight of the period epididymal fat pads was taken as the anatomical marker for the depletion of body fat. Blood levels of acetoacetate, 3-hydroxybutyrate, and nonesterified fatty acids (NEFA) were measured as biochemical as biochemical markers for lipolysis of body fat depots. Serum enzymes (SGPT, ICD) and serum triglycerides were measured to assess liver damage. A consistent and significant difference was observed in the weight of epididymal fat pads between the control and each of the treatment groups. The reduction in epididymal fat reached a maximum of 60% in the CD-fed animals after 20 d. Circulating ketone bodies were not different in any of the treated-animal groups, indicating that CD treatment does not result in metabolic ketosis. Serum triglycerides and NEFA levels were not significantly different in treatment groups versus in controls. Serum transaminases and isocitrate dehydrogenase were not elevated by exposure to CD. These findings indicate that metabolic ketosis is not induced by dietary exposure to CD. Utilization of lipids as energy substrates appears to be the primary underlying mechanism responsible for the loss of body fat observed in CD-treated rats. It appears that CD induces a depletion of body fat stores as a consequence of altered energy balance of the animal.

Potentiation of CCl4 lethality by chlordecone.

Previous studies have dealt with the propensity of chlordecone (CD) to potentiate the hepatotoxicity of CCl4. The effect of this interaction upon CCl4 lethality has never been reported. The objective of the present study was to evaluate the effect of CD on CCl4 lethality and several parameters associated with cytochrome P-450 activity. Male Sprague-Dawley rats (150-200 g) were fed powdered diets containing 0 to 10 ppm CD or 225 ppm phenobarbital (PB) for 15 days. On day 15, rats from each group received an i.p. injection of CCl4 in corn oil and the 48-h LD50 determined. Additional animals were used to measure hepatic microsomal levels cytochrome P-450 and aminopyrine demethylase. CD decrease the LD50 of CCl4 from 2.8 ml/kg to 0.042 ml/kg, representing a 67-fold increase in toxicity, as assessed by lethality. PB in this protocol decreased the LD50 to 1.7 ml/kg, representing a 1.6-fold increase in lethality. However, the induction of cytochrome P-450 and associated parameters of mixed-function oxidase (MFO) activity did not correlate with the lethality data. Hepatic microsomal P-450 was increased over controls by 40% and 76% in CD and PB rats respectively. PB also stimulated aminopyrine demethylase activity to a much greater extent (190%) than CD (49%) relative to controls. These findings provide evidence that the CD-CCl4 interaction results in a marked increase in CCl4 lethality, in addition to the previously reported marked increase in hepatotoxicity. These results remain consistent with the proposal that bioactivation is the mechanisms underlying enhanced CCl4 toxicity, but suggest that specific effects of CD upon CCl4 metabolism may be the pivotal mechanism underlying potentiation.

Lipid composition of selected tissues of the hardshell clam, Mercenaria mercenaria.

1. The total lipids and lipid classes from six tissues of Mercenaria mercenaria were determined. 2. Polar lipids accounted for the largest fraction of lipids. The highest concentration of polar lipids was found in the gill. 3. Free sterols were found only in trace amounts in the gill but were found in much higher quantities (up to 22.6%) in other tissues. 4. The largest stores of triacylglycerols were in the digestive tract-gonads and adductor muscle.

Distribution of methylene and nonmethylene-interrupted dienoic fatty acids in polar lipids and triacylglycerols of selected tissues of the hardshell clam (Mercenaria mercenaria).

Fatty acid profiles of polar lipids and triacylglycerols were determined for 6 tissues of the hardshell clam (Mercenaria mercenaria), namely, mantle, gill, mouth, foot, digestive tract/gonadal tissue and adductor muscle. The largest concentrations of nonmethylene-interrupted dienoic (NMID) fatty acids were found in the gill, mantle, and foot. Structural analyses were undertaken to determine the double bond configurations of the various NMID isomers. The major 22C NMID species were Δ7,13- and Δ7,15-docosadienoic acid. The major 20C NMID species were Δ7,11- and Δ7,13-eicosadienoic acid and Δ5,11-eicosadienoic acid.