P. Lecavalier

SUBCHRONIC ORAL TOXICITY OF DI-N-OCTYL PHTHALATE AND DI(2-ETHYLHEXYL) PHTHALATE IN THE RAT

The subchronic oral toxicity of di(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DNOP) was studied. Groups of 10 male and 10 female Sprague-Dawley rats were administered DEHP in the diet at 0, 5, 50, 500 or 5000 ppm for 13 wk. In a separate study, groups of 10 male and 10 female Sprague-Dawley rats were given DNOP (5, 50, 500 and 5000 ppm) in the diet while control groups received basal diet containing 4% corn oil and positive control groups were fed a diet containing 5000 ppm DEHP. Growth rate and food consumption were not affected by treatment with either compound. Hepatomegaly was observed in the highest dose groups of both sexes administered DEHP but not in the DNOP-treated animals. At the highest dose, DNOP caused threefold (females) and 12-fold (males) increases in liver ethoxyresorufin-O-deethylase activity while DEHP did not. Mild changes in serum biochemistries were mostly confined to rats in the highest dose group of DEHP, and included increased serum albumin and albumin/globulin ratio in both sexes and decreased cholesterol in female rats. Mild vacuolations in the Sertoli cells were observed in male rats exposed to 500 ppm DEHP. At 5000 ppm DEHP, there was mild to moderate seminiferous tubule atrophy and Sertoli cell vacuolation in males, and rats of both sexes showed hepatic peroxisome proliferation. Both DEHP and DNOP at 5000 ppm caused mild histological changes in the thyroid consisting of reduced follicle size and colloid density, and the liver consisting of endothelial nuclear prominence, nuclear hyperchromicity and anisokaryosis. There was accentuation of zonation of the hepatic lobules and increased perivenous cytoplasmic vacuolation in DNOP-treated rats. Trace quantities (3-5 ppm) of DEHP and DNOP were detected in the liver, and 15-31 ppm were found in adipose tissue of the highest dose groups. The no observed-effect-level was judged to be 50 ppm in the diet or 3.7 mg/kg body weight/day for DEHP, and 500 ppm or 36.8 mg/kg body weight/day for DNOP.

Effects of antimony on rats following 90-day exposure via drinking water

The subchronic toxicity of antimony in drinking water was studied in the rat. Male and female Sprague-Dawley rats (127-135 g body weight, 15 animals per group) were exposed to a soluble trivalent antimony salt, potassium antimony tartrate, in drinking water at concentrations of 0.5, 5, 50 and 500 ppm for 13 wk. Control rats received tap water as drinking water. An additional 10 male and 10 female rats were included in each of the control and 500 ppm groups and were given tap water for a further 4-wk recovery period after the 13-week treatment period. During treatment, the highest dose animals of both sexes consumed significantly less water and showed suppressed body weight gain. During recovery, water intake was quickly restored to that of the control groups and body weight gain was accelerated. At termination, one highest dose male had a cirrhotic liver, and three highest dose males exhibited gross haematuria. Female rats showed a dose-related decrease in serum glucose starting at 5 ppm, and rats of both sexes in the highest dose group had slightly decreased alkaline phosphatase activity and creatinine. The highest dose males had decreased red blood cell and platelet counts and increased mean corpuscular volume. Hepatic glutathione S-transferase activity was increased in the highest dose males and females and ethoxyresorufin-O-deethylase activity was increased in the highest dose males. In the highest dose groups, mild adaptive histological changes were observed in the thyroid, liver and pituitary gland of both sexes, and in the spleen of male rats and thymus of female rats. After a 4-wk recovery period, the pituitary gland of both sexes appeared normal and the changes in the liver and thyroid of both sexes became less severe. On the other hand, minimal changes persisted in the spleen of both sexes and in the thymus of males. Tissue antimony levels were dose-related and follow the order: red blood cells > > spleen, liver > kidney > brain, fat > serum. After the recovery period, antimony level in the highest dose animals decreased for all tissues except the spleen, which remained the same as before recovery. A NOAEL of 0.5 ppm antimony in drinking water, equivalent to an average intake of 0.06 mg/kg body weight/day, was established on the basis of the histological and biochemical changes observed at 5.0 ppm.

Toxicity of 2,2′,4,4′,5,5′-Hexachlorobiphenyl in Rats: Effects Following 90-Day Oral Exposure

The subchronic toxicity of 2,2′,4,4′,5,5′‐hexachlorobiphenyl (PCB 153) was investigated in rats after 13 weeks of dietary exposure. Groups of 10 male and 10 female rats were administered PCB 153 in their diet at levels of 0.05, 0.50, 5.0 or 50 ppm for 13 weeks. The control groups received the diet containing 4% corn oil. Growth rate and dietary consumption were not affected by treatment. Clinical signs of toxicity were not observed. Enlarged, fatty liver was observed in treated animals at necropsy, but most were confined to the two highest dose groups. Increased hepatic microsomal ethoxyresorufin‐O‐deethylase, aminopyrine‐N‐demethylase and aniline hydroxylase activities occurred in high‐dose groups of both sexes, with increased ethoxyresorufin‐O‐deethylase activity being observed starting at 0.05 ppm in females and at 0.5 ppm in males. Treatment‐related reduction in hepatic and pulmonary vitamin A was seen in the highest dose group of both sexes. Changes in brain biogenic amines and intermediate products were observed mainly in females; these included decreased dopamine and 5‐hydroxytryptamine concentrations in the frontal cortex region, and dihydroxyphenylacetic acid in the caudate nucleus region at 5.0 and 50 ppm. Female rats appeared to be more sensitive to the neurotoxic effects of PCB 153 than males. Dose‐dependent histological changes were observed in the thyroid and liver of rats of both sexes and significant changes occurred at 5.0 and 50 ppm. Based on these data, the no‐observable‐adverse‐effect level (NOAEL) of PCB 153 was judged to be 0.5 ppm in the diet or 34 μg kg−1 body wt. day−1.

Subchronic toxicity of PCB 105 (2,3,3′,4,4′-pentachlorobiphenyl) in rats

The toxicity of 2,3,3′,4,4′‐pentachlorobiphenyl (PCB 105) was investigated in Sprague‐Dawley rats following dietary exposure to this substance at levels of 0, 0.05, 0.5, 5 or 50 ppm for 13 weeks. Growth rate and food consumption were not affected and no clinical signs of toxicity were observed. Increased incidences of enlarged, fatty liver and decreased thymic weight were observed in the highest‐dose groups of both genders; these groups also had elevated hepatic microsomal ethoxyresorufin deethylase activity and uroporphyrin. Significant increases in serum cholesterol and hepatic pentoxyresorufin dealkylase activity were observed in the highest‐dose males and two highest‐dose females. By contrast, liver UDP‐glucuronosyl transferase activity was elevated in the two highest‐dose males and the highest‐dose females. Urinary ascorbic acid excretion was increased in the highest‐dose males. While the amount of vitamin A was decreased dose‐dependently, starting at 0.5 ppm in the liver of both sexes and in the lung of the females, the level in the kidney of the highest‐dose group was increased. Administration of PCB 105 resulted in decreased dopamine in the caudate nucleus region of the brain in males and homovanillic acid in caudate nucleus and nucleus accumbens of females. Increased 5‐hydroxytryptamine and 5‐hydroxyindoleacetic acid were observed in the substantia nigra region of both sexes, with most of the increases being seen in highest‐dose females. Anemia, characterized by decreased hemoglobin, hematocrit and red cell indices, occurred in the highest‐dose group, as did eosinophilia. Treatment with PCB 105 caused dose‐dependent histopathological changes in the liver and thyroid. Thymic changes were observed in the highest‐dose males and two highest‐dose females. Tissue residue data showed a dose‐dependent accumulation of this congener in fat, liver and spleen, kidney and brain. Based on these data the no‐observable‐effect level of PCB 105 was judged to be 0.05 ppm or 3.9 μg kg−1 body wt. day−1 in males and 4.2 μg kg−1 body wt. day−1 in females.

Effects of bis(4-chlorophenyl) sulfone on rats following 28-day dietary exposure.

The short-term oral toxicity of a recently identified environmental pollutant, bis(4-chlorophenyl) sulfone (BCPS), was studied. Groups of male Sprague-Dawley rats (n = 6) were administered BCPS via the diet at 0 (control), 10, 100, or 1000 ppm for 4 wk. Additional control and 1000 ppm groups were also treated for 1, 2, and 3 wk. At termination, high-dose animals showed depressed growth rate and food consumption, and 1 high dose animal in each of the wk-1, -3, and -4 groups had marked hematuria. Increased liver to body weight ratio was present at 100 ppm and increased kidney to body weight ratio at 1000 ppm. Marked increases in hepatic benzoylresorufin O-dealkylase (BROD) and pentoxyresorufin O-dealkylase (PROD) activities were detected starting at 10 ppm. There was a significant decrease in methoxyresorufin O-dealkylase (MROD) activity at 1000 ppm. Hepatic UDP-glucuronosyltransferase (UDPGT) and glutathione S-transferase (GST) activities also increased starting at 100 ppm. A marked increase in urinary excretion of ascorbic acid was apparent starting at 10 ppm, while there were no changes in urinary N-acetylglucosaminidase (NAG) activity and protein levels. A threefold increase in serum cholesterol and a 30% increase in platelet counts were observed in the 1000 ppm group. Levels of thiobarbituric acid-reactive substances (TBARS) were increased by threefold in the liver of the high-dose animals but were not significantly altered in the serum. Tissue BCPS concentrations were dose dependent and followed the order: adipose tissue >>> liver > kidneys > brain, spleen, lungs. In the time-course study involving the control and high-dose groups, most of the treatment effects were clearly present in wk 1, and the severity of the effects remained at more or less the same levels thereafter. The exceptions were hepatic BROD and PROD activities, which showed a trend toward further increases with time of treatment. Liver and adipose tissue concentrations of BCPS remained unchanged from wk 1 to wk 4, while kidney concentrations increased with time. The results indicated that BCPS produced hepatic effects at the lowest dose level tested (10 ppm in the diet or 0.8 mg/kg/d).

EFFECTS OF BENZOTHIOPHENE ON MALE RATS FOLLOWING SHORT-TERM ORAL EXPOSURE

The systemic toxicity of benzothiophene, a sulfur-containing heterocyclic present in petroleum, coal, and their derived products, was studied in male rats following short-term oral exposure. Male Sprague-Dawley rats (130 +/- 20 g) (n = 5 per dose group) were treated with benzothiophene by gavage at dosages of 0, 2, 20 or 200 mg/kg/d for 21 d. In another study, male rats were treated with 0, 100, or 500 ppm benzothiophene via the diet for 28 d. In the gavage study, the 200 mg/kg/d rats showed depressed weight gain, increased relative liver and kidney weights, decreased relative thymus weights, and elevated levels of serum gamma-glutamyltransferase (gamma-GT), hepatic aniline hydroxylase (AH), aminopyrine N-demethylase (APDM), pentoxyresorufin O-dealkylase (PROD), glutathione S-transferase (GST), and UDP-glucuronosyltransferase (UDPGT) activities. A 4.5-fold increase in urine volume on d 14-21 and a transient, 4-fold increase in urinary ascorbic acid on d 1 were also detected. No treatment related changes in urinary N-acetylglucosaminidase (NAGA) activity were observed. Benzothiophene residues were not detected in adipose tissue, liver, and serum of rats in the 200 mg/kg rats, but a small quantity was detected in the urine. In the diet study, animals fed the 500 ppm diet had increased absolute and relative liver weights, elevated AH, APDM, and GST activities, decreased red blood cell count, and minor increases in serum urea nitrogen and glucose. In summary, benzothiophene produced adverse effects in male rats that included increased relative liver and kidney weights and increased urine output. Benzothiophene also caused increases in hepatic drug metabolizing enzyme activities of a phenobarbital type and a transient elevation in urinary ascorbic acid.

SUBCHRONIC TOXICITY OF BENZOTHIOPHENE ON RATS FOLLOWING DIETARY EXPOSURE

The systemic and neurobehavioral effects of benzo[b]thiophene (routinely referred to as benzothiophene) were studied in rats following 13-wk oral exposure. Male (170 +/- 16 g) and female (146 +/- 12 g) Sprague-Dawley rats (10 animals per group) were fed diet containing 0.5, 5, 50, or 500 ppm benzothiophene for 13 wk. Control animals were given rat feed plus vehicle (corn oil) only. No clinical signs of toxicity and neurobehavioral effects were observed using screening tests that included cage-side observations, righting reflex, open field activities, and forelimb and hindlimb grip strength. Elevated serum aspartate aminotransferase activity and bilirubin level were observed in highest dose females. Except for a statistically significant decrease in hematocrit in the highest dose males, benzothiophene exerted no marked effects on hematological parameters. Benzothiophene exposure did not result in alterations in hepatic alkaline phosphatase activity, or the typical hepatic phase I (aniline hydroxylase, ethoxyresorufin O-deethylase, pentoxyresorufin O-dealkylase, aminopyrine N-demethylase) and phase II (UDP-glucuronosyltransferase, glutathione S-transferase) drug-metabolizing enzyme activities. No significant elevation in urinary ascorbic acid, protein, and N-acetylglucosaminidase activity was detected in the treated animals. Peribiliary fibrosis was the most significant histological change and occurred in the liver of females in the 50 and 500 ppm groups. Mild epithelial hyperplasia in the renal pelvis was detected in the majority of 5 and 50 ppm females, with epithelial hyperplasia in the urinary bladder observed in the 50 ppm females. In males, increased incidence and severity of mild binucleation of hepatocytes and mild thickening of the basement membrane in kidney cortex were observed at 500 ppm. Benzothiophene was not detected in the urine of high-dose animals at the termination of the experiment. Based on the kidney, hepatic, and hematocrit changes, the no-observed-adverse-effect level (NOAEL) in the diet was determined to be 0.5 ppm (0.04 mg/kg/d) for females and 50 ppm (3.51 mg/kg/d) for males.

Subchronic toxicity of 2,2{prime},3,3{prime},4,4{prime}-hexachlorobiphenyl in rats

The subchronic toxicity of 2,2{prime},3,3{prime},4,4{prime}-hexachlorobiphenyl (PCB 128) was investigated in rats following dietary exposure at 0, 0.05, 0.5, 5, or 50 ppm for 13 wk. The growth rate was not affected by treatment and no apparent clinical signs of toxicity were observed. There was a significant increase in liver weight in the 50 ppm females. The liver ethoxy-resorufin deethylase (EROD) activity was increased by five- and fourfold in the highest dose males and females, respectively, while aminopyrine demethylase (ADPM) activity was significantly increased only in the highest dose females. Liver vitamin A was significantly reduced in the highest dose females. No other biochemical or hematological effects were observed. Treatment-related histopathological changes were seen in the thyroid and liver, and to a lesser extent in the bone marrow and thymus. Residue data showed a dose-dependent accumulation of PCB 128 in the following tissues: fat, liver, kidney, brain, spleen, and serum, with the highest concentration being found in fat followed by liver and kidney. Based on these data, the no-observable-adverse-effect level of PCB 128 was judged to be 0.5 ppm in diet or 42 {mu}g/kg body weight. 29 refs., 1 fig., 5 tabs.