Effect of chronic exposure to cadmium on hepatic drug metabolism

Abstract

In an attempt to examine the chronic effect of low levels of cadmium on hepatic drug‐metabolizing enzyme system, an experiment was carried out in which growing male rats were given 0, 5, 10, and 2 0 ppm of cadmium in drinking water for a period of 8 weeks. An ip administration of a hypnotic dose of pentobarbital to the cadmium‐treated and the control rats 2 4 hr following the termination of the experiment exhibited that there was no significant difference in the drug metabolism in control and any of the treated groups. Next, liver microsomes were isolated from animals in all groups to study their ability to metabolize drugs in vitro. The results indicated that the activity of benzphetamine N‐demethylase and aniline hydroxylase, and the concentration of microsomal cytochrome P‐450 were almost identical in the control and treated groups. On the other hand, a single ip dose of cadmium (2 mg/kg) caused significant decrease in the in vivo and in vitro microsomal drug metabolism. These results suggest that although a single ip dose of cadmium (2 mg/kg) causes significant inhibition of drug metabolism, chronic exposure to cadmium up to 2 0 ppm in drinking water over a period of 8 weeks is unlikely to affect hepatic drug metabolism.     

Thiram-induced toxic liver injury in male Sprague-Dawley rats

A single i.p. dose (120 mg/kg) of thiram given to male Sprague-Dawley rats caused a significant increase in the activity of SGOT and SGPT 24 hr post-treatment indicating liver damage. A considerable diminution in the serum cholinesterase activity was also noted in the treated rats as against the control animals. Additional evidence for thiram-induced liver toxicity is provided by the observation that there was approximately 50% inhibition of the activity of hepatic microsomal benzphetamine N-demethylase with a concomitant decrease in the concentration of cytochrome P-450, an important component of the mixed-function oxidase system. Although not significant, hepatic glutathione levels were also depleted by thiram, probably making the liver susceptible to toxic injury.     

Reproduction study of toxaphene in the rat

The purpose of the present study was to investigate in rats the reproductive effects of toxaphene, an insecticidal mixture which has been identified as a pollutant in the Great Lakes ecosystem. Groups of 30 female and 15 male weanling rats were given toxaphene in the diets at 0, 4.0, 20, 100 or 500 ppm in a 1 generation 2 litter reproduction study. Toxaphene treatment at the levels studied had no effects on the litter size, pup weight, fertility, or gestation and survival indices. Toxic effects in the parental rats included depressed weight gain, elevated serum cholesterol, and increased liver and kidney weight and hepatic microsomal enzyme activities. Most of these effects were associated only with 500 ppm toxaphene treatment. Treatment-related histological changes in the liver, thyroid and kidney of adult rats were observed at levels as low as 20 ppm. Based on the data presented, the no observable adverse effect dose of toxaphene was considered to be 4.0 ppm in the diet (0.29-0.38 mg/kg b.w./day depending on the amount of dietary intake).     

Toxicity of pirimiphos-methyl: I. The acute and subacute oral toxicity in albino rats

In an acute study, albino rats of both sexes were orally administered graded doses of Pirimiphosmethyl, and the statistically computed median lethal dose (LD-50) were 1861 and 1667 mg/kg body weight for male and female rats respectively. No treatment related changes were discernible with regard to food intake, growth, gross or histopathology of the organs. In a time-course study, the correlation between symptoms and degree of esterase inhibition was examined in rats administered the minimum lethal dose (MLD: 1000 mg/kg b.w.) of the insecticide. Time-course inhibition pattern of both cholinesterase (ChE) and non-specific carboxylesterase (NSE) activities in brain and plasma revealed maximum inhibition at 24 h post-treatment which correlated well with the intensity of symptoms. In a subacute study, groups of male rats were fed dietary Pirimiphos-methyl at 0, 10, 250, 500 and 1000 ppm for 28 days. Food consumption and growth rate were not affected throughout the experimental period. At necropsy after 28 days, no gross pathological changes were seen in any of the organs except a slight increase in liver weight at 1000 ppm. Though no statistical differences were observed in the levels of hepatic transaminases, a significant increase in serum transaminase was evident. Significant increase in the activities of hepatic ALP, beta-GLR and serum ALP were evident at 500 and 1000 ppm. Further, significant inhibition of plasma PChE was evident at 250, 500 and 1000 ppm while the degree of inhibition of brain AChE was significant only at the higher dosages. No histopathological alterations were observed in any of the organs.     

Biochemical changes produced by beta- and gamma-hexachlorocyclohexane isomers in albino rats

Administration of beta- and gamma-isomers of hexachlorocyclohexane (HCH) at 800 ppm dietary level for 2 weeks to albino rats produced noticeable hepatocellular damage as indicated by elevations in serum aminotransferases and decreases in hepatic soluble enzymes. Although serum total LDH activity was not altered, the LD5 isoenzyme was proportionately higher in the HCH isomers treated animals. Treatment of rats with beta- and gamma-isomers of HCH increased the hepatic glucose-6-phosphate dehydrogenase and aldolase activities suggesting a higher rate of glucose oxidation. Liver glucose-6-phosphatase activity was decreased in these animals indicating inactivation of gluconeogenesis in liver. Dietary beta- and gamma-HCH decreased the liver mitochondrial DNP/Mg++/Ca++-activated ATPases thus affecting the energy metabolism. An unaltered ratio of DNP/Mg++-ATPase, a study of swelling pattern of hepatic mitochondria, and NAD+ permeability test suggested the maintenance of structural integrity of mitochondrial membrane in these pesticide fed animals. Liver microsomal Na+,K+-ATPases were lower in these animals.     

The subchronic toxicity of acridine in the rat

Abstract

The subchronic toxicity of acridine was investigated in rats following dietary exposure at 0, 1, 10, 100 and 500 ppm for 13 weeks. The growth rate and food consumption were not affected by treatment and no clinical signs of toxicity were observed. There was a slight but significant decrease in spleen weight, both in absolute terms and as a percent of body weight, in the 500 ppm males and a slight increase in absolute thymus weight in the females of the same dose group. Both hepatic ethoxyresorufin O‐deethylase (EROD) and pentoxyresorufin O‐dealkylase (PROD) activities were slightly, but significantly, elevated in females in the 500 ppm dose group. No haematological or other biochemical changes were observed. Females also displayed dose‐related increases in inorganic phosphate and uric acid levels. Treatment‐related histopathological changes were seen in the thyroid, liver and kidney and included hepatic anisokaryosis and vesiculation of nuclei and glomerular adhesions, reticulin sclerosis and nuclear pyknosis in the kidney. Residue data showed a dose‐dependent accumulation of acridine in liver, kidney and adipose with the highest concentration being found in the fat of the 500 ppm dose group. Based on these data, the no observable adverse effect level of acridine was judged to be 100 ppm or 12 mg/kg bw/day.     

Thiram‐induced toxic liver injury in male sprague‐dawley rats

Abstract

A single i.p. dose (120 mg/kg) of thiram given to male Sprague‐Dawley rats caused a significant increase in the activity of SGOT and SGPT 24 hr post‐treatment indicating liver damage. A considerable diminution in the serum cholinesterase activity was also noted in the treated rats as against the control animals. Additional evidence for thiram‐induced liver toxicity is provided by the observation that there was approximately 50% inhibition of the activity of hepatic microsomal benzphetamine N‐demethylase with a concomitant decrease in the concentration of cytochrome P‐450, an important component of the mixed‐function oxidase system. Although not significant, hepatic glutathione levels were also depleted by thiram, probably making the liver susceptible to toxic injury.     

Effect of cadmium on ATPase activities in rats fed on iron-deficient and sufficient diets

Male Sprague-Dawley rats were fed on different levels of cadmium mixed with purified diets containing iron or no iron for 8 weeks. The body weight gain, tissue weights, hemoglobin, hematocrit, liver and brain ATPase were measured at 2, 4 and 8 weeks after feeding. The hemoglobin and hematocrit values were the same in all rats fed on cadmium. The rats fed on iron-deficient diets mixed with cadmium showed a significant decrease in body weight gain. However, the rats receiving only the 100 ppm of cadmium in iron-sufficient diet showed a significant decrease in body weight gain. There were no significant changes in the weights of thymus, spleen, kidney, heart, brain and testes. However, the liver weights were decreased in the highest treatment of cadmium but the liver weight/body ratios were uneffected. Na+-K+ activated ATPase activity in brains of rats fed on cadmium were significantly decreased at 2, 4 and 8 weeks of treatment. The decrease was more pronounced in rats fed on iron-deficient diets. Oligomycin-sensitive (Mitochondrial) Mg2+ ATPase activity was also significantly decreased in liver and brain tissues of rats fed on cadmium. Oligomycin-insensitive Mg2+ ATPase activity, however, was not altered in any tissues tested. It appears that cadmium may be interfering with energy (ATP) production and utilization processes in rat brain and liver tissues.     

Toxicological assessment of chlorinated diphenyl ethers in the rat, Part II

Chlorinated diphenyl ethers (CDE's) are environmental contaminants that have been found in Great Lakes fish. Because of the paucity of toxicity data and potential for human exposure, the present short-term study was conducted to assess their potential toxic effects. Groups of 10 male and 10 female rats were administered the three CDE congeners (2,2',4,4',5-pentachlorodiphenyl ether (PCDE), 2,2',4,4',5,5'-hexachlorodiphenyl ether (HCDE), 2,2',3,4,4',6,6'-heptachlorodiphenyl ether (HPCDE] in diets at levels of 0.5, 5.0, 50 or 500 ppm for a period of 4 weeks. Decreased food consumption was observed with male and female rats fed the diet containing 500 ppm HPCDE. Treatment with the three isomers at the highest dose level produced an increase in liver weight in both sexes. While administration of PCDE produced an increase in hepatic aminopyrine demethylase activity, HCDE caused a significant increase in aminopyrine demethylase, aniline hydroxylase and ethoxyresorufin de-ethylase activities. HPCDE caused a significant increase in ethoxyresorufin de-ethylase activity. HPCDE at the highest dose level also caused a significant reduction in circulating lymphocytes in male rats. The 3 CDE's produced mild and adaptative histological changes in the liver and thyroid, but only HPCDE elicited mild changes in the thymus, bone marrow, and spleen. The above data indicate that HPCDE is immunosuppressive and that all three CDE isomers are considered to be moderately toxic in rats. The no-observable effects levels appear to be between 5-50 ppm in diet (0.36-3.0 mg/kg b.w.) for the three CDE's.     

Induction of rat hepatic microsomal enzymes by toxaphene pretreatment

Abstract

The effects of pretreatment of rats with toxaphene on hepatic drug metabolizing enzymes and several other parameters of the mixed function oxidase system were investigated. Adult male Sprague‐Dawley rats were fed diets containing 0, 50, 100, 150 and 200 ppm of toxaphene for 14 days. The body weight gain was unaltered as well as the food consumption in all the toxaphene fed groups. There was no change in the weights of brain, kidney, heart, and testes but the liver weight was significantly increased. The thymus weight in all the toxaphene fed groups was decreased. Hydroxylation of pentobarbital and aniline was significantly enhanced in rats exposed to toxaphene. Ethylmorphine‐N‐demethy‐lase activity in the toxaphene treated rats was also elevated. Enhanced hydroxylation of pentobarbital was also evident from the decreased sleeping time following pentobarbital administration. Exposure to toxaphene increased cytochrome P‐450, NADPH‐cytochrome c‐reductase and dehydrogenase in hepatic microsomal fractions. The binding of aniline and hexobarbital to microsomes was also enhanced, suggesting that the intermediate steps in the electron‐transfer system were increased. In conclusion, pretreatment of rats with toxaphene for fourteen days resulted in the induction of the hepatic mixed function oxidase system.     

Involvement of glutathione in the reduction of captan-induced in vivo inhibition of monooxygenases and liver toxicity in the rat

If given orally captan is relatively nontoxic, but it can be extremely toxic after parenteral exposure. Therefore, a single i.p. dose of captan (20 mg/kg) was given to male Sprague-Dawley rats and its effect on liver microsomal mixed function oxidases and certain serum enzymes (SDH, SGPT and SGOT) was studied. The single dose of captan caused marked depression of microsomal cytochrome P-450 and the activity of benzphetamine N-demethylase and aniline hydroxylase, and moderate elevation of the serum enzymes indicative of liver damage. However, reduced glutathione (100 mg/kg, i.p.) given prior to captan, appears to decrease the liver toxicity as measured by reduced inhibition of the microsomal enzymes and elevation of serum enzymes activity. The results suggest that glutathione and other compounds containing sulfhydryl groups may protect the subjects from captan-induced liver toxicity.     

Pentachlorotoluene and pentabromotoluene: Results of a subacute and a subchronic toxicity study in the rat

Abstract

Pentachlorotoluene (PCT) and pentabromotoiuene (PBT) are environmental contaminants detected in the Great Lakes ecosystem. In view of the paucity of toxicity data and the potential for human exposure, a subacute (28 day) and a subchronic (91 day) study were conducted in the rat. In the subacute study, groups of 10 male and 10 female rats were fed the diet containing PCT or PBT at 0, 0.5, 5.0, 50 or 500 ppm for 28‐days. In the subchronic study, the group size was increased to 15, the dose levels were 0, 0.05, 0.5, 5.0, 50 and 500 ppm in the diet and the exposure period was 91 days. Growth rate and food consumption were not affected by exposure to either chemical in the subacute and subchronic study. Clinical observations revealed no abnormalities. Decreased hemoglobin was observed in female rats fed 5.0 ppm PCT and higher levels in the subacute (28 day) study. In the same study the hematocrit value and erythrocyte numbers of females fed 5.0 or 500 ppm PCT diets were significantly lower than the control. In both subacute and subchronic studies mild dose‐dependent histopathological changes were observed in the thyroid, liver and kidney of rats fed PCT and PBT diets. In general male rats were more susceptible than females to the treatment of PCT and PBT. Based on these data, it was concluded that the no observable adverse effect level for PCT was 50 ppm in the diet (3.5 mg/kg b.w./day) and that of PBT was 5.0 ppm (0.35 mg/kg b.w./day).     

Pentachlorotoluene and pentabromotoluene: results of a subacute and a subchronic toxicity study in the rat

Pentachlorotoluene (PCT) and pentabromotoluene (PBT) are environmental contaminants detected in the Great Lakes ecosystem. In view of the paucity of toxicity data and the potential for human exposure, a subacute (28 day) and a subchronic (91 day) study were conducted in the rat. In the subacute study, groups of 10 male and 10 female rats were fed the diet containing PCT or PBT at 0, 0.5, 5.0, 50 or 500 ppm for 28-days. In the subchronic study, the group size was increased to 15, the dose levels were 0, 0.05, 0.5, 5.0, 50 and 500 ppm in the diet and the exposure period was 91 days. Growth rate and food consumption were not affected by exposure to either chemical in the subacute and subchronic study. Clinical observations revealed no abnormalities. Decreased hemoglobin was observed in female rats fed 5.0 ppm PCT and higher levels in the subacute (28 day) study. In the same study the hematocrit value and erythrocyte numbers of females fed 5.0 or 500 ppm PCT diets were significantly lower than the control. In both subacute and subchronic studies mild dose-dependent histopathological changes were observed in the thyroid, liver and kidney of rats fed PCT and PBT diets. In general male rats were more susceptible than females to the treatment of PCT and PBT. Based on these data, it was concluded that the no observable adverse effect level for PCT was 50 ppm in the diet (3.5 mg/kg b.w./day) and that of PBT was 5.0 ppm (0.35 mg/kg b.w./day).     

Induction of cytochrome P-450 and phosphatidylcholine synthesis by endosulfan in liver of rats: effect of quality of dietary proteins

Administration of endosulfan significantly increased microsomal protein, cytochrome P-450 content and the activity of aminopyrine N-demethylase. Effect of endosulfan and actinomycin D either alone or together on microsomal protein, cytochrome P-450, NADPH cytochrome c reductase, aniline hydroxylase, aminopyrine N-demethylase, phosphatidylcholine content, incorporation of 3H-choline and 14C-methionine were studied in rats given amino acid deficient and supplemented diets. Administration of endosulfan significantly increased the above parameters in both the dietary groups, whereas administration of actinomycin D did not have any effect in rats fed supplemented diets, however, significant decrease in the PC and the incorporation of choline and methionine into PC of rats fed deficient diet were observed. A positive correlation in the effect of endosulfan on hepatic mixed function oxidase activity and hepatic phosphatidylcholine is observed.     

Bioavailability and biological activity of bound residues of radiolabelled pirimiphos-methyl in maize grains.

Using a 14C-labelled pirimiphos-methyl preparation, the percentage of pirimiphos-methyl residues bound to maize grains after 32 weeks of storage was 13% of the applied dosage, or 38% of total terminal residues. Evidence is presented to show that bound residues of pirimiphos-methyl are bioavailable to the rat: 30%, 2% and approx. 6% of radioactivity were measured in urine expired air, and some organs respectively. A major portion of radioactivity (55%) was eliminated through faeces. Grain-bound pirimiphos-methyl residues (generated after storing whole maize grains with pirimiphos-methyl at concentrations of 10 ppm and 100 ppm) were administered to albino rats for 12 weeks. Body and organ weights, enzyme activities and blood chemistry were tested. There was a significant reduction in body weight gain in female rats. Also a significant reduction in blood cholinesterase activity was observed in both male and female rats fed on grain bound pirimiphos-methyl residues at two dose levels. The white blood cell count increased significantly in male rats fed on the high dose. No significant changes were observed in the other blood chemistry parameters tested. The results indicate that maize-bound pirimiphos-methyl residues can exert adverse biological effects in the rat.     

Mixture effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin and polychlorinated biphenyl congeners in rats

Concern of the toxic effects and bioaccumulation of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and polychlorinated biphenyls in the environment continues to be a focus of research in persistent organochlorine contaminants. Groups of five adult female S.D. rats were administered by gavage 0, 2.5, 25, 250 or 1000 ng TCDD/kg body weight/day or TCDD in combination with a mixture of PCB congeners (PCBs) at 2 or 20 microg/kg b.w./day for a period of 28 days. Growth suppression, increased absolute and relative liver weights, and decreased thymic weight were observed in either the 1000 ng TCDD group alone, or the groups receiving a mixture of 1000 ng TCDD + 2 microg PCBs. The TCDD induced increases in liver and thymic weights were not altered by co-administration with PCBs, however, growth suppression appeared to be more pronounced in the group receiving 1000 ng TCDD + 2 microg PCBs than with TCDD alone. Treatment with TCDD at 250 ng and 1000 ng/kg resulted in a significant increase in hepatic microsomal methoxy resorufin-O-demethylase and ethoxy resorufin-O-deethylase activities which were antagonized by co-administration with PCBs. Similarly, effects of 250 ng TCDD on serum cholesterol and liver UDP glucuronosyl transferase activity and ascorbic acid were significantly reduced by co-administration with 20 microg PCBs. Other biochemical effects elicited by treatment with 1000 ng TCDD, but not affected by co-administration with PCBs include the following: increased serum albumin, decreased liver vitamin A, and increased kidney vitamin A and liver microsomal glutathione-S-transferase activity. While decreased hemoglobin, platelet, packed cell volume and red cell indices were observed in TCDD treated rats, no interactive effects were seen. The above results indicate that the mixture effects of PCBs and TCDD may be additive or antagonistic depending on the dose level and endpoints measured. For the purpose of predicting mixture effects, knowledge of mechanisms of action and toxicokinetics is required.     

Toxicity of trichlorotoluene isomers: a 28-day feeding study in the rat

Groups of 10 male and 10 female rats were fed alpha,alpha,alpha-, alpha,2,6- or 2,3,6- trichlorotoluene (TCT) in their diet at 0, 0.5, 5.0, 50 or 500 ppm for 28 days. Growth rate and food consumption were not affected by treatment. No deaths occurred. Significant increases in liver weights were observed in male rats fed 5.0 and 500 ppm 2,3,6-TCT. Mild serum biochemical changes occurred in male rats. These included increased SDH activities in the groups fed 5.0 and 50 ppm alpha, alpha, alpha-TCT, and 5.0 ppm 2,3,6-TCT. Alpha, alpha, alpha-TCT at 500 ppm caused elevated LDH activities in male rats. Hepatic microsomal aminopyrine N-demethylase activities were increased in male rats fed 500 ppm alpha,2,6-TCT. Hematological parameters were not affected by treatment. Mild histological changes were seen in the liver, kidney and thyroid of treated rats. Data presented here suggest that alpha, alpha, alpha-, alpha,2,6- and 2,3,6-TCT possess a low order of oral toxicity in the rat.     

Induction of cytochrome p‐450 and phosphatidylcholine synthesis by endosulfan in liver of rats : Effect of quality of dietary proteins

Abstract

Administration of endosulfan significantly increased microsomal protein, cytochrome P‐450 content and the activity of aminopyrine N‐demethylase. Effect of endosulfan and actinomycin D either alone or together on microsomal protein, cytochrome P‐450, NADPH cytochrome c reductase, aniline hydroxylase, aminopyrine N‐demethylase, phosphatidylcholine content, incorporation of ³H‐choline and ¹⁴C‐methionine were studied in rats given amino acid deficient and supplemented diets. Administration of endosulfan significantly increased the above parameters in both the dietary groups, whereas administration of actinomycin D did not have any effect in rats fed supplemented diets, however, significant decrease in the PC and the incorporation of choline and methionine into PC of rats fed deficient diet were observed. A positive correlation in the effect of endosulfan on hepatic mixed function oxidase activity and hepatic phosphatidylcholine is observed.     

Effect of mixed cadmium,copper, nickel and zinc at different pHs upon alfalfa growth and heavy metal uptake

Alfalfa plants were grown in soil-pots contaminated with a mixture of Cd(II), Cu(II), Ni(II), and Zn(II), (at 50 mg/kg each) at pHs of 4.5, 5.8, and 7.1. The plants were fertilized using a nutrient solution, which was adjusted appropriately to the same pH. Plants in the control treatment were grown in the absence of the heavy metals mixture. The growth of the control plants was the same at the three pHs studied and the heavy metal stressed plants also showed similar behavior at each pHs. There were statistically significant differences (P<0.05) between the shoot length of the control treatment plants and the length of plants grown in the presence of the heavy metal mixture. Under the effects of the heavy metal mixture, nickel was the most accumulated element in the shoot tissue, with 437, 333, and 308 ppm at pH 7.1, 5.8, and 4.5, respectively. Cadmium was found to be second in accumulated concentrations with 202 ppm, 124 ppm, and 132 ppm at pH 7.1, 5.8, and 4.5, respectively, while zinc was third, followed by copper. The maximum relative uptakes (element in plant/element in soil-water-solution) were found to be 26 times for nickel, 23 times for cadmium, 12 times for zinc. and 6 times for copper. We considered these relations as indicative of the ability of alfalfa plants to take up elements from a soil matrix contaminated with a mixture of cadmium, copper, nickel, and zinc.     

Effect of manganese on the concentration of amino acids in different regions of the rat brain

The present study was designed to determine if chronic exposure of weanlings and adult rats to Mn produces significant alterations in amino acid concentrations in different regions of the rat brain. Weanling (30 day old) and adult (90 day old) male rats were exposed to 10 and 20 mg Mn/kg body weight per day, by gavage, for 30 days. Forty-eight hours after the last dose, animals were sacrificed by decapitation and brains were dissected into different regions to determine the concentration of amino acids by HPLC/EC. A dose dependent decrease in body weight gain was found in the adult, but not in the weanling rats. Significant increases occurred in concentrations of aspartate, glutamate, glutamine, taurine and gamma-aminobutyric acid (GABA) in the cerebellum of the adult rats dosed with 20 mg/kg per day, Mn. A significant decrease in the concentration of glutamine was observed in caudate nucleus and hippocampus of weanling rats dosed with 10 mg/kg, Mn. These data suggest that chronic Mn exposure can produce a decrease in body weight gain in adult rats and alterations in amino acids in different regions of weanling and adult rat brains.