Bernard D. Astill

Peroxisome Induction Studies On Seven Phthalate Esters

Seven phthalate esters, representing a variety of chain lengths and degrees of branching in the alcohol moiety, were tested for their ability to produce peroxisome proliferation in the Fischer 344 rat. Di(2-ethylhexyl)adipate (DEHA) was tested using the same protocol and di(2-ethylhexyl)phthalate (DEHP) was run with each study as an internal control. Each ester was administered in the feed for a period of 21 days at levels of 2.5%, 1.2% and either 0.6% or 0.3%. DEHP and DEHA were also fed at levels of 0.1% and 0.01%. The animals were sacrificed and samples of liver were prepared for both light and electron microscopy. Serum samples were assayed for both triglyceride and cholesterol. The remaining portion of the liver was homogenized and assayed for cyanide-insensitive palmitoyl-CoA oxidation, lauric acid 11-hydroxylase and lauric acid 12-hydroxylase. The results show that there is approximately a ten-fold difference between the weakest and strongest esters in terms of their potency to induce changes in relative liver weight and in several of the biochemical parameters. In general, the longer chain esters were more potent than the shorter chain ones, and branched chain esters seemed more potent than straight. Several statistical analyses of the dataset have been performed and all render similar conehcsions. The results of one of these evaluations are presented elsewhere in this volume (Lin, 1987).

Human and Canine Exposures to Methylene Chloride Vapor

Well-controlled experimental exposures to methylene chloride vapor lasting for 2 or 4 hours were performed in human beings and dogs. The exposure concentrations ranged from 100 to 1000 ppm in the dogs and from 100 to 200 ppm in man. Serial breath and blood curves from both species were directly proportional to the magnitude of exposure. The average 24-hour urinary excretions of methylene chloride for the 100- and 200-ppm exposures in man were approximately 23 µg and 82 µg, respectively. During comparable exposures the dog absorbed substantially more methylene chloride vapor than man. Prolonging the exposure from 2 to 4 hours did not result in a substantial increase in solvent absorption. These studies have demonstrated that it is possible to make accurate extrapolations to human exposures from animal experiments provided the appropriate attention is given to factors such as the exposure duration, the time of collection after the exposure, the extent of metabolic involvement, and kinetic parameters. In suc...

Exposure of Man and Dog to Low Concentrations of Acetone Vapor

Experimental exposures to acetone vapor were carried out in man and dog to compare the behavior of acetone in each species. Although acetone has been studied quite extensively, low-level vapor exposures are not well documented in the literature. Exposures were conducted for 2 or 4 hours at concentrations of 100 and 500 ppm with human subjects and at 100, 500, and 1000 ppm with dogs. In both species the concentrations of acetone in the breath and blood were found to be directly proportional to the magnitude of the exposure. In the human studies casual urine samples were collected for 24 hours; no direct proportionality between urinary acetone and exposure level was found. With comparable exposures, man absorbed a greater quantity of acetone than the dog. In both species the half-life of acetone in the blood was approximately the same (3 hours). In man exercise substantially increased the extent of acetone absorption. When the exposure was extended from 2 to 4 hours, less than a twofold increase in the post...

Results of the l5178y mouse lymphoma assay and the balb/3t3 cell in vitro transformation assay for eight phthalate esters

Eight phthalate esters, with alcohol chain lengths of 1–11 carbon atoms and with various degrees of branching, were tested in vitro in the L5178Y mouse lymphoma mammalian cell mutation assay and in the Balb/3T3 cell transformation assay. The tests were performed as part of a voluntary testing agreement between the Chemical Manufacturers Association’s Phthalate Esters Panel and the United States Environmental Protection Agency (US EPA). The esters tested were: dimethyl phthalate (DMP), di‐n‐butyl phthalate (DBP), butyl benzyl phthalate (BBP), di‐{n‐hexyl, n‐octyl, n‐decyl} phthalate (610P), di‐isononyl phthalate (DINP), di‐{heptyl, nonyl, undecyl} phthalate (711P), di‐isodecyl phthalate (DIDP) and di‐undecyl phthalate (DUP). Both DMP and DBP were found to produce significant increases in the mutant frequency in the mouse lymphoma assay in the presence but not in the absence of an Aroclor‐induced rat liver activation system (S‐9). Ester 610P gave equivocal results in the mouse lymphoma assay in the presence and absence of rat liver S‐9. There was no indication of mutagenic potential for any of the other test materials in the mouse lymphoma assay, and none of the test materials increased transformation frequency in the Balb/3T3 cell transformation assay. Aldehyde metabolites of the de‐esterified alcohols are postulated to play a role in the positive results for DMP and DBP. Copyright

Phenolic antioxidants and the inhibition of hepatotoxicity from N-dimethylnitrosamine formed in situ in the rat stomach.

Abstract The effect of the widely used edible stabilizers propyl gallate (PG), butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and tert -butylhydroquinone (TBHQ) on intragastric N -nitrosamine formation was studied. Rats were given by gastric intubation, sodium nitrite (125 mg/kg) and dimethylamine (1000 mg/kg) followed immediately by the test compound in doses of 25, 75 or 225 mg/kg. Ascorbate (200 mg/kg) was used as a positive control. Indices of N -nitrosamine formation 48 hr after dosing were the activities of serum glutamic-oxalacetic transaminase (GOT) glutamic-pyruvic transaminase (GPT), and ornithine-carbamoyl transferase (OCT), and the extent of hepatic necrosis. The nitrosamine-forming mixture alone produced extensive hepatic necrosis and 24-, 19- and 4-fold increases in serum GOT, GPT and OCT activities respectively. Enzyme induction was completely suppressed by ascorbate. PG completely protected against hepatic necrosis and enzyme induction at 225 mg/kg, and to a lesser extent at 75 mg/kg. TBHQ gave 60% protection against necrosis and appreciably suppressed enzyme activity increases at 225 mg/kg. BHA and BHT at all dose levels, PG at 25 mg/kg and TBHQ at 25 and 75 mg/kg neither demonstrated protective activity nor induced any lethality. Hence at approximately equimolar levels of nitrite and antioxidant, PG and TBHQ exerted an inhibitory effect on nitrosamine formation, but at lower levels all four antioxidants tested had no observable effect on the nitrosamine-forming system.

Absorption of methyl-2-cyanoacrylate-2-14C from full-thickness skin incisions in the Guinea pig and its fate in vivo

Summary Methyl-2-cyanoacrylate-2-14C polymerized in vivo as a tissue adhesive in guinea pigs was absorbed readily and eliminated by the body. Removal from the site of skin incisions was virtually complete by 107 days and only a trace of radioactivity was detectable at that time.

The Gas Chromatographic Analysis of Methylene Chloride in Breath, Blood, and Urine

The analysis of low concentrations of certain volatile organic solvents in breath, blood, and urine can be performed entirely on a gas chromatograph equipped with a gas sample valve. Breath samples from human subjects exposed to methylene chloride were collected in Saran bags; blood and urine were placed directly into sealed flasks. A structural modification of the gas sample valve enabled a heated flask to be inserted into the gas sampling system, resulting in the direct measurement of the head space vapors. These procedures are rapid, simple, and generally applicable to the analysis of several volatile organic compounds either discretely or simultaneously.

The toxicology and fate of 2,2,4-trimethyl-1,3-pentanediol diisobutyrate.

Abstract Since 2,2,4-trimethyl-1,3-pentanediol diisobutyrate (TXIB) may be an indirect food additive because of its use in food packaging, a study was made of its toxicology and fate. Acute po, ip, skin irritation, sensitization and inhalation studies showed it to be practically nontoxic, a slight skin irritant and not a sensitizer. Rats were fed concentrations of 0.1 and 1.0% in their diet for 103 days. The only consistent finding was a slight but significant increase in the weight of the livers of rats fed 1.0% TXIB. Dogs fed for 90 days at concentrations of 0.1, 0.35 and 1.0% in the diet showed only slight increases in some of the liver weights and a slight increase in the average pituitary weight of males at the highest dose levels. Single po 250 mg/kg doses of 3- 14 C-labeled-TXIB were eliminated within 7–10 days of dosing almost completely in the urine (47–73%) and feces (27–46%), 80% being eliminated within 4 days. 14 CO 2 excretion was insignificant. At sacrifice after 14 days these doses, and 1 of about 900 mg/kg, gave negligible increments of radioactivity in liver, brain, kidneys, lungs and fat. After TXIB dosing, free 2,2,4-trimethylpentane-1,3-diol (TMPD), 2,2,4-trimethyl-3-hydroxyvaleric acid (HTMV), their glucuronides, and a monoisobutyrate of 2,2,4-trimethylpentane-1,3-diol were found in the urine. Feces contained the same monoisobutyrate and unchanged TXIB.

The fate of 2,6-bis-(1′-methyl-14C-heptadecyl)-p-cresol (dioctadecyl-p-cresol-14C) in the rat

Abstract The fate of DOPC, 2,6-bis-(1′-methylheptadecyl)-p-cresol, a hindered phenol intended for use as a stabilizer in food packaging, has been studied in rats. Following oral ingestion of 1.0 g/kg doses there are no significant increases in urinary conjugate output, and a large proportion of the dose appears to be unabsorbed. The ingestion of DOPC-14C-labeled on both 1′-methyl carbon atoms as single undiluted 190–860 mg/kg oral doses is followed by the rapid excretion of almost the entire dose in the feces, 96–100% of the dose being thus accounted for within 3–5 days. Less than 1.0% is accounted for in the urine, and none is detectable in the expired air. The fate of DOPC-14C incorporated in the diet at the 0.01% level and ingested for 15 days is identical with that of large single doses. Traces of radioactivity are disseminated to brain, fat, kidney, and liver at higher single dose levels, to liver at lower single dose levels and to brain and liver after ingestion in the diet. This radioactivity is released at varying rates from the respective tissues and is not retained.

The fate of [14C]thiodipropionates in rats

Abstract Thiodipropionic acid and its esters are preservatives and stabilizers used in food and food packaging. The oral fate in rats, hitherto unknown, of thiodipropionic acid (TDPA), didodecyl thiodipropionate (DDTDP), and of a polyester of thiodipropionic acid with cyclohexane-1,4-dimethanol partially terminated with stearyl alcohol, POLY-TDPS-2000 (TDPS), was elucidated in evaluating TDPS as a polymer stabilizer. Single doses of [1- 14 C]TDPA were rapidly eliminated, 87–95% of 241–650 mg/kg doses being recovered in 4 days in urine (78–88%), and feces (0.1–0.9%) and as 14 CO 2 (3–8%). Radioactivity in tissues and organs was less than 1.5 × background. A 3-mg/kg dose of [1- 14 C]TDPA was handled similarly. Urinary radioactivity at the higher dose was due almost entirely to unchanged TDPA, while the lower dose apparently gave an acid-labile conjugate of TDPA. Single oral doses of [1- 14 C]DDTDP (107 and 208 mg/kg) were rapidly eliminated, mostly in the urine (85–88%), with less in feces (1.8–3.5%) and as 14 CO 2 (3–4%, by day 4); 1-day dietary feeding of 166 mg/kg gave similar results. Tissue and organ levels of radioactivity at sacrifice were close to background, with the exception of fat levels, which were elevated 34 days after dosing. Urinary radioactivity was mostly unchanged TDPA or an acid-labile conjugate. Five-hour feeding in the diet of each of 3 rats of 4.7–5.6 mg/kg of 14 C-labeled TDPS prepared from [1- 14 C]TDPA, was almost entirely eliminated by 4 days in urine (95%) and feces (0.7%) and as 14 CO 2 (approx. 6%). At sacrifice 4 days after dosing, tissue and organ radioactivity was slightly above background, and at 34 days essentially normal. Almost two-thirds of the urine radioactivity was due to [1- 14 C]TDPA or a conjugate. TDPA is in many respects similar to a typical dicarboxylic acid after oral intake in being rapidly absorbed and eliminated in the urine largely unchanged. Simple esters and polyesters of TDPA appear to be readily hydrolyzed in the organism to the parent acid, which is then eliminated similarly to TDPA given orally.