Impact of Acrylamide on Calcium Signaling and Cytoskeletal Filaments in Testes From F344 Rat.

Acrylamide (AA) at high exposure levels is neurotoxic, induces testicular toxicity, and increases dominant lethal mutations in rats. RNA-sequencing in testes was used to identify differentially expressed genes (DEG), explore AA-induced pathway perturbations that could contribute to AA-induced testicular toxicity and then used to derive a benchmark dose (BMD). Male F344/DuCrl rats were administered 0.0, 0.5, 1.5, 3.0, 6.0, or 12.0 mg AA/kg bw/d in drinking water for 5, 15, or 31 days. The experimental design used exposure levels that spanned and exceeded the exposure levels used in the rat dominant lethal, 2-generation reproductive toxicology, and cancer bioassays. The time of sample collection was based on previous studies that developed gene expression-based BMD. At 12.0 mg/kg, there were 38, 33, and 65 DEG ( P value <.005; fold change >1.5) in the testes after 5, 15, or 31 days of exposure, respectively. At 31 days, there was a dose-dependent increase in the number of DEG, and at 12.0 mg/kg/d the top three functional clusters affected by AA exposure were actin filament organization, response to calcium ion, and regulation of cell proliferation. The BMD lower 95% confidence limit using DEG ranged from 1.8 to 6.8 mg/kg compared to a no-observed-adverse-effect-level of 2.0 mg/kg/d for male reproductive toxicity. These results are consistent with the known effects of AA on calcium signaling and cytoskeletal actin filaments leading to neurotoxicity and suggest that AA can cause rat dominant lethal mutations by these same mechanisms leading to impaired chromosome segregation during cell division.

Integrating Bar-Code Medication Administration Competencies in the Curriculum: Implications for Nursing Education and Interprofessional Collaboration.

This article describes an innovative project involving the integration of bar-code medication administration technology competencies in the nursing curriculum through interprofessional collaboration among nursing, pharmacy, and computer science disciplines. A description of the bar-code medication administration technology project and lessons learned are presented.

Differential genotoxicity of acrylamide in the micronucleus and Pig-a gene mutation assays in F344 rats and B6C3F1 mice.

Acrylamide is used in many industrial processes and is present in a variety of fried and baked foods. In rodent carcinogenicity assays, acrylamide exposure leads to tumour formation at doses lower than those demonstrated to induce genotoxic damage. We evaluated the potential of acrylamide to induce structural DNA damage and gene mutations in rodents using highly sensitive flow cytometric analysis of micronucleus and Pig-a mutant frequencies, respectively. Male F344 rats and B6C3F1 mice were administered acrylamide in drinking water for 30 days at doses spanning and exceeding the range of acrylamide exposure tested in cancer bioassays-top dose of 12.0 and 24.0mg/kg/day in mice and in rats, respectively. A positive control, N-ethyl-N-nitrosourea, was administered at the beginning and end of the study to meet the expression time for the two DNA damage phenotypes. The results of the micronucleus and Pig-a assays were negative and equivocal, respectively, for male rats exposed to acrylamide at the concentrations tested. In contrast, acrylamide induced a dose-dependent increase in micronucleus formation but tested negative in the Pig-a assay in mice. Higher plasma concentrations of glycidamide in mice than rats are hypothesized to explain, at least in part, the differences in the response. Benchmark dose modelling indicates that structural DNA damage as opposed to point mutations is most relevant to the genotoxic mode of action of acrylamide-induced carcinogenicity. Moreover, the lack of genotoxicity detected at <6.0mg/kg/day is consistent with the notion that non-genotoxic mechanisms contribute to acrylamide-induced carcinogenicity in rodents.

Transcriptomics analysis and hormonal changes of male and female neonatal rats treated chronically with a low dose of acrylamide in their drinking water.

Acrylamide is known to produce follicular cell tumors of the thyroid in rats. RccHan Wistar rats were exposed in utero to a carcinogenic dose of acrylamide (3 mg/Kg bw/day) from gestation day 6 to delivery and then through their drinking water to postnatal day 35. In order to identify potential mechanisms of carcinogenesis in the thyroid glands, we used a transcriptomics approach. Thyroid glands were collected from male pups at 10 PM and female pups at 10 AM or 10 PM in order to establish whether active exposure to acrylamide influenced gene expression patterns or pathways that could be related to carcinogenesis. While all animals exposed to acrylamide showed changes in expected target pathways related to carcinogenesis such as DNA repair, DNA replication, chromosome segregation, among others; animals that were sacrificed while actively drinking acrylamide-laced water during their active period at night showed increased changes in pathways related to oxidative stress, detoxification pathways, metabolism, and activation of checkpoint pathways, among others. In addition, thyroid hormones, triiodothyronine (T3) and thyroxine (T4), were increased in acrylamide-treated rats sampled at night, but not in quiescent animals when compared to controls. The data clearly indicate that time of day for sample collection is critical to identifying molecular pathways that are altered by the exposures. These results suggest that carcinogenesis in the thyroids of acrylamide treated rats may ensue from several different mechanisms such as hormonal changes and oxidative stress and not only from direct genotoxicity, as has been assumed to date.

Dosimetry of Acrylamide and Glycidamide Over the Lifespan in a 2-Year Bioassay of Acrylamide in Wistar Han Rats.

Acrylamide is an industrial chemical used to manufacture polymers, and is produced in foods during cooking at high heat. Hemoglobin adducts provide a long-lived dosimeter for acrylamide and glycidamide. This study determined acrylamide and glycidamide hemoglobin adducts (AAVal and GAVal) during a lifetime carcinogenesis bioassay. Exposure to acrylamide in drinking water began in utero in pregnant rats on gestation day 6. Dams were administered acrylamide until weaning, and male and female F1 rats were exposed for a further 104 weeks. Acrylamide concentration in drinking water was adjusted to provide a constant dose of 0.5, 1.5, and 3 mg/kg/day. Blood was collected from animals euthanized at 2, 60, 90, and 120 days and 53, 79, and 104 weeks after weaning. Low levels of AAVal and GAVal at postnatal day 24 suggested that little exposure to acrylamide occurred by placental or lactational transfer, and extensive metabolism to glycidamide occurred with a GAVal:AAVal ratio of 4. Adduct levels varied somewhat from 60 days to 2 years, with a GAVal:AAVal ratio of approximately 1. Adduct formation/day estimated at each timepoint at 3 mg/kg/day for AAVal was 1293 ± 220 and 1096 ± 338 fmol/mg/day for male and female rats, respectively. Adduct formation per day estimated at each timepoint at 3 mg/kg/day for GAVal was 827 ± 78 fmol/mg/day for male rats, and 982 ± 222 fmol/mg/day for female rats. The study has provided estimates of linearity for dose response, and variability in internal dose throughout an entire 2-year bioassay, including the early phases of pregnancy and lactation.

Very low-activity stress/high-activity rest, single-day myocardial perfusion SPECT with a conventional sodium iodide camera and wide beam reconstruction processing.

BACKGROUND: A stress (S)/rest (R) 1-day Tc-99m sestamibi protocol is logistically advantageous and facilitates stress-only imaging. However, with conventional 370 MBq (10 mCi) S activity and subsequent 1,110-1,295 MBq (30-35 mCi) R activity there is a risk of S-to-R "shine-through" and underestimation of defect reversibility. New software methods cope with lower counting statistics and should allow for both a reduced S activity and also less likelihood of S-to-R "shine-through." METHODS: 102 prospective patients [49 men, 53 women; mean weight 178 ± 41 lbs (range 98-265 lbs); chest 41.5″ ± 4.0″ (range 32″-52″)] received 192.4 + 18.5 MBq (5.2 ± 0.5 mCi) Tc-99m sestamibi S (25 exercise, 77 regadenoson) activity followed in 30-40 minutes by "full-time" (12 minutes) two-headed NaI camera S SPECT. Immediately thereafter, a 16-minute S SPECT acquisition was also performed in 37/102 patients. Then at 60-80 minute post-S all patients received 1328.3 + 129.5 MBq (35.9 ± 3.5 mCi) Tc-99m sestamibi, and "half-time" (7.5 minutes) R SPECT was acquired. All tomograms were processed with wide beam reconstruction (WBR, UltraSPECT Ltd.) software. A time-adjusted R/S myocardial count density ratio (MCDR) was calculated using automated software. S SPECT quality was visually graded (poor, fair, good, excellent) based upon myocardial definition, cavity contrast, RV visualization, and noise. For comparison, the S/R MCDR was calculated in 581 consecutive patients undergoing a conventional 370 MBq R/1110 MBq S (10 mCi R/30 mCi S) protocol. RESULTS: S SPECT was normal in 44 patients (43%). Image quality was good-excellent in 93 (91%) patients with 12-minute S SPECT. Also in 37 (98%) patients with 16-minute S SPECT, quality was good-excellent. In patients with >42″ chests 12-minute S SPECT quality worsened with increasing chest circumference, manifested by myocardial "blurring." Image quality improved by ≥1 grade in the 12/37 patients (32%) also undergoing 16-minute S SPECT. The time- and decay-corrected 12-minute mean R/S MCDR was 5.78, a ratio adequate to minimize S-to-R shine-through, as verified in phantom experiments, and significantly better than a 3.79 S/R ratio achieved in the 581 patients undergoing a conventional R/S protocol. CONCLUSIONS: An approximately 185 MBq (5 mCi S) Tc-99m SPECT processed with WBR provides adequate image quality. For larger patients prolonging image acquisition to 16 minutes is beneficial. For patients with normal S SPECT, a S-only protocol is feasible, affording them a very low (approximately 1.4 mSv) radiation dose. If subsequent R SPECT is necessary, it can be performed with approximately 1,332 MBq (36 mCi) with minimal S-R "shine-through."

A comparison of the image quality of full-time myocardial perfusion SPECT vs wide beam reconstruction half-time and half-dose SPECT.

OBJECTIVES: Wide Beam Reconstruction (WBR) (UltraSPECT, Ltd) uses resolution recovery and noise modeling to cope with decreased SPECT count statistics. Because WBR processing reconstructs half the usual SPECT count statistics, we postulate that image quality equivalent to a full-time acquisition can be achieved in either half the time or with half the radiopharmaceutical activity. METHODS: In 156 consecutive patients (pts) rest and 8-frame gated post-stress myocardial perfusion SPECT was performed following 333-444 and 1184-1480 MBq (9-12 and 32-40 mCi) Tc-99m sestamibi injections, respectively, with full-time (rest = 14 min; stress = 12.3 min) acquisitions processed with OSEM and also separate "half-time" acquisitions processed with WBR. A subsequent group of 160 consecutive pts matched in gender, weight, and chest circumference received "half-dose" rest and stress injections 214.6 ± 22.2 and 647.5 ± 92.5 MBq (5.8 ± 0.6 and 17.5 ± 2.5 mCi) with full-time SPECT acquisitions. Image quality (1 = poor to 5 = excellent) was judged by myocardial count density and uniformity, endocardial edge definition, perfusion defect delineation, right ventricular visualization, and background noise. RESULTS: Mean image quality for rest, stress, and post-stress gated images were 3.6 ± 0.7, 3.8 ± 0.7, and 3.9 ± 1.0, respectively, for "full-time OSEM; 3.7 ± 0.8, 4.0 ± 0.7, and 4.8 ± 0.4 for "half-time" WBR; and 4.3 ± 0.8, 4.6 ± 0.6, and 4.7 ± 0.6 for "half-dose" WBR. "Half-time" and "half-dose" WBR image quality were both superior to standard full-time OSEM (P's < .001). There was no significant difference between the summed stress and rest scores for "full-time" OSEM vs "half-time" WBR in 82 patients with perfusion defects. CONCLUSIONS: Both "half-time" and "half-dose" WBR provide myocardial perfusion SPECT quality superior to full-time OSEM, with an associated decrease in scan acquisition time and patient radiation exposure, respectively.

Investigation of the low-dose response in the in vivo induction of micronuclei and adducts by acrylamide.

Acrylamide is an industrial chemical used in polymer manufacture. It is also formed in foods processed at high temperatures. It induces chromosome aberrations and micronuclei (MN) in somatic cells of mice, but not rats, and mutations in transgenic mice. This study evaluated the low-dose MN response in mouse bone marrow and the shape of the dose-response curve. Mice were treated orally with acrylamide for 28 days using logarithmically spaced doses from 0.125 to 24 mg/kg/day, and MN were assessed in peripheral blood reticulocytes (RETs) and erythrocytes by flow cytometry. Liver glycidamide DNA adducts and acrylamide and glycidamide N-terminal valine hemoglobin adducts were also determined. Acrylamide produced a weak MN response, with statistical significance at 6.0 mg/kg/day, or greater, in MN-RETs and at 4.0 mg/kg/day or greater in MN normochromatic erythrocytes (NCEs). The MN responses at the lower doses were indistinguishable from the concurrent and historical controls. The adducts increased at a much different rate than the MN. When the MN-NCE values were compared to administered dose, the response was consistent with a linear model. However, when hemoglobin or DNA adducts were used as the dose metric, the response was significantly nonlinear, and models that assumed a threshold dose of 1 or 2 mg/kg/day provided a better fit than a linear model. The MN-RET dose-response had greater variability than the MN-NCE response and was consistent with linearity and with a threshold at 1 or 2 mg/kg/day, regardless of the dose metric. These data suggest a threshold for acrylamide in the MN test.

Inhibition of rat testicular nuclear kinesins (krp2; KIFC5A) by acrylamide as a basis for establishing a genotoxicity threshold.

Acrylamide is a toxic substance that induces a variety of cellular responses including neurotoxicity, male reproductive toxicity, tumorigenicity, clastogenicity, and DNA alkylation. Evidence is provided that inhibition of the microtubule motor protein kinesin is responsible for acrylamide-induced clastogenicity and aneuploidy. Two kinesin motors, KIFC5A and KRP2, which are responsible for spindle assembly and disassembly of kinetochore MT, respectively, are inhibited by acrylamide. The inhibitory concentration for a response is below the levels shown to adversely affect the cytogenetic parameters. The relative contribution of these inhibitions compared to DNA alkylation is considered. The implications of inhibition of these kinesins as the site of action of acrylamide with regard to risk assessment are substantial as this event will have a threshold and a safe level of acrylamide can be determined.

Acrylamide does not induce tumorigenesis or major defects in mice in vivo.

Chronic administration of acrylamide has been shown to induce thyroid tumors in rat. In vitro acrylamide also causes DNA damage, as demonstrated by the comet assay, in various types of cells including human thyroid cells and lymphocytes, as well as rat thyroid cell lines. In this work, mice were administered acrylamide in their drinking water in doses comparable with those used in rats, i.e., around 3-4 mg/kg per day for mice treated 2, 6, and 8 months. Some of the mice were also treated with thyroxine (T(4)) to depress the activity of the thyroid. Others were treated with methimazole that inhibits thyroid hormone synthesis and consequently secretion and thus induces TSH secretion and thyroid activation. These moderate treatments were shown to have their known effect on the thyroid (e.g. thyroid hormone and thyrotropin serum levels, thyroid gland morphology...). Besides, T(4) induced an important polydipsia and degenerative hypertrophy of adrenal medulla. Acrylamide exerted various discrete effects and at high doses caused peripheral neuropathy, as demonstrated by hind-leg paralysis. However, it did not induce thyroid tumorigenesis. These results show that the thyroid tumorigenic effects of acrylamide are not observed in another rodent species, the mouse, and suggest the necessity of an epidemiological study in human to conclude on a public health policy.

Acrylamide effects on kinesin-related proteins of the mitotic/meiotic spindle.

The microtubule (MT) motor protein kinesin is a vital component of cells and organs expressing acrylamide (ACR) toxicity. As a mechanism of its potential carcinogenicity, we determined whether kinesins involved in cell division are inhibited by ACR similar to neuronal kinesin [Sickles, D.W., Brady, S.T., Testino, A.R., Friedman, M.A., and Wrenn, R.A. (1996). Direct effect of the neurotoxicant acrylamide on kinesin-based microtubule motility. Journal of Neuroscience Research 46, 7-17.] Kinesin-related genes were isolated from rat testes [Navolanic, P.M., and Sperry, A.O. (2000). Identification of isoforms of a mitotic motor in mammalian spermatogenesis. Biology of Reproduction 62, 1360-1369.], their kinesin-like proteins expressed in bacteria using recombinant DNA techniques and the effects of ACR, glycidamide (GLY) and propionamide (a non-neurotoxic metabolite) on the function of two of the identified kinesin motors were tested. KIFC5A MT bundling activity, required for mitotic spindle formation, was measured in an MT-binding assay. Both ACR and GLY caused a similar concentration-dependent reduction in the binding of MT; concentrations of 100 microM ACR or GLY reduced its activity by 60%. KRP2 MT disassembling activity was assayed using the quantity of tubulin disassembled from taxol-stabilized MT. Both ACR and GLY inhibited KRP2-induced MT disassembly. GLY was substantially more potent; significant reductions of 60% were achieved by 500 microM, a comparable inhibition by ACR required a 5 mM concentration. Propionamide had no significant effect on either kinesin, except KRP2 at 10 mM. This is the first report of ACR inhibition of a mitotic/meiotic motor protein. ACR (or GLY) inhibition of kinesin may be an alternative mechanism to DNA adduction in the production of cell division defects and potential carcinogenicity. We conclude that ACR may act on multiple kinesin family members and produce toxicities in organs highly dependent on microtubule-based functions.

Kinetics of elimination of urinary metabolites of acrylamide in humans.

Acrylamide (AM), used in the manufacture of polyacrylamide and grouting agents, is produced during the cooking of foods. Workplace exposure to AM can occur through the dermal and inhalation routes. The objective of this study was to define the kinetics of elimination of AM and its metabolites following oral and dermal administration. This is the second part of a study in which metabolites and hemoglobin adducts of AM were determined in people (Fennell et al., 2005, Toxicol. Sci. 85, 447-459). (1,2,3-(13)C(3))AM was administered in an aqueous solution orally (single dose of 0.5, 1.0, or 3.0 mg/kg) or dermally (three daily doses of 3.0 mg/kg) to sterile male volunteers. Urine samples were collected at 0-2, 2-4, 4-8, 8-16, and 16-24 h following administration orally, or at 0-2, 2-4, 4-8, 8-16, and 16-24 h following each of three daily dermal doses. (13)C(3)-AM and its metabolites in urine, (13)C(3)-glycidamide, (13)C(3)-N-acetyl-S-(3-amino-3-oxopropyl)cysteine and its S-oxide, and (13)C(3)-N-acetyl-S-(3-amino-2-hydroxy-3-oxopropyl)cysteine, were quantitated using liquid chromatography-tandem mass spectrometry. The recovered urinary metabolites accounted for 45.6, 49.9, and 39.9% of a 0.5, 1.0, and 3.0 mg/kg oral dose (0-24 h), respectively, and for 4.5% of the dose after 3 mg/kg was administered daily for 3 days dermally (0-4 days). These results indicate that after oral administration AM is rapidly absorbed and eliminated. The half-life estimated for elimination of AM in urine was 3.1-3.5 h. After dermal administration, AM uptake is slow. This study indicated that skin provides a barrier that slows the absorption of AM, and results in limited systemic availability following dermal exposure to AM.

Effects of acrylamide on primary neonatal rat astrocyte functions.

The present study assessed biochemical endpoints indicative of acrylamide toxicity in astrocyte cultures derived from neonatal rat pups. Given earlier reports on the possible ability of acrylamide to induce astrocytomas in the Fischer 344 rat, we performed studies in neonatal rat astrocyte cultures from the Fischer 344 to assess the ability of acrylamide to induce astrocytic proliferation. Measurements on astrocytic proliferation included [3H]-leucine incorporation, [3H]-thymidine incorporation, and changes in proliferating cell nuclear antigen (PCNA). Although acrylamide (0.1 and 1 mM for 7, 11, 15, or 20 days) did not significantly (P > 0.05) affect [3H]-leucine or [3H]-thymidine incorporation, it significantly (P < 0.05) increased PCNA protein expression in astrocytes exposed to acrylamide for 15 and 20 days. Additional studies revealed that this effect on PCNA protein expression was not associated with activation of dopamine-2 (D2) receptors, given that quinpirole (10 microM added to cultures for the last hour of 7, 11, 15, or 20 days in culture), a selective D2 receptor agonist, did not produce results analogous to those seen with acrylamide treatment. Cotreatment of astrocytes with acrylamide (7, 11, 15, or 20 days) and the D2 receptor antagonist, sulpiride (1 microM for the last 6 h of exposure), also failed to reverse acrylamide's effect on PCNA protein induction. Taken together, these studies suggest that acrylamide promotes astrocytic cell proliferation in the CNS even though DNA synthesis did not appear stimulated.

Dose-response modeling of in vivo genotoxicity data for use in risk assessment: some approaches illustrated by an analysis of acrylamide.

Methods for dose-response modeling of in vivo genotoxicity data are introduced and applied to a case study of acrylamide. Genetic toxicity results are typically summarized as being either positive or negative, with no further consideration of the dose-response patterns that can be estimated from such studies. This analysis explores the use of three modeling approaches: Poisson regression of counts of genetic effects per cell; dynamic modeling of the time-course of micronucleus production and loss as a function of exposure; and categorical regression of sets of genetic toxicity experiments, the results of which are recoded in terms of severities of response. Estimates derived from these models (benchmark doses and predictions of response rates for predetermined doses of interest) are then used to assess the relevance and role of the genetic toxicity results in a risk assessment. With respect to the acrylamide data base, the results suggest that the genetic damage studies do not appear to be consistent or congruent with the thyroid tumor endpoints observed in two long-term bioassays in rats. This suggests that acrylamide's mechanism of action with respect to production of such tumors may not be genotoxic, and that a cancer risk assessment that applied a linear, no-threshold approach to such endpoints might be inappropriate. Benchmark doses derived from the genetic toxicity data base do not appear to be the critical ones for acrylamide risk assessment. Dose metric and modeling issues associated with the proposed dose-response approach to evaluation of genetic toxicity data are explored, and it is recommended that further advancements of the methodology be developed and employed for optimal use of such data for risk assessment purposes.

Comparison of acrylamide metabolism in humans and rodents.

Acrylamide is metabolized by direct conjugation with glutathione or oxidation to glycidamide, which undergo further metabolism and are excreted in urine. In rats administered 3 mg/kg 1,2,3-13C3 acrylamide, 59% of the metabolites excreted in urine was from acrylamide-glutathione conjugation, whereas 25% and 16% were from two glycidamide-derived mercapturic acids. Glycidamide and dihydroxypropionamide were not detected at this dose level. The metabolism of acrylamide in humans was investigated in a controlled study with IRB approval, in which sterile male volunteers were administered 3 mg/kg 1,2,3-13C3 acrylamide orally. Urine was collected for 24 h after administration, and metabolites were analyzed by 13C NMR spectroscopy. At 24 h, urine contained 34% of the administered dose, and 75% of the metabolites were derived from direct conjugation of acrylamide with glautathione. Gycidamide, dihydroxypropionamide and one unidentified metabolite were also detected in urine. This study indicated differences in the metabolism of acrylamide between humans and rodents.

Metabolism and hemoglobin adduct formation of acrylamide in humans.

Acrylamide (AM), used in the manufacture of polyacrylamide and grouting agents, is produced during the cooking of foods. Workplace exposure to AM can occur through the dermal and inhalation routes. The objectives of this study were to evaluate the metabolism of AM in humans following oral administration, to compare hemoglobin adduct formation on oral and dermal administration, and to measure hormone levels. The health of the people exposed under controlled conditions was continually monitored. Prior to conducting exposures in humans, a low-dose study was conducted in rats administered 3 mg/kg (1,2,3-13C3) AM by gavage. The study protocol was reviewed and approved by Institute Review Boards both at RTI, which performed the sample analysis, and the clinical research center conducting the study. (1,2,3-13C3) AM was administered in an aqueous solution orally (single dose of 0.5, 1.0, or 3.0 mg/kg) or dermally (three daily doses of 3.0 mg/kg) to sterile male volunteers. Urine samples (3 mg/kg oral dose) were analyzed for AM metabolites using 13C NMR spectroscopy. Approximately 86% of the urinary metabolites were derived from GSH conjugation and excreted as N-acetyl-S-(3-amino-3-oxopropyl)cysteine and its S-oxide. Glycidamide, glyceramide, and low levels of N-acetyl-S-(3-amino-2-hydroxy-3-oxopropyl)cysteine were detected in urine. On oral administration, a linear dose response was observed for N-(2-carbamoylethyl)valine (AAVal) and N-(2-carbamoyl-2-hydroxyethyl)valine (GAVal) in hemoglobin. Dermal administration resulted in lower levels of AAVal and GAVal. This study indicated that humans metabolize AM via glycidamide to a lesser extent than rodents, and dermal uptake was approximately 6.6% of that observed with oral uptake.

Epidemiologic evidence for assessing the carcinogenicity of acrylamide.

Acrylamide (ACM) has recently been found in fried and baked foods, suggesting widespread public exposure. ACM is an industrial chemical that causes neurotoxicity in humans and an increase in benign tumors of the endocrine system of laboratory rats. The U.S. EPA and the International Agency for Research on Cancer (IARC) have designated ACM as a probable human carcinogen based on the bioassay data and evidence for a DNA reactive mechanism. We report here an assessment of the published epidemiological data with regard to exposure to ACM. The results of an epidemiology mortality study of heavily exposed workers published in 1999 failed to reveal any increase in total cancer in this workforce. The average total exposure in the exposed group was equivalent to over 100% of the estimated average lifetime dietary intake, assuming a U.S. diet. However, this epidemiologic information had limited power to detect modest increases in specific tumors of the type reported in the rodent studies. Although the mortality study could not have picked up the small increases in cancer or in specific cancer types predicted by EPA's linear extrapolation model, research on biochemical and physiological mechanisms suggests that EPA's assessment overstates the potency, and therefore, the risk from foods and other sources of exposure may be lower than previously anticipated.

The acute effects of acrylamide on astrocyte functions.

We assessed biochemical endpoints indicative of acute toxicity in neonatal rat primary astrocyte cultures exposed to acrylamide. Metallothionein (MT), glutamine synthetase (GS), glutamate/aspartate transporter (GLAST), and taurine transporter (tau-T) mRNA expression levels as well as cell volume were determined in astrocytes acutely treated with 0.1 and 1.0 mM acrylamide. Statistically significant changes in acrylamide treated astrocytes were noted for GS (0.1 mM) and GLAST (1.0 mM) mRNA expression levels. All other measurements were insignificant in comparison with controls, suggesting that astrocytic function is minimally compromised even at exceedingly high levels of acute acrylamide exposure.

Effects of acrylamide on rodent reproductive performance.

Acrylamide monomer causes peripheral neurotoxicity, mutagenicity, clastogenicity, male reproductive toxicity, prenatal lethality, and endocrine-related tumors in rodents. Acrylamide (and/or its metabolite glycidamide) binds to dopamine receptors and spermatid protamines and inhibits activity of kinesin and dyneine, resulting in interference with neuronal intracellular transport and sperm motility. Glycidamide binds to various proteins and DNA. Acrylamide at low doses decreases litter size, with rats more sensitive than mice. At higher doses, sperm morphology and motility and neurotoxicity are affected, which decreases mating frequency. Acrylamide does not affect female reproduction (females exhibit neurotoxicity). Dominant lethal mutations cause decreased newborn litter size. The mechanisms of action appear to be: (1) acrylamide/glycidamide binding to spermatid protamines, causing dominant lethality and effects on sperm morphology; and (2) acrylamide binding to motor proteins, causing distal axonopathy, including hindlimb weakness/paresis, and effects on mounting, sperm motility, and intromission. Glycidamide-induced mutations appear to play no role in reproductive or neurologic toxicity.