F. B. Daniel

Immunohistochemical analysis of dichloroacetic acid (DCA)-induced hepatocarcinogenesis in male Fischer (F344) rats

We examined the incidence of proliferative lesions, hyperplastic nodules and altered hepatic foci, in male F344 rat liver, to determine their preneoplastic potential during dichloroacetic acid (DCA)-induced hepatocarcinogenesis. Immunohistochemical and image analysis methods were used to detect the expression of 6 histochemical markers of neoplastic cells; p21 ras, p39 c-jun, p55 c-fos, aldehyde dehydrogenase (ALDH), glutathione s-transferase (GST-p), and alpha fetoprotein (AFP) during DCA-induced hepatocarcinogenesis. Our results were consistent with our previous data and suggested that the hyperplastic nodules, rather than altered hepatic foci, is a putative preneoplastic lesion during DCA-induced hepatocarcinogenesis in the male F344 rat.

Effects of four trihalomethanes on DNA strand breaks, renal hyaline droplet formation and serum testosterone in male F-344 rats☆

All four possible trihalomethanes (THMs) containing bromine and chlorine, as well as perchloroethylene (PCE), were evaluated for their ability to produce DNA strand breaks, alpha 2u-globulin rich renal deposits, and testosterone changes in male F-344 rats. Rats received daily equimolar doses (0.75 or 1.5 mmol/kg) of THMs or PCE (1000 mg/kg) in 4% Emulphor vehicle by oral gavage for 7 days. No significant DNA strand breaks were produced by any THM or PCE treatment. PCE treatment produced increased hyaline droplet formation in renal tubules. However, all THM treatments reduced or eliminated the appearance of renal hyaline droplets. All four THM treatments also produced a decrease in serum testosterone concentrations on day 7, which might account for decreased hyaline droplet formation. No significant increase in cell proliferation, measured by [3H]thymidine incorporation in vivo, appeared in this 1-week study.

The Effects of Subchronic Chlorate Exposure in Sprague-Dawley Rats

Male and female Sprague-Dawley rats were exposed to drinking water containing 3.0, 12.0 or 48.0 mM sodium chlorate. The mean drinking water consumption varied between exposure groups from 100-200 ml/kg/day. Female exposure groups consistently drank more water (23-42%) than male exposure groups thereby receiving more chlorate/kg/day at every exposure level. There were no compound related deaths; however, both males and females in the high exposure groups had significant weight loss during the 90-day exposure period. Also, in these same groups females had mild but significant decreases in the following relative organ weights; adrenals, thymus and spleen, while the relative brain weight was increased. In males, the heart, kidneys and liver were mildly decreased while the brain and testes were mildly increased. Red blood cell counts and percent hematocrit were decreased in both sexes in the high dose group. Pituitary gland (pars distalis) vacuolization and thyroid gland colloid depletion were prominent in both sexes in mid and/or high dose animals. A NOAEL of 0.36 mM chlorate/kg b.w./day in males and 0.50 mM chlorate/kg b.w./day in females were established.

Induction of nuclear anomalies in the gastrointestinal tract by polycyclic aromatic hydrocarbons

A selective list of polycyclic aromatic hydrocarbons (PAH) with varied carcinogenic and mutagenic potencies, which are identified as common contaminants at industrial sites and which often contaminate the neighboring ground water, are investigated for their ability to induce nuclear anomalies (NA) in the mouse gastrointestinal (G.I.) tract. These studies examined the hypothesis that a relationship between NA induction and carcinogenic potency of these PAH exists. Among the PAH tested, 7,12-dimethylbenzanthrene (DMBA) was most effective inducer of NA in all G.I. tract tissues examined, with the relative potency in duodenum of DMBA much much greater than benzo[a]pyrene (B[a]P) much greater than benzo[b]fluoranthene (B[b]F). The induction of NA by benzo[a]anthracene (B[a]A), pyrene (PY) and benzo[e]pyrene (B[e]P) was not different from that elicited by vehicle controls. MNU, a known potent inducer of NA in the mouse G.I. tract, yielded a high level of NA in duodenum and proximal colon but was less effective than DMBA in the forestomach. The data suggest that induction of NA by DMBA and B[a]P PAH are in approximate accordance with their relative carcinogenic potency in the gastrointestinal tract. When binary mixtures of some PAH were administered the yield of NA was less than that expected by simple additivity and closer to that expected by averaging the activities of the two PAH comprising the mixture. Thus, this short-term in vivo assay may be useful as a predictor of the genotoxic or carcinogenic strength of individual PAH and/or mixtures of these compounds.

Ten and Ninety-Day Toxicity Studies of chloropicrin in Sprague-Dawley Rats

The toxicity of chloropicrin (CP) was assessed following its administration to rats via oral gavage for either 10 or 90 consecutive days at dose levels of 10, 20, 40, and 80 mg/kg and 2, 8 and 32 mg/kg, respectively. Control rats received corn oil at a dose of 1.0 ml/kg. Toxicological observations included organ and body weight measurements, necropsy and histopathology observations, urinalysis, clinical chemistry and hematology determinations. The most remarkable toxicological finding in both studies was the corrosive property of CP on forestomach tissue. Inflammation, necrosis, acantholysis, hyperkeratosis and epithelial hyperplasia of the forestomach were seen in all dose groups of the 10-day study. Similar changes were detected in only the high dose group in the 90-day study. Decreased red blood cell parameters were noted in the highest dose groups in both studies, possibly due to blood loss via the damaged stomach lining. CP may have been aspirated into the lungs of animals in the high dose group in the ninety day study resulting in pulmonary complications leading to the deaths of 60% of the males and 80% of the females starting at week five. The 8 mg/kg dose group in the ninety day study was considered to be the no observed adverse effect level.

Ten and Ninety-Day Toxicity Studies of 1,2-Dichloroethane in Sprague-Dawley Rats

Male and female Sprague-Dawley rats received 1,2-dichloroethane in corn oil by gavage for 10 or 90 consecutive days. The doses for the 10-day study were 10, 30, 100, and 300 mg/kg; the 90-day study doses were 37.5, 75, and 150 mg/kg. There were ten animals per sex per dose group. In the 10-day study, all female animals died in the high dose group and only 2 of 10 males survived. Final body weights and weight gain along with hematology and clinical chemistry findings were not different from controls. The only relative organ weight which was significantly different was the liver in males exposed to 100 mg/kg. The main histopathological lesion exhibited was multifocal to diffuse inflammation of the mucosal and submucosal layers of the forestomach in the 100 mg/kg dose group. This change was minimal in both males and females. In the 90-day study there were no treatment-related effects pertaining to clinical observations. Body weight gain and total food consumption were significantly decreased in high dose males. There were slight but significant differences in hemoglobin, hematocrit, red blood cell count, platelets, albumin, and alkaline phosphatase values in the 75 and/or 150 mg/kg groups in one or both sexes. In males, relative brain, kidney, and liver weights were significantly increased at 75 and 150 mg/kg. There were also differences in spleen, adrenal, and testes weights (absolute and/or relative). In females, absolute and/or relative kidney and liver weights were significantly increased at 150 mg/kg (liver) and at 75 and 150 mg/kg (kidney). There were no apparent treatment-related effects pertaining to mortality, ophthalmology, gross pathology, or histopathology.

Ninety-day toxicity study of chloral hydrate in the Sprague-Dawley rat.

Male and female Sprague-Dawley rats were administered drinking water containing 300, 600, 1200, or 2400 mg/L chloral hydrate for 90 days. A control group received distilled water only. No animals died during the study and no differences were observed in body weight gain or food and water consumption, except for males at the highest-dose level. Minor treatment-related effects were observed for organ weights and hematological parameters and these did not appear to be of toxicological significance. Some indications of toxicity were evident in the 2400 mg/L male group (equivalent to 168 mg/kg-day) including a significant decrease in food and water consumption and in weight gain. In addition, histopathological examination of these animals revealed an apparent increase in the incidence of focal hepatocellular necrosis. Increases in AST, ALT, and LDH, which occurred at several dose levels in males, but particularly at 200 mg/L, are consistent with the hepatocellular necrosis of minimal to mild severity diagnosed by microscopic examination. These liver changes, except for sporadic enzyme changes, were not seen in the female rats which actually consumed higher doses of chloral hydrate (e.g., 288 mg/kg-day at 2400 mg/L). On the basis of the mild liver toxicity (histopathological and clinical) observed in males at the highest doses (168 mg/kg-day), the no observed adverse effect level (NOAEL) for oral exposure of rats to chloral hydrate for 90 days is considered to be 96 mg/kg-day (600 mg/L).

Toxicity Studies of Epichlorohydrin in Sprague-Dawley Rats

Adult male and female Sprague-Dawley rats received epichlorohydrin via gavage in distilled water for 10 consecutive days at dose levels of 3, 7, 19, and 46 mg/kg-day, and for 90 days at dose levels of 1, 5, and 25 mg/kg-day. Epichlorohydrin did not adversely effect mortality, but toxicity, at the higher doses, was evident by: 1) losses in body weight gain and organ weights, 2) reductions in food and water consumption, and 3) in the hematological and microscopic examinations in both study periods. Significant decreases in erythrocyte count, hemoglobin, and hematocrit levels were found in the high dose level in males after 10 and 90 days. Dose-related increases in kidney and liver weights were observed in both sexes at 25 mg/kg-day in the 90-day study and in various organs for both 19 and 46 mg/kg-day in the 10-day study. Histopathological examination identified the forestomach as the primary target organ for both sexes and in both studies with significant dose-related increases in mucosal hyperplasia (acanthosis) and hyperkeratosis. Based on the data presented, a lowest observable adverse effect level (LOAEL) for oral exposure of Sprague-Dawley rats to epichlorohydrin is 3 mg/kg-day for 10 days and 1 mg/kg-day is suggested as the no observed adverse effect level (NOAEL) for a 90 day oral exposure. These conclusions were the same whether the lesions were analyzed for each sex individually or whether the data in each study was pooled.

Toxicity Studies of 1,3-Dichlorobenzene in Sprague-Dawley Rats

Male and female Sprague-Dawley rats received 1,3-dichlorobenzene daily by corn oil gavage for 10 or 90 consecutive days. The 10-day study doses were 0, 37, 147, 368 and 735 mg/kg; the 90-day study doses were 0, 9, 37, 147 and 588 mg/kg. In the 10-day study, there was a significant depression of body weight in both sexes at 735 mg/kg. Liver weights were significantly increased in both sexes at 368 and 735 mg/kg. Serum cholesterol levels were significantly elevated in both sexes at 368 and 735 mg/kg. Histopathological evaluation revealed centrolobular hepatocellular degeneration at 368 mg/kg in males and 735 mg/kg in females. In the 90-day study, body weights were significantly depressed in both sexes at 588 mg/kg. Normalization of food and water consumption by final body weight indicated that at 588 mg/kg both sexes had increased food and water consumption relative to controls. Absolute and relative liver weights were significantly increased in both sexes at 147 and 588 mg/kg. Relative kidney weights were significantly higher in both sexes at 588 mg/kg and in males at 147 mg/kg. Serum cholesterol and calcium levels were significantly elevated over controls in females at 37, 147, and 588 mg/kg, and in males at all dose levels. Histopathological evaluation at 147 and/or 588 mg/kg demonstrated liver and thyroid lesions in both sexes, and pituitary and kidney lesions in males. A NOAEL was not firmly established.

Toxicity of 1,1,1-trichloro-2-propanone in Sprague-Dawley rats.

1,1,1-Trichloro-2-propanone (1,1,1-TCP) has been identified as a chlorination by-product in finished drinking water supplies. Since little was known of its oral toxicity, exposure studies were conducted with male and female Sprague-Dawley rats (10 males and 10 females/group) exposed by corn oil gavage at 0, 16, 48, 161, or 483 mg/kg for 10 d or 0, 30, 90, or 270 mg/kg for 90 d. Evaluations included mortality, clinical signs, body weight, food consumption, ophthalmology, hematology, clinical chemistry, urinalysis, organ weights, gross pathology, and histopathology. In the 10-d study, severe toxicity was observed at the highest dose level, since most treated animals (8/10 males and 7/10 females) died. Toxicity was also noted at 161 and 48 mg/kg. At 161 mg/kg, 2 males died and an increase in liver weights in both sexes was observed. Acanthosis and hyperkeratosis of the forestomach was present in males and females at 48 mg/kg and above. In the 90-d study, toxicity was significant at 270 mg/kg, with acanthosis and hyperkeratosis of the forestomach evident in most animals and ataxia in about one-half of them. Retinal degeneration, increased serum potassium, and increased blood urea nitrogen were present in females and increased blood calcium in males at that same dose level. Acanthosis and hyperkeratosis were observed in both sexes, and retinal degeneration was prominent in 2 females at 90 mg/kg. It was concluded that 16 mg/kg was the NOAEL (no observed adverse effect level) for the 10-d study while 30 mg/kg was the NOAEL for the 90-d exposure of Sprague-Dawley rats to 1,1,1,-trichloro-2-propanone.