The Acute and Subchronic Toxicity in Rats of Trans-1,2-Dichloroethylene in Drinking Water

Trans-1,2-dichloroethylene was administered either by gavage (acute studies) or in drinking water (subchronic studies) to male and female Sprague-Dawley derived Charles River rats. The acute oral LD50 was 7902 mg/kg for males and 9939 mg/kg for females. Decreased activity, ataxia, and depressed respiration preceded death. In the subchronic study, rats received theoretical daily doses of 500, 1500, and 3000 mg trans-1,2-dichloroethylene/kg body weight/day for 90 consecutive days. The actual daily doses were 402, 1314, and 3114 mg/kg for males and 353, 1257, and 2809 mg/kg for females. There were no compound-related deaths. There were no consistently significant compound-related dose-dependent adverse effects on any of the hematological, serological, or urinary parameters evaluated. There were dose-dependent increases in kidney weights and ratios in treated females. There were no compound-related gross or histological effects. No specific organ site toxicity could be identified in these studies. These data suggest that the toxicity from exposure to trans-1,2-dichloroethylene in drinking water apparently is low and probably does not constitute a serious health hazard.

Oral dietary developmental toxicity study with polyvinyl acetate phthalate (PVAP) in the rat

Polyvinyl acetate phthalate (PVAP) was evaluated in a developmental toxicity study with Crl:CD(SD) rats. Female rats were provided continual access to the formulated diets on days 6 through 20 of presumed gestation (DGs 6 through 20) at concentrations of 0%, 0.75%, 1.5% and 3%. All surviving rats were sacrificed and Caesarean-sectioned on DG 21. The following parameters were evaluated: viability, clinical observations, body weights, feed consumption, necropsy observations, Caesarean-sectioning and litter observations, including gravid uterine weights, fetal body weights and sex, and fetal gross external, soft tissue and skeletal alterations. There were no treatment-related adverse effects reported in the developmental toxicity study. The maternal and developmental no-observable-adverse-effect level (NOAEL) of PVAP was the highest concentration administered, i.e., 3.0% (equivalent to 2324mgPVAP/kg/day).

Twenty eight-day dietary toxicity study of Luo Han fruit concentrate in Hsd:SD rats

A 28-day dietary study was conducted in Hsd:SD rats to evaluate the safety of PureLo, a non-caloric powdered concentrate of the Chinese fruit Luo Han Guo, which derives its sweetening properties from triterpene glycosides called mogrosides. Groups of 20 rats (10/sex/group) were fed diets containing 0, 10,000, 30,000, or 100,000 ppm PureLo for 28 days (OECD, Redbook 2000). PureLo was well tolerated and produced no significant adverse effects. Reduced body weight and body weight gain in high-dose animals of both sexes were related to sporadic reductions in food consumption; there were no overall differences in feed efficiency. Statistically significant changes in clinical chemistry (decreased bilirubin, increased total protein) and relative organ weights of liver, adrenals, ovaries and/or testes, and epididymides were not correlated with any histopathological findings and were not considered adverse. Although a few clinical and pathological findings suggest possible treatment-related effects, particularly in the high-dose group, these findings were transient, not dose-dependent, non-adverse, inconsistent, occurred only in one sex, and/or not supported by histopathological findings. Under the conditions of this study and based on the toxicological endpoints evaluated, the NOAEL for PureLo was 100,000 ppm in the diet, the highest level tested, equivalent to 7.07 and 7.48 g/kg bw/day for male and female rats, respectively.

A critical review of the data related to the safety of quercetin and lack of evidence of in vivo toxicity, including lack of genotoxic/carcinogenic properties

Quercetin is a naturally-occurring flavonol (a member of the flavonoid family of compounds) that has a long history of consumption as part of the normal human diet. Because a number of biological properties of quercetin may be beneficial to human health, interest in the addition of this flavonol to various traditional food products has been increasing. Prior to the use of quercetin in food applications that would increase intake beyond that from naturally-occurring levels of the flavonol in the typical Western diet, its safety needs to be established or confirmed. This review provides a critical examination of the scientific literature associated with the safety of quercetin. Results of numerous genotoxicity and mutagenicity, short- and long-term animal, and human studies are reviewed in the context of quercetin exposure in vivo. To reconcile results of in vitro studies, which consistently demonstrated quercetin-related mutagenicity to the absence of carcinogenicity in vivo, the mechanisms that lead to the apparent in vitro mutagenicity, and those that ensure absence of quercetin toxicity in vivo are discussed. The weight of the available evidence supports the safety of quercetin for addition to food.

A 13-week dietary toxicity and toxicokinetic study with l-theanine in rats

This study was conducted to evaluate the safety of l-theanine (Suntheanine) when administered as a dietary admixture to male and female Crl:CD (SD)GS BR rats at concentrations providing doses of 0, 1500, 3000 or 4000 mg/kg bw/day for 13 weeks. The study design was consistent with OECD Guideline 408 and USFDA Redbook II (1993) and GLP. There were no consistent, statistically significant treatment-related adverse effects on behavior, morbidity, mortality, body weight, food consumption and efficiency, clinical chemistry, hematology, or urinalysis. There were no consistent treatment-related adverse effects in gross pathology, organ weights or ratios or histopathology. The increased incidence of renal tubular cell adenomas in high-dose females only were not consistent with the characteristics of a renal carcinogen (due to early onset and low number of animals affected) but were more consistent with a genetic predisposition than with direct organ toxicity. The no-observed-adverse-effect-level (NOAEL) was 4000 mg/kg bw/day, the highest dose tested.

A subchronic toxicity study in rats and genotoxicity tests with an aqueous ethylcellulose dispersion

Surelease Aqueous Ethylcellulose Dispersion is an excipient used as a modified release coating for beads, granules, non-pariels, drug crystals and tablets and for taste masking applications for drug products and dietary supplement products. A study was conducted to assess the toxicity of spray-dried Surelease when administered orally, via dietary admixture, to Sprague-Dawley CD rats (20/sex/group) at dose levels of 0, 2000, 3500, and 5000 mg/kg/day for a period of at least 3 months. After 3 months of treatment, all rats scheduled for terminal sacrifice were killed and selected organs were weighed. Complete macroscopic examinations and histopathological evaluation of selected tissues were conducted on all animals. Neuropathological evaluations were performed on 5 animals/sex/group. No mortality occurred during the study. Clinical observations, ophthalmology, body weight and food consumption, hematology, coagulation, clinical chemistry, urinalysis, functional observational assessments, motor activity, organ weights and ratios and macroscopic and microscopic observations did not reveal any significant, consistent, dose-dependent test article-related adverse effects. The NOAEL (no-observed-adverse-effect-level) is 5000 mg/kg/day, the highest dose tested. A series of genotoxicity tests were conducted with Surelease. Surelease showed no evidence of mutagenic activity in the bacterial reverse mutation test with and without metabolic activation and in the in vitro cell mutation assay under the experimental conditions employed. Surelease did not show any evidence of causing chromosome damage or bone marrow cell toxicity when administered by gavage in the mouse micronucleus in vivo test procedure. These findings support the safety of Surelease for use as an excipient.

Glucosamine effects in humans: a review of effects on glucose metabolism, side effects, safety considerations and efficacy

Glucosamine is widely used to relieve symptoms from osteoarthritis. Its safety and effects on glucose metabolism are critically evaluated in this review. The LD50 of oral glucosamine in animals is approximately 8000 mg/kg with no adverse effects at 2700 mg/kg for 12 months. Because altered glucose metabolism can be associated with parenteral administration of large doses of glucosamine in animals and with high concentrations in in vitro studies, we critically evaluated the clinical importance of these effects. Oral administration of large doses of glucosamine in animals has no documented effects on glucose metabolism. In vitro studies demonstrating effects of glucosamine on glucose metabolism have used concentrations that are 100-200 times higher than tissue levels expected with oral glucosamine administration in humans. We reviewed clinical trial data for 3063 human subjects. Fasting plasma glucose values decreased slightly for subjects after oral glucosamine for approximately 66 weeks. There were no adverse effects of oral glucosamine administration on blood, urine or fecal parameters. Side effects were significantly less common with glucosamine than placebo or non-steroidal anti-inflammatory drugs (NSAID). In contrast to NSAID, no serious or fatal side effects have been reported for glucosamine. Our critical evaluation indicates that glucosamine is safe under current conditions of use and does not affect glucose metabolism.

Effects of polyvinyl alcohol administered in the diet to rats on fertility, early embryonic development, growth and development

PVA was administered in the diet to male and female Sprague-Dawley rats (26/sex/group) at doses of 0, 2000, 3500 and 5000 mg/kg/day for two generations. The study design assessed gonadal function, estrous cycle, mating behavior, conception, gestation, parturition, lactation, weaning, and growth and development of F(1) and F(2) offspring. Parental rats were treated for 70 days prior to mating, throughout mating, gestation and lactation until sacrifice. Clinical observations, body weights and feed consumption were recorded routinely. Dietary concentrations were adjusted for each sex on a weekly basis except during gestation and lactation, to provide the intended mg/kg/day PVA levels. Pups were weighed routinely and weaned at 21 days of age prior to selection for the next generation. Unformed stool was noted predominately at the 3500 and 5000 mg/kg/day levels in P(0) and F(1) parental animals. This finding was attributed to the high levels of PVA being fed and subsequently excreted in the stool. Slight decreases in the mean body weights of P(0) males were noted at 2000 and 5000 mg/kg/day. Feed consumption was elevated at the 3500 and 5000 mg/kg/day doses in both generations but not during either lactation period. These increases generally were observed in a dose-related manner (g/kg/day), as a result of the large amount of PVA being consumed to maintain the caloric intake necessary for normal growth. There were no effects of PVA on P(0), F(1) male or female reproductive performance or pup survival, growth, organ weights, and macroscopic or microscopic observations at doses of 2000, 3500 and 5000 mg/kg/day. Therefore the no-observed-effect level (NOAEL) is 5000 mg/kg/day for both parental and offspring in this reproductive study.

Subchronic toxicity study in rats and genotoxicity tests with polyvinyl alcohol

The potential systemic and neurotoxicity of polyvinyl alcohol (PVA) was assessed when fed in the diet to male and female Sprague-Dawley rats for 90 days at doses of 2000, 3500 and 5000 mg/kg/day. Control rats received untreated standard laboratory diet. Assessments included clinical observations, ophthalmology, body weight and food consumption, hematology, coagulation, clinical chemistry, urinalyses, motor activity and functional observational battery evaluations and gross and microscopic pathology. The only test-article-related finding observed during the study was unformed stool with brown/black anogenital staining in rats fed 3500 and 5000 mg/kg/day. This finding was attributed to the high levels of test article being consumed and subsequently excreted in the stool. It was not accompanied by macroscopic or microscopic changes in these rats. No test-article-related changes were seen in mortality, ophthalmology, body weight and food consumption data, hematology, clinical chemistry, urinalysis data, functional observational assessments, motor activity, organ weight data and macroscopic and microscopic examinations. Doses of 2000, 3500 and 5000 mg/kg/day of PVA administered as a dietary admixture to male and female Sprague-Dawley rats for up to 90 days did not result in any adverse, toxicological effects. The no-observed-adverse-effect level (NOAEL) was determined to be 5000 mg/kg/day. PVA showed no evidence of mutagenic activity in the Ames test, mouse lymphoma assay and the mouse micronucleus test. (A critical evaluation of the available information on PVA will appear in a review to be published in Food and Chemical Toxicology 2003, 41, 319-326)

Evaluation of the toxicity of polyvinylacetate phthalate in experimental animals

Polyvinylacetate phthalate (PVAP) is used in the pharmaceutical industry as an ingredient in coating systems for oral solid dosage forms and in inks for monogramming capsules. PVAP has been evaluated in both sexes of several species in a number of toxicological studies including acute, repeated dosing, subchronic, chronic and reproductive and developmental. The acute oral toxicity is low in rats and mice (LD(50) > 8000 mg/kg body weight), although it appears to be more toxic in the dog. The gastrointestinal tract appears to be the target organ and effects seen (irritation, laxation, colitis with erosions and submucosal fibrosis in the dog and ulcers, polyps, and cecal wall thickening in rats) were dose dependent. There were no consistent treatment-related adverse effects on reproductive performance or development (not teratogenic). The no-observed-adverse-effect levels (NOAELs) ranged from 100 mg/kg body weight/day in the rabbit developmental toxicity study, to 500 mg/kg body weight/day in 24 month rat and dog studies, to 1000 mg/kg body weight/day in a one-generation reproduction study in the rat.

Comparison of AIN-76A and AIN-93G diets: a 13-week study in rats

Either purified or cereal-based diets may be used for toxicity testing in rats. Purified diets have advantages in terms of flexibility of formulation to meet specific study objectives and also assurance of relatively low levels of contaminants (e.g. heavy metals and pesticides). The American Institute of Nutrition recommended that the widely used purified diet AIN-76A be replaced by two newer diets, AIN-93G (for use during rapid growth, pregnancy and lactation) and AIN-93M (maintenance diet). The present study compared AIN-76A and AIN-93G by feeding these diets for 13 weeks to male and female rats. A cereal-based diet was also included for reference purposes. The groups fed purified diets had higher serum cholesterol and triglyceride levels than the chow-fed group. An increased incidence and severity of renal tubular mineralization in the purified diet groups was not observed in this study (in contrast to other published studies where rats were fed AIN-76A). Several histopathologic observations, including eosinophilic gastritis and mucification of gastric glands of the glandular stomach, occurred at higher rates in the AIN-76A group than the other dietary treatments. Hepatocellular fatty changes occurred in the purified diet groups at a significantly higher rate than in the chow diet group. In conclusion, AIN-93G is an appropriate diet for use in rat safety evaluation studies.

Safety evaluation of ferrous bisglycinate chelate

Ferrous bisglycinate chelate (Ferrochel) is a highly stable chelate that can be added to most foods. Data from human and animal studies indicate that the ferrous iron is readily bioavailable with fewer side-effects than the more commonly used iron salts. The acute oral LD50 for male and female Sprague-Dawley (S-D) rats is 2800 mg/kg body weight (560 mg/kg body weight iron [confidence limit (CL) 399-786] as the active ingredient). Male and female CD (Sprague Dawley-derived) rats were fed ferrous bisglycinate as a dietary admixture at doses of 0, 100, 250 and 500 mg/kg body weight/day. There were no biologically or statistically significant dose-related differences between the control and treated animals with respect to body weight gain, food consumption, food efficiency, behavioural effects, clinical chemistries, haematology, absolute and relative organ weights, or gross and microscopic findings. Hepatic non-heme iron concentrations were elevated, indicating that the ferrous iron had been absorbed. The no-observed-adverse-effect level (NOAEL) was 500 mg/kg body weight/day, the highest dose tested.

Erythritol: an interpretive summary of biochemical, metabolic, toxicological and clinical data

A critical and comprehensive review of the safety information on erythritol was undertaken. Numerous toxicity and metabolic studies have been conducted on erythritol in rats, mice and dogs. The toxicity studies consist of long-term feeding studies conducted to determine carcinogenic potential, intravenous and oral teratogenicity studies to determine the potential for effects on the foetus, oral studies in which erythritol was administered over one or two generations to determine the potential for reproductive effects, and studies in bacterial and mammalian systems to determine mutagenic potential. The majority of the safety studies conducted were feeding studies in which erythritol was mixed into the diet at concentrations as high as 20%. The metabolic studies in animals have shown that erythritol is almost completely absorbed, not metabolized systemically and is excreted unchanged in the urine. The safety studies have demonstrated that erythritol is well tolerated and elicits no toxicological effects. The clinical program for erythritol involved a series of single-dose and repeat-dose, short-duration studies which have been used to investigate the human correlates to the physiological responses seen in the preclinical studies. The clinical studies showed erythritol to be well tolerated and not to cause any toxicologically relevant effects, even following high-dose exposure. Erythritol administered orally to humans was rapidly absorbed from the gastrointestinal tract and quantitatively excreted in the urine without undergoing metabolic change. At high oral doses, urinary excretion accounted for approximately 90% of the administered dose with minimal amounts appearing in the faeces. A comparison of the human and animal data indicated a high degree of similarity in the metabolism of erythritol and this finding supports the use of the animal species used to evaluate the safety of erythritol for human consumption. It can be concluded, based on the available studies that erythritol did not produce evidence of toxicity.

Assessment of cassia gum

Cassia gum is approved for use in Europe by the Commission Directive (EEC No. E 499) and is listed in the Annex of the Council Directive (70/524/EEC) as a stabilizer (thickening and gelling agent) in the manufacture of canned pet foods (for cats and dogs). It is also approved for use in Japan and is listed as a food additive in The Ministry of Health and Welfare Announcement No. 160 (10 August 1995). A panel of experts in the areas of toxicology, pharmacology and food science was assembled to review the safety of cassia gum for use as a thickening agent in human and pet foods in the United States. The available data on cassia gum and structurally related gums demonstrate a lack of toxic effects in animals. This review is the basis for the consideration of cassia gum as generally recognized as safe (GRAS) under conditions of its intended use as a thickening agent in human and pet foods.

A new approach to the safety assessment of pharmaceutical excipients. The Safety Committee of the International Pharmaceutical Excipients Council

This article presents a set of proposed guidelines for the safety assessment of new pharmaceutical excipients. These guidelines were developed by the Safety Committee of the International Pharmaceutical Excipients Council and represent a new, scientifically based approach to establishing conditions for the safe use of proposed pharmaceutical excipients utilizing various routes of human exposure. They are based upon the best currently available toxicological science and have taken the deliberations of the International Conference on Harmonization into consideration. These guidelines were developed because there are no regulatory agency guidelines currently available which specifically address the toxicological testing of a material intended for use as an excipient in pharmaceutical preparations. Only materials which have been previously permitted for use in a pharmaceutical preparation or which have been permitted for use in foods may be considered safe under current practices. If implemented, these guidelines should expedite the review of a proposed new excipient by regulatory agencies.

Serum creatine kinase does not predict ectopic pregnancy

OBJECTIVE

To evaluate the discriminatory ability of maternal serum creatine kinase (SCK) as a test for ectopic pregnancy (EP).

DESIGN

Serum creatine kinase concentrations were obtained prospectively from symptomatic patients being evaluated for early abnormal pregnancy. Serum creatine kinase concentrations from all patients and from a subset of these patients with maternal serum beta-hCG concentrations < 6,500 mIU/mL (conversion factor to SI unit, 1.00) were analyzed with descriptive statistics, receiver operator characteristic (ROC) curve analysis, and calculations of predictive values.

SETTING

A university hospital emergency room.

PATIENTS

Fifty-six patients with intrauterine gestations (25 with beta-hCG concentrations < 6,500 mIU/mL) and 23 patients with EP (20 with beta-hCG concentrations < 6,500 mIU/mL) were studied.

RESULTS

For all patients and the subgroup with beta-hCG concentrations < 6,500 mIU/mL, mean SCK levels were not significantly different between ectopic and intrauterine gestations. For all patients and the subgroup with beta-hCG concentrations < 6,500 mIU/mL, the areas under the ROC curves did not demonstrate discriminatory ability of the SCK test. The highest positive predictive value of an elevated SCK for EP was 52% using the SCK concentration of 70 U/L, and this was seen in the subgroup of patients with beta-hCG values < 6,500 mIU/mL.

CONCLUSIONS

Maternal SCK concentrations do not reliably predict EP.

A proposed model for safety assessment of macronutrient substitutes

Restriction of fatty foods is an effective means of reducing caloric intake and is consistent with public health goals to reduce the risk of chronic diseases. Compliance with low-fat diets is enhanced by the substitution of foods with the same organoleptic properties as fat, namely flavor, texture, and mouth-feel. Fat substitutes could replace a significant proportion of dietary fat and as such become macronutrient substitutes. The safety of these materials must be established prior to introduction into the food supply. As their use increases so will concerns about their safety. Appropriate methods of safety evaluation must be used. Traditional methods for the safety evaluation of food additives are inappropriate, since concentrations of the test materials high enough to provide a 100-fold safety factor cannot be used. An approach that recognizes the unique nature of macronutrient substitutes and includes the use of in vitro, whole-animal, and human studies and nutritional, physiological, and toxicological end points is proposed. Evaluations in humans are conducted early in this program but only when the animal data adequately support these studies. Human data will complement the animal data and may eliminate the need for some animal studies. The introduction of postmarketing surveillance will identify consumption patterns, associated adverse reactions, and potentially sensitive segments of the population and will ensure the continued safety of macronutrient substitutes.

Evaluation of the safety of sodium pectate as a food ingredient

New potential uses of pectates in food products have recently stimulated interest in re-evaluating the information available concerning the safety of pectins and pectates as food ingredients. Data relevant to this re-evaluation have been obtained in rats in recent 14-day and 13 wk subchronic feeding studies with sodium pectate. Ames tests and other mutagenicity tests have been conducted with sodium pectate, bleached sodium pectate and mixed sodium/calcium pectate salts. These toxicological studies with pectates have provided further evidence of their safety, and support of the continued GRAS status of pectins and pectate salts.

Toxicological evaluation of mu-agonists. Part II: Assessment of toxicity following 30 days of repeated oral dosing of male and female rats with levo-alpha-noracetylmethadol HCl (NorLAAM)

This study evaluated levo-alpha-noracetylmethadol (NorLAAM), the first N-demethylated metabolite of levo-alpha-acetylmethadol (LAAM), a long-acting morphine-like (mu) agonist, approved in 1993 to treat opiate dependence. After acute and 7-day pilot studies to define dose levels appropriate for use in longer term evaluations, Sprague-Dawley rats (20 of each sex per group) were gavaged with doses of 4.4-25.9 mg kg(-1) day(-1) for 30 days followed by a 14-day recovery period. Treatment-related effects included dose-dependent CNS depression paralleled by changes in food consumption, body weight gain and fecal output, as well as reddish urine and abdominal staining. Tolerance developed by day 7. The spectrum of activity observed differed from the parent compound primarily in its time course. Cage-biting and gnawing behavior were observed only with NorLAAM. Mortality was dose-dependent, with deaths occurring predominantly during the first week. At day 30, all male-treated groups exhibited statistically significant, dose-dependent decreases in body weight gain and increases in serum cholesterol that returned to the control range following recovery. Increases in brain/body weight and testes/body weight ratios and decreases in kidney/brain, liver/brain, spleen/brain and heart/brain ratios, as well as decreases in kidney, liver, spleen and heart absolute weights, achieved statistical significance only for males. At terminal sacrifice, histological findings in the kidneys included increased incidences of tubular mineral deposition in mid- and high-dose groups of both sexes and of corticomedullary mineral deposition in females. Hepatic centrilobular hypertrophy was evident in male and female mid- and high-dose groups. Histopathological changes abated following the recovery period. In summary, acute and repeated administration of NorLAAM produced a pharmacodynamic profile commensurate with its role as the primary N-demethylated metabolite of LAAM, which is more potent and less lipophilic than the parent compound; this was reflected in the toxicological outcomes observed. Like LAAM, NorLAAM's overall pattern of activity is consistent with its activity as a mu-agonist, which stimulates hepatic microsomal enzymes in rodents.

alpha-Benzyl-N-methylphenethylamine (BNMPA), an impurity of illicit methamphetamine synthesis: pharmacological evaluation and interaction with methamphetamine

Methamphetamine is a popular drug of abuse, readily synthesized in clandestine laboratories. Illicitly obtained methamphetamine is frequently impure, containing various purposefully added diluents and adulterants, as well as impurities of manufacture and origin. Few impurities have been studied in vivo and limited information exists concerning their pharmacology/toxicology. One such impurity of manufacture is alpha-benzyl-N-methylphenethylamine (BNMPA). Acute toxicity and spontaneous activity (locomotor) studies were conducted with this compound alone and in combination with S(+)-methamphetamine (METH) in male, ICR mice. In the acute toxicity studies, BNMPA was evaluated for convulsant activity. While BNMPA also produced some behavioral disturbances similar to those seen with methamphetamine (e.g., stereotopy) at doses greater than 30 mg/kg, no tonic-clonic convulsions were noted until pre-terminal convulsion at 50 mg/kg. METH alone produced tonic-clonic convulsions at terminal doses of 70 mg/kg. When BNMPA was given in combination with METH, there was no readily apparent change in the convulsion profile from that of METH given alone. In spontaneous activity studies, doses of BNMPA ranging from 1 mg/kg to 50mg/kg failed to alter locomotor activity significantly from controls though 5 mg/kg METH alone significantly increased spontaneous activity. In addition, increases in spontaneous activity elicited by 5 mg/kg METH were not affected when METH was given with 5 mg/kg BNMPA. While BNMPA appears to have toxic effects in the central nervous system (CNS), the failure to affect locomotor activity or alter either METH-induced increases in spontaneous activity or METH-induced convulsions suggests that the two agents are producing their effects through distinct mechanisms.

The safety and regulatory status of food, drug and cosmetics colour additives exempt from certification

Colour additives exempt from certification (also known as 'natural colour additives') are commonly used in the United States to colour foods, drugs and cosmetics. The US Food and Drug Administration established regulations governing the use of these colour additives, and the labelling of the products that contain them. The safety of these colour additives has been demonstrated by safety testing programs that have yielded a significant amount of toxicology data, and also by a long and well documented history of safe use in the United States and elsewhere. In this report we review the data supporting the safety of the colour additives that are exempt from certification and approved for use in the USA, and conclude that the safety of these colour additives is well supported by the available data. Relevant aspects of the regulation of these colour additives are also described.

Safety assessment of polylactide (PLA) for use as a food-contact polymer

This report constitutes a safety assessment of polylactide (PLA), a polymer of lactic acid intended for use in fabricating various food-contact articles. Migration studies were conducted on samples of the polymer following guidelines issued by the Food and Drug Administration. Potential migrants from PLA include lactic acid, lactide (the monomer), and lactoyllactic acid (the linear dimer of lactic acid). The studies were designed to model reasonable 'worst' case extraction situations when the polymer is used (a) in houseware articles for short and intermediate time periods at various temperatures and (b) in food-packaging materials. The limited migration observed during the trials represents no significant risk since migrating species are expected to convert to lactic acid, a safe food substance. It is concluded that PLA is safe and 'Generally Recognized As Safe' for its intended uses as a polymer for fabricating articles that will hold and/or package food.

Toxicological evaluation of mu-agonists. Part I: Assessment of toxicity following 30 days of repeated oral dosing of male and female rats with levo-alpha-acetylmethadol HCl (LAAM)

This study evaluated levo-alpha-acetylmethadol hydrochloride (LAAM), a long-acting morphine-like (mu) agonist approved in 1993 to treat opiate dependence. Sprague-Dawley rate (20/sex/group) were gavaged with doses of 3.0-33.5 mg kg-1 for 30 days followed by a 14-day drug-free recovery period. Treatment-related effects included dose-dependent CNS depression, decreased food consumption and body weight gain, reddish urine and abdominal staining. Tolerance developed by day 7. Mortality was dose-dependent; deaths occurred predominantly during the first week. Increased alanine aminotransferase (SGOT, AST) and lactate dehydrogenase (LDH), observed only in high-dose males, were associated with findings in liver. Decreases in spleen/brain weight and increases in brain/body weight ratios were seen in both sexes. Decreases in weights of heart, liver and kidney achieved statistical significance only for high-dose groups. Kidneys of mid- and high-dose groups displayed intertubular mineral/crystal deposition, focal corticomedullary mineralization and focal regenerative tubular epithelium. Centrilobular hypertrophy was observed in livers of high-dose males and mid- and high-dose females. Following the recovery period, decreased body weights and increased brain/body weight ratios occurred in mid-dose males and low-dose females. Weights of liver and kidney and organ/brain weight ratios were decreased in mid-dose males. Histopathological findings observed in kidneys and livers had abated. In summary, acute and repeated administration of LAAM produced a spectrum of activity consistent with its profile as a long-acting pure mu-agonist which stimulates microsomal enzymes in rodents. Renal and hepatic effects seen in initially drug-naive rats treated with morphine-type agonists are not observed in tolerant individuals stabilized on mu-agonists to treat opiate dependence.

Macronutrient substitutes: safety evaluation

Macronutrient substitutes, reduced-calorie substances used to replace organoleptic and/or functional properties of fats and sugars in the diet, may become a significant part of the diet as the trend toward lower fat and lower calorie diets continues. Procedures currently used to evaluate the safety of traditional food additives (microadditives) may be inadequate to properly assess the safety of macronutrient substitutes (macroadditives) because of the unique nature of these substances and the potentially large intakes. An evaluation procedure is proposed that recognizes the benefits to be derived from the test material, uses a structured approach to obtain animal and human nutritional and toxicological (including kinetic and dispositional) data that are critically evaluated and that provide a basis for further testing, encourages consultation with the regulatory agency (FDA), and recommends postmarketing surveillance of the macronutrient substitute. The proposed scheme differs from the traditional approach in many respects, such as using dispositional and kinetic data, assessing nutritional status, using human data collected under carefully controlled conditions early in the process, and consulting with the FDA. A case-by-case approach is recommended for safety evaluation of these macroadditives.

Lifetime toxicity/carcinogenicity studies of FD & C red no. 40 (allura red) in mice

FD & C Red No. 40 (allura red) was fed to Charles River HaM/ICR (CD-1) (study A) and CD-1 outbred (study B) mice as a dietary admixture in two separate lifetime toxicity/carcinogenicity studies. Each study included an in utero exposure phase during which the colouring was fed at dietary concentrations of 0.0, 0.37, 1.39 or 5.19% throughout the mating, gestation and lactation periods. After random selection, the lifetime exposure phase was initiated using the same dietary concentrations with 50 mice/sex/group in study A and 100 mice/sex/group in study B. Exposure was for 104 wk in study A and 109 wk in study B. No compound-related adverse effects were observed. The no-observable-adverse-effect level in these studies was 5.19%; approximately 7300 and 8300 mg/kg body weight/day for male and female mice, respectively.

A CCl4/CHCl3 interaction study in isolated hepatocytes: non-induced and phenobarbital-pretreated cells

The purpose of this study was to evaluate an isolated hepatocyte model for predicting the in vivo hepatotoxicity of carbon tetrachloride (CCl4) and chloroform (CHCl3), alone and in combination. Response surface methodology (RSM) was used to analyze and describe the data. The interaction was evaluated for % initial K+ (cell injury) and % LDH leakage (cell death) in non-induced (untreated) and phenobarbital-pretreated suspended hepatocytes. CCl4 and CHCl3 were delivered alone and in combination in dimethyl sulfoxide (DMSO) to suspended hepatocytes. The maximum observed no-effect level (MONEL) for CCl4 in non-induced cells was 1.0 mM (LDH and K+). In induced cells, the MONEL was 0.25 mM (K+) and 0.5 mM (LDH). The MONEL for CHCl3 in non-induced cells was 5.0 mM (LDH and K+) and in induced cells was 0.5 mM (K+) and 1.0 mM (LDH). Phenobarbital pretreatment enhanced the toxicity of both CCl4 and CHCl3, alone and in combination. RSM analysis of the % initial K+ and % LDH for CCl4 and CHCl3 in combination in noninduced and induced cells showed a greater than additive interaction. The isolated hepatocyte model appears to be a promising system for evaluating the toxicity of chemical mixtures and predicting their in vivo effects.

Multigeneration study of FD & C Red No. 3 (erythrosine) in Sprague-Dawley rats

Sprague-Dawley rats received dietary admixtures containing 0.0, 0.25, 1.0 or 4.0% FD & C Red No. 3 (25 rats/sex/group) in a three-generation reproduction study. Each generation was bred twice and breeders for subsequent generations were selected after weaning of the second mating from each generation. There were no compound-related adverse effects on reproductive indices and no gross anomalies were observed. The body weights of parents and pups were significantly reduced (P less than 0.05) in all generations at the 4.0% dietary concentration. Maternal body-weight gain during gestation was frequently reduced in the 1.0 and 4.0% groups. The conservative no-observed-adverse-effect level established in this study was 0.25% (approximately 149 and 255 mg/kg body weight/day for males and females, respectively).

Comprehensive Health Effects Testing Program for Denver's Potable Water Reuse Demonstration Project

The Comprehensive Health Effects Testing Program for the Denver Water Department's Potable Water Reuse Demonstration Project is designed to evaluate the relative health effects of highly treated reclaimed water derived from secondary wastewater compared to Denver's present high-quality drinking water. The 1 million gallon per day (1 mgd) demonstration plant provides water to be evaluated in the studies treating unchlorinated secondary treated wastewater with the following additional processes: high pH lime clarification, recarbonation, filtration, ultraviolet irradiation, activated carbon adsorption, reverse osmosis, air stripping, ozonation, and chloramination. An additional sample is obtained from the identical treatment process substituting ultrafiltration for reverse osmosis. The toxicology tests to evaluate the possible long-term health effects are chronic toxicity and oncogenicity studies in Fischer 344 rats and B6C3F1 mice and reproductive/teratology in Sprague-Dawley rats. The results of these evaluations will be correlated with microbiological, chemical, and physical test results to establish the relative quality of reclaimed water compared to all established health standards as well as Denver's pristine drinking water.

Lifetime toxicity/carcinogenicity studies of FD & C Blue No. 1 (brilliant blue FCF) in rats and mice

FD & C Blue No. 1 was fed to Charles River CD rats and CD-1 mice as a dietary admixture in lifetime toxicity/carcinogenicity studies. The rat study was conducted with an in utero phase in which the compound was administered to the F0 generation rats (60/sex/group) at dietary concentrations of 0.0%, 0.0%, 0.1%, 1.0% or 2.0%. After randomly selecting the F1 animals, the lifetime phase was initiated at the same levels with 70 rats/sex/group, including two control groups. The maximum exposure times were 116 and 111 wk for males and females, respectively. The no-observed-adverse-effect levels are dietary concentrations of 2.0% for males (1072 mg/kg body weight/day), and 1.0% for females (631 mg/kg/day) based on a 15.0% decrease in terminal body weight and decreased survival in the high-dose females compared with the combined control groups. Charles River CD-1 mice (60/sex/group) were fed FD & C Blue No. 1 as a dietary admixture at levels of 0.0%, 0.0%, 0.5%, 1.5% or 5.0% in a lifetime toxicity/carcinogenicity study. The maximum exposure time was 104 wk for both males and females. No consistent, significant compound-related adverse effects were noted. The no-observed-adverse-effect level established in this study is a dietary concentration of 5.0% (7354 mg/kg/day and 8966 mg/kg/day for male and female mice, respectively.

Interactions of water contaminants. I. Plasma enzyme activity and response surface methodology following gavage administration of CCl4 and CHCl3 or TCE singly and in combination in the rat

The joint hepatotoxicity of CCl4 and CHCl3 or TCE in male CD rats following simultaneous oral administration has been investigated. Rats with chronic indwelling arterial cannulas were administered a single oral dose of CCl4 and CHCl3 or CCl4 and TCE in 5% Emulphor at doses of 0 to 700 mg/kg. Hepatotoxicity was evaluated by measuring the activity of AST, ALT, and SDH in plasma at 0, 3, 6, 12, 24, 36, 48, and 72 hr postgavage. Response data were analyzed for interaction using response surface methodology. CCl4 alone displayed dose-dependent toxicity. TCE demonstrated little evidence of hepatotoxicity. In combination, both CCl4/CHCl3 and CCl4/TCE displayed a synergistic (supraadditive) response for peak plasma enzyme activity.

Lifetime toxicity/carcinogenicity study of FD & C Red No. 40 (allura red) in Sprague-Dawley rats

FD & C Red No. 40 was fed to Charles River CD (Sprague-Dawley) rats as a dietary admixture in a lifetime toxicity/carcinogenicity study. The study included a phase during which the colouring was administered to parental rats (30 of each sex per group) at concentrations of 0.0, 0.37, 1.39 and 5.19%, throughout the mating, gestation and lactation periods. The concurrent control group received the basal diet. After random selection of the first-generation rats, the lifetime phase was initiated using the same dietary concentrations with 50 rats of each sex per group. The maximum durations of exposure to the colouring were 118 and 121 for males and females, respectively. No compound-related adverse effects were observed, except for a reduction in body weight in high-dose females at the end of the study. The no-adverse-effect levels in this study were 5.19% (2829 mg/kg/day) for male rats, and 1.39% (901 mg/kg/day) for female rats.

A CCl4/CHCl3 interaction study in isolated hepatocytes: selection of a vehicle

Emulphor, ethanol, and dimethyl sulfoxide (DMSO) were evaluated as vehicles in studying the toxicity of CCl4 and CHCl3 in isolated hepatocytes. The appropriateness of the vehicle was determined by evaluating the following parameters: solubility of CCl4 and CHCl3 in the vehicle, cell injury (intracellular K+), cell death (LDH leakage), and lack of interaction (protection or enhanced toxicity) with CCl4 and CHCl3. The relative toxicity of the vehicles according to maximum no effect levels (v/v) was: emulphor (0.125%) greater than ethanol (1.0%) greater than DMSO (5.0%). Emulphor at toxic levels was inadequate to dissolve enough CCl4 to evaluate in this system. Ethanol (5.0, 2.5, 1.0, 0.5%) was more toxic than DMSO and interacted with both CCl4 and CHCl3 to enhance toxicity. DMSO (15.0, 5.0, 2.5%) did not significantly alter the toxicity of CCl4 and CHCl3; no interaction. These data suggest that DMSO should be the vehicle for evaluating the toxicity of CCl4 and CHCl3 and their mechanisms of action in the isolated hepatocyte.

Toxic interactions between carbon tetrachloride and chloroform in cultured rat hepatocytes

Primary cultures of adult rat hepatocytes were incubated (1.5-16 hr) with various concentrations of CCl4 (less than or equal to 0.5 mM) and/or CHCl3 (less than or equal to 2.5 mM). Agent-dependent alterations in hepatocyte functions were assessed by measuring (1) [3H]choline incorporation into phosphatidylcholine (endoplasmic reticulum), (2) MTT (tetrazolium salt) reduction (mitochondria), and (3) AST release into medium (plasma membrane). Cultured hepatocytes incubated with 0.5 mM CCl4 displayed a significant (p less than or equal to 0.001) and rapid (1.5 hr) reduction (40%) in endoplasmic reticulum function that preceded significant (p less than or equal to 0.001) alterations in mitochondria (6-16 hr) and plasma membrane (6-16 hr) functions. CCl4-dependent alterations in liver cell functions are a result of CCl4 bioactivation since metyrapone inhibits the CCl4-mediated changes in cell functions. Response surface methods (RSM) were used to determine the influence of combinations of CCl4 and CHCl3 on liver cell MTT reduction and [3H]choline incorporation. Regression coefficients were determined for CCl4, CHCl3, and CCl4-CHCl3. All results were significant (p less than 0.0001) and implied that CCl4 was a more potent hepatotoxin in vitro than CHCl3. The RSM analysis also suggested that combinations of CHCl3 and CCl4 have greater than additive effects on MTT reduction and [3H]choline incorporation. These effects of CCl4 and/or CHCl3 on liver cell functions in vitro are consistent with liver alterations observed in vivo. Therefore, primary cultures of adult rat hepatocytes may be an appropriate model in vitro to assess the hepatotoxic potential of agents alone or in combination.

Chronic toxicity/carcinogenicity studies of FD & C Yellow No. 5 (tartrazine) in rats

FD & C Yellow No. 5 was fed to Charles River CD rats as a dietary admixture in two long-term toxicity/carcinogenicity studies. The studies were conducted with an in utero phase in which the compound was administered to the F0 generation rats (60/sex/group) at levels of 0.0, 0.0, 0.1, 1.0 or 2.0% ('original study') and 0.0 or 5.0% ('high-dose study'). The concurrent control groups received the basal diet. After random selection of the F1 animals, the long-term phase was initiated using the same dietary levels with 70 rats of each sex/group, including the three control groups. The maximum exposure to the colouring was 113 and 114 wk for males and females, respectively, in the 'original' study and 122 and 125 wk for males and females, respectively, in the 'high-dose' study. No compound-related effects were noted. The no-adverse-effect level found in this study was 5.0% in the diet providing an average intake of 2641 and 3348 mg/kg/day for male and female rats, respectively.

A chronic toxicity/carcinogenicity study of FD & C Yellow No. 5 (tartrazine) in mice

Charles River CD-1 mice were fed FD & C Yellow No. 5 in the diet at levels of 0.0, 0.0, 0.5, 1.5 or 5.0% in a long-term toxicity/carcinogenicity study. Each group consisted of 60 males and 60 females. Maximum exposure was 104 wk for both males and females. No consistent, significant compound-related adverse effects were noted. The no-observed-adverse effect level established in this study was 5.0% (8103 mg/kg/day and 9735 mg/kg/day for male and female mice, respectively.)

Oral toxicology studies with xylene isomers and mixed xylenes

Xylene isomers and mixed xylenes were administered to male and female Sprague-Dawley rats to evaluate their effects on standard toxicological parameters which included body and organ weights, hematology, serum chemistries, urinalysis and histopathological examination. In the initial study, m, o- or p-xylene were administered in corn oil by gavage for 10 consecutive days at dose levels of 250, 1000 and 2000 mg/kg/day. The most noteworthy changes were increased liver weight in both sexes for all three isomers while decreases in spleen and thymus weights were seen less frequently. Rats were subsequently exposed to mixed xylenes by gavage in corn oil for 90 consecutive days at dose levels of 150, 750 and 1500 mg/kg/day. The most significant findings of the subchronic study were enlarged livers and kidneys. Histopathological evaluation of liver and kidney tissues revealed an increased incidence of minimal chronic renal disease in only female rats, while treatment related hepatic histopathological changes were not detected in either sex.

Lifetime toxicity/carcinogenicity study of FD & C Red No. 3 (erythrosine) in rats

FD & C Red No. 3 was fed to Charles River CD rats as a dietary admixture in two long-term toxicity/carcinogenicity studies. The studies consisted of an in utero and an F1 phase. In the former, the compound was administered to five groups of the F0 generation rats (60 of each sex/group) at levels of 0.0, 0.0, 0.1, 0.5 or 1.0% ('original study') and 0.0 or 4.0% ('high-dose study'). The concurrent control groups received the basal diet. After random selection of the F1 animals, the long-term phase was initiated using the same dietary levels and 70 rats of each sex/group, including the three control groups. Rats were exposed for a maximum of 30 months. No compound-related effects were noted in the in utero phase. Mean body weights of the female F1 rats on 4.0% FD & C Red No. 3 (3029 mg/kg/body weight/day) were significantly lower than those of controls (P less than 0.01) throughout the study. Food consumption increased in all treated groups in a dose-related manner. There were no significant effects on the haematology, serum chemistry and urinalysis and no compound-related effects on survival. In male rats receiving 4.0% FD & C Red No. 3 (2464 mg/kg/day) thyroid weights were increased, with a mean weight of 92 mg compared to 44 mg for controls, and statistically significant increases in the incidence of thyroid follicular cell hypertrophy, hyperplasia and adenomas were recorded. A numerically increased incidence of thyroid follicular adenomas in female rats given 0.5, 1.0 or 4.0% FD & C Red No. 3 was not statistically significant. The no-observed-adverse-effect levels established in these studies were 0.5% (251 mg/kg/day) for male rats and 1.0% (641 mg/kg/day) for females.

Lifetime toxicity/carcinogenicity study of FD & C Red No. 3 (erythrosine) in mice

Charles River CD-1 mice were fed FD & C Red No. 3 in the diet at levels of 0.3, 1.0 and 3.0% in a long-term toxicity/carcinogenicity study. Each group consisted of 60 males and 60 females. Two concurrent control groups each of 60 males and 60 females received the basal diet. Maximum exposure was 24 months. The no-adverse-effect levels established in this study were 3.0% (an average intake of 4759 mg/kg/day) for male mice and 1.0% (1834 mg/kg/day) for female mice.

Evaluation of the potential teratogenicity of FD & C Blue No. 2 in rats and rabbits

Charles River CD rats (20 pregnant rats/group) received by gavage on days 6-15 of gestation 0.5% Methocel (controls, A, B and C), retinoic acid at 7.5 mg/kg/day or FD & C Blue No. 2 in doses of 25, 75 or 250 mg/kg/day. Pregnant Dutch belted rabbits (ten pregnant does/group) received by gavage on days 6-18 of gestation 0.5% Methocel (controls A, B and C), thalidomide at 150 mg/kg/day or FD & C Blue No. 2 in doses of 25, 75 or 250 mg/kg/day. All animals were observed twice daily during gestation for signs of toxicity. The animals were killed 1 day before term and appropriate maternal and foetal parameters were evaluated. There were no consistent, significant compound-related adverse effects on any of these parameters. Foetal malformations occurred in both positive control groups. Under the conditions of this study, FD & C Blue No. 2 did not exert any teratogenicity or other developmental toxicity in either rats or rabbits.

Toxicology of haloacetonitriles

Haloacetonitriles are by-products of water chlorination and may form in vivo from the reaction of residual chlorine with endogenous compounds such as amino acids. Dibromoacetonitrile (DBAN) was negative in selected mutagenic assays; dichloroacetonitrile (DCAN) was mutagenic in S. typhimurium, but not in S. cerevisiae. Both DBAN and DCAN may be carcinogenic. There is a paucity of basic toxicological data for these compounds. The studies described were conducted to determine the acute, subacute, and subchronic toxicity of DBAN and DCAN. The acute oral LD50 values (mg/kg) in mice and rats are: DBAN, mice: 289 (M), 303 (F); DBAN, rats: 245 (M), 361 (F); DCAN, mice: 270 (M), 279 (F); DCAN, rats: 339 (M), 330 (F). Death was preceded by slowed respiration, depressed activity, prostration, and coma. There were no apparent compound-related gross pathological effects. DBAN (in corn oil) was administered by gavage to male and female CD rats for 14 or 90 days at levels of 23, 45, 90, and 180 mg/kg/day or 6, 23, and 45 mg/kg/day, respectively. Mortality was 100% at 180 mg/kg and 40% (M) and 20% (F) at 90 mg/kg/day. Compound-related mortality was 10% (M) and 5% (F) at 45 mg/kg and 0% (M) and 10% (F) at 23 mg/kg during the 90-day study. No consistent, significant, adverse compound-related effects on any of the parameters evaluated were evident. Possible target organs might be spleen, thymus, and liver. The no-observed adverse-effect level (NOAEL) for 14 days was 45 mg/kg/day and for 90 days was 23 mg/kg/day. DCAN (in corn oil) was administered by gavage to male and female CD rats for 14 or 90 days at levels of 12, 23, 45, and 90 mg/kg/day or 8, 33, and 65 mg/kg/day, respectively. There were no deaths during the 14-day study. Compound-related mortality was 50% (M) and 25% (F) at 65 mg/kg, 10% (M) and 5% (F) at 33 mg/kg, and 5% (M) and 0% (F) at 8 mg/kg during the 90-day study. Body weights were significantly lower at 90 and 65 mg/kg/day; weight and ratios of spleen and gonads and cholesterol levels were significantly lower at 90 mg/kg/day. No consistent, significant adverse compound-related effects on any of the parameters evaluated were evident. The NOAEL for 14 days was 45 mg/kg/day and for 90 days was 8 mg/kg/day.

Acute, 14-day repeated dosing, and 90-day subchronic toxicity studies of carbon tetrachloride in CD-1 mice

CD-1 mice received carbon tetrachloride daily by gavage for 14 or 90 consecutive days. Corn oil was the vehicle used. The 14-day study involved doses of 625, 1250, and 2500 mg/kg; the 90-day subchronic study involved doses of 12, 120, 540, and 1200 mg/kg. The 14-day study revealed a dose-dependent mortality and decreased body weight in males, whereas females demonstrated mortality only at the high dose. Other dose-dependent findings included decreased fibrinogen and lymphocytes; increased LDH, SGPT (ALT), and SGOT (AST); increased liver weights and ratios in both sexes; and decreased lung, thymus, and kidney weights in males only. There were no compound-related deaths in the 90-day study. There were no consistent compound-related effects on any of the hematological or urinary parameters evaluated. LDH, SGPT (ALT), SGOT (AST), ALP, cholesterol, and bilirubin were increased in an apparent dose-dependent manner while blood glucose levels decreased at all dosage levels. Liver, spleen, and thymus weights and ratios were increased at all dosage levels in both sexes. Histopathology revealed no kidney damage, but liver damage was observed at all doses in both sexes. A no-observable-adverse-effect level was not obtained in these studies.

Acute, 14-day repeated dosing, and 90-day subchronic toxicity studies of potassium picloram

Potassium picloram was administered either by gavage (acute studies) or in drinking water to male and female Sprague-Dawley-derived rats (14-day and 90-day studies). The acute oral LD50 was 950 mg/kg (812-1120) for males and 686 mg/kg (599-786) for females. Depression, prostration, ataxia, tremors, and convulsions preceded death. There were no consistent biologically significant compound-related effects in rats that received 60, 190, 600 mg potassium picloram/kg/day for 14 days. In the subchronic study, rats received 60, 190, 600, or 1070 mg potassium picloram/kg/day in drinking water for 90 consecutive days. There were only 4 male and 2 female survivors out of 20 rats of each sex at the 1070 mg/kg dose and 16 male and 18 female survivors at the 600 mg/kg dose. Mortality was dose dependent. Administration of picloram appeared to exacerbate renal and hepatic lesions commonly noted in rats of this age. For example, at levels up to 1070 mg/kg mild lesions in the kidney of treated rats, especially in males at 600 mg/kg, were noted. Also noted were an increased incidence of mononuclear liver foci in male rats that received 190 and 600 mg/kg and an increased severity of mononuclear liver foci in females that received 600 mg/kg. There were no other consistent biologically significant compound-related effects. No specific organ site toxicity could be identified in these studies. Toxicity from exposure to picloram in drinking water is apparently low.

Effect of in vitro differentiation on phorbol diester receptor number in human promyelocytic leukemia (HL-60) cells

Phorbol diester (PDE) tumor promoters affect cells by interacting with specific receptors on the plasma membrane. Cells are known to regulate their receptor populations in response to many external and internal stimuli, including differentiation. The human promyelocytic leukemia cell line HL-60, which can be induced by dimethyl sulfoxide to differentiate into mature granulocytes, was used as a model to examine whether PDE receptors are regulated as cells differentiate in vitro. PDE binding was measured using [20-3H]phorbol 12,13-dibutyrate ([3H]PDBu). Specific binding of [3H]PDBu to the undifferentiated cells was rapid, reversible, and time and concentration related. One class of noncooperative binding sites was found with approximately 3.3 X 10(5) cells, having a Kd of 27.5 nM. [3H]PDBu could be displaced from the binding sites by a series of biologically active PDEs, but not by inactive ones. The characteristics of [3H]PDBu binding to the differentiated HL-60 cells were almost identical to those of the undifferentiated cells, except that there was an increase in the number of binding sites to 9.1 X 10(5) cells. Production of reactive oxygen metabolites by the cells, as monitored by chemiluminescence (CL) in response to PDEs, was examined before and after dimethyl sulfoxide differentiation, to determine if the change in receptor density was accompanied by a change in cell function. Only the differentiated HL-60 cells produced a quantifiable CL response when exposed to PDEs. The potency of the PDEs in causing CL generation was the same as that for displacing [3H]PDBu. The correlation between CL generation and affinity for the binding site suggests that the PDE binding sites mediate this effect of the PDEs and, therefore, are receptors. These studies indicate that HL-60 cells regulate their PDE receptors as they differentiate in vitro, with minimal extracellular influence. This may reflect a portion of an internal mechanism to enhance or change response to an endogenous ligand for the PDE receptor as cells mature.

The subchronic toxicity of tetrachloroethylene (perchloroethylene) administered in the drinking water of rats

This study provides data on the effects of tetrachloroethylene in drinking solutions. The acute oral LD50 in male and female Charles River rats was found to be 3835 mg/kg for males and 3005 mg/kg for females. Male and female rats received theoretical daily doses of 14,400, and 1400 mg tetrachloroethylene/kg body wt/day for 90 consecutive days. There were no compound-related deaths. Body weights were significantly lower in male and female rats at the higher doses. There were no consistent dose-related effects on any of the hematological, clinical chemistry, or urinalysis parameters. 5'-Nucleotidase activity was increased in a dose-dependent manner, suggesting possible hepatotoxicity; however, other serum indicators of hepatic function were unaffected by the treatment. There were no gross pathological effects observed. Liver and kidney body weight ratios, but not brain weight ratios, were elevated at the higher doses. There was no other evidence of compound-related toxicity. These data suggest that exposure of humans to reported levels of tetrachloroethylene in drinking water (approximately 1 microgram/liter) does not constitute a serious health hazard.