Oral Gavage Study Research Articles

Gastrointestinal Incomplete Degradation Exacerbates Neurotoxic Effects of PLA Microplastics via Oligomer Nanoplastics Formation.

Biodegradable plastics, hailed for their environmental friendliness, may pose unforeseen risks as they undergo gastrointestinal degradation, forming oligomer nanoplastics. Despite this, the influence of gastrointestinal degradation on the potential human toxicity of biodegradable plastics remains poorly understood. To this end, the impact of the murine in vivo digestive system is investigated on the biotransformation, biodistribution, and toxicity of PLA polymer and PLA oligomer MPs. Through a 28-day repeated oral gavage study in mice, it is revealed that PLA polymer and oligomer microplastics undergo incomplete and complete degradation, respectively, in the gastrointestinal tract. Incompletely degraded PLA polymer microplastics transform into oligomer nanoplastics, heightening bioavailability and toxicity, thereby exacerbating overall toxic effects. Conversely, complete degradation of PLA oligomer microplastics reduces bioavailability and mitigates toxicity, offering a potential avenue for toxicity reduction. Additionally, the study illuminates shared targets and toxicity mechanisms in Parkinson's disease-like neurotoxicity induced by both PLA polymer and PLA oligomer microplastics. This involves the upregulation of MICU3 in midbrains, leading to neuronal mitochondrial calcium overload. Notably, neurotoxicity is mitigated by inhibiting mitochondrial calcium influx with MCU-i4 or facilitating mitochondrial calcium efflux with DBcAMP in mice. These findings enhance the understanding of the toxicological implications of biodegradable microplastics on human health.

Utility of in vivo metabolomics to support read-across for UVCB substances under REACH.

Structure-based grouping of chemicals for targeted testing and read-across is an efficient way to reduce resources and animal usage. For substances of unknown or variable composition, complex reaction products, or biological materials (UVCBs), structure-based grouping is virtually impossible. Biology-based approaches such as metabolomics could provide a solution. Here, 15 steam-cracked distillates, registered in the EU through the Lower Olefins Aromatics Reach Consortium (LOA), as well as six of the major substance constituents, were tested in a 14-day rat oral gavage study, in line with the fundamental elements of the OECD 407 guideline, in combination with plasma metabolomics. Beyond signs of clinical toxicity, reduced body weight (gain), and food consumption, pathological investigations demonstrated the liver, thyroid, kidneys (males only), and hematological system to be the target organs. These targets were confirmed by metabolome pattern recognition, with no additional targets being identified. While classical toxicological parameters did not allow for a clear distinction between the substances, univariate and multivariate statistical analysis of the respective metabolomes allowed for the identification of several subclusters of biologically most similar substances. These groups were partly associated with the dominant (> 50%) constituents of these UVCBs, i.e., indene and dicyclopentadiene. Despite minor differences in clustering results based on the two statistical analyses, a proposal can be made for the grouping of these UVCBs. Both analyses correctly clustered the chemically most similar compounds, increasing the confidence that this biological approach may provide a solution for the grouping of UVCBs.

Gut microbiome and plasma metabolome changes in rats after oral gavage of nanoparticles: sensitive indicators of possible adverse health effects

BackgroundThe oral uptake of nanoparticles is an important route of human exposure and requires solid models for hazard assessment. While the systemic availability is generally low, ingestion may not only affect gastrointestinal tissues but also intestinal microbes. The gut microbiota contributes essentially to human health, whereas gut microbial dysbiosis is known to promote several intestinal and extra-intestinal diseases. Gut microbiota-derived metabolites, which are found in the blood stream, serve as key molecular mediators of host metabolism and immunity.ResultsGut microbiota and the plasma metabolome were analyzed in male Wistar rats receiving either SiO2 (1000 mg/kg body weight/day) or Ag nanoparticles (100 mg/kg body weight/day) during a 28-day oral gavage study. Comprehensive clinical, histopathological and hematological examinations showed no signs of nanoparticle-induced toxicity. In contrast, the gut microbiota was affected by both nanoparticles, with significant alterations at all analyzed taxonomical levels. Treatments with each of the nanoparticles led to an increased abundance of Prevotellaceae, a family with gut species known to be correlated with intestinal inflammation. Only in Ag nanoparticle-exposed animals, Akkermansia, a genus known for its protective impact on the intestinal barrier was depleted to hardly detectable levels. In SiO2 nanoparticles-treated animals, several genera were significantly reduced, including probiotics such as Enterococcus. From the analysis of 231 plasma metabolites, we found 18 metabolites to be significantly altered in Ag-or SiO2 nanoparticles-treated rats. For most of these metabolites, an association with gut microbiota has been reported previously. Strikingly, both nanoparticle-treatments led to a significant reduction of gut microbiota-derived indole-3-acetic acid in plasma. This ligand of the arylhydrocarbon receptor is critical for regulating immunity, stem cell maintenance, cellular differentiation and xenobiotic-metabolizing enzymes.ConclusionsThe combined profiling of intestinal microbiome and plasma metabolome may serve as an early and sensitive indicator of gut microbiome changes induced by orally administered nanoparticles; this will help to recognize potential adverse effects of these changes to the host.

Application of open-source PBPK models in rat-to-human pharmacokinetic extrapolation of oral nicotine exposure

Physiologically Based Pharmacokinetic (PBPK) models are often developed using animal data and applied to predict chemical movement and concentration in humans. However, differences in physiology and exposure routes between animal experiments and human exposures may impact the predictions and interpretation of PBPK model results. Data are needed to parameterize PBPK models, potentially requiring chemical-specific adjustment to model inputs. Since data may be limited for a chemical or exposure of interest, in silico approaches such as chemical structure-based modeling can help fill the gaps. This case study assesses generalized, open-source PBPK models for interspecies kinetic extrapolation of nicotine using both in vivo data from a rat oral gavage study and in silico predictions. Nicotine is used as a data-rich example chemical because PK data are available from different exposure routes in both humans and animals. Rat nicotine plasma data were obtained after oral gavage dosing of nicotine (up to 8 mg/kg/day over 7 days) and used to develop human nicotine models for both oral ingestion and buccal (mouth tissue) absorption. As an open-source buccal tissue absorption model was not available, we mimicked a buccal exposure by modifying the open-source model for the intravenous exposure route. An 8 mg/kg/day human dose using oral ingestion and buccal absorption resulted in an approximately 2- and 4-fold higher predicted maximum plasma concentration (Cmax) than an 8 mg/kg/day gavage exposure in rats, respectively, highlighting the impact of species and exposure route on model predictions. This study demonstrates that a generalized and open-source PBPK model can extrapolate the plasma kinetic profiles of nicotine between species using in vivo and in silico data after accounting for differences in exposure routes. In silico-informed model parameterizations provided similar results to rat in vivo-based parameterizations, highlighting the potential use of in silico approaches when data are limited.

Transcriptomics analysis of hepatotoxicity induced by the pesticides imazalil, thiacloprid and clothianidin alone or in binary mixtures in a 28-day study in female Wistar rats

Co-occurrence of pesticide residues in food commodities raises a potential safety issue as their mixture effects on human health are largely unknown. In a previous study, we reported the toxicological effects (pathology and histopathology) of imazalil (IMZ), thiacloprid (THI), and clothianidin (CTD) alone and in binary mixtures in a 28-day oral gavage study in female Wistar rats. Five dose levels (up to 350 mg/kg body weight/day) ranging from a typical toxicological reference value to a clear effect dose were applied. In the present study, we undertook a transcriptomics analysis of rat livers by means of total RNA sequencing (RNA-Seq). Bioinformatic data analysis involving Ingenuity Pathway Analysis (IPA) was used to gain mechanistic information on hepatotoxicity-related pathways affected after treatment with the pesticides, alone and in mixtures. Our data show that 2986 genes were differentially regulated by CTD while IMZ and THI had effects on 194 and 225 genes, respectively. All three individual compounds shared a common subset of genes whose network is associated with xenobiotic metabolism and nuclear receptor activation. Similar networks were retrieved for the mixtures. Alterations in the expression of individual genes were in line with the assumption of dose addition. Our results bring new insight into the hepatotoxicity mechanisms of IMZ, THI, and CTD and their mixtures.

The potential gonadoprotective effects of grape seed extract against the histopathological alterations elicited in an animal model of cadmium-induced testicular toxicity.

Grape seed extract (GSE) is a powerful antioxidant containing high levels of bioflavonoids, vitamin C and vitamin E. The aim of the work is to study the possible protective and ameliorative effects of grape seed extract in an animal model of cadmium (Cd)-induced testicular toxicity in rats. A thirty-day oral gavage study in adult male albino rats was performed using 32 animals, randomly divided into four equal groups; negative control, Cd (5 mg/k/day), GSE (100 mg/k/day), and Cd + GSE. Testicular weights were measured. Haematoxylin and eosin (H&E) staining and proliferating nuclear cell antigen (PCNA) immunohistochemistry, as a marker for proliferation were done. Morphometric parameters were assessed and subjected to statistical analysis. The H&E results showed atrophy and distortion of the seminiferous tubules (STs) with sloughing of the spermatogenic epithelium in cadmium group. The interstitial spaces were widened and showed oedema and mononuclear cell infiltrations. No remarkable changes were observed in the GSE-only group when compared to the control group. In Cd + GSE group, maintaining of the STs and their lining cells was evident. The immunohistochemical results showed marked positive PCNA immunoreactivity in both control and GSE groups, while negative immunoreaction was noticed in Cd group. Limited positive PCNA immunoreactivity was ameliorated in Cd + GSE group. Grape seed extract protected against cadmium-induced testicular toxicity in rats, reducing induced histopathological changes, and maintaining testicular histoarchitecture.

In vitro stability and in vivo pharmacokinetics of the novel ketogenic ester, bis hexanoyl (R)-1,3-butanediol

A novel ketone ester, bis hexanoyl (R)-1,3-butanediol (BH-BD), has been developed as a means to elevate blood ketones, for use as an energy substrate and a signaling metabolite. The metabolism of BH-BD and its effects on blood beta-hydroxybutyrate (BHB) levels was evaluated in various in vitro matrices and through analysis of plasma collected from Sprague Dawley rats and C57/BL6 mice in two oral gavage studies. A well-characterized ketone ester, (R)-3-hydroxybutyl (R)-3-hydroxybutyrate (HB–BHB), was used as an active control throughout. In vitro assay results demonstrated that BH-BD likely remains intact in the stomach and is hydrolyzed in the small intestine into hexanoate and (R)-1,3-butanediol. If absorbed intact, BH-BD is subject to hydrolysis by non-CYP enzymes in liver and esterases in plasma. If BH-BD reaches the lower intestine it is metabolized by gut flora. Plasma BHB delivery increased in a dose-dependent manner in rats and mice following oral administration of BH-BD. All doses of BH-BD were well tolerated. At doses over 3 g/kg, BHB delivery was similar between BH-BD and HB-BHB. The results of these studies support the hydrolysis of BH-BD into hexanoate and (R)-1,3-butanediol which are metabolized into BHB, delivering a well-tolerated, sustained and dose-dependent increase in plasma BHB in rodents.

Genotoxicity and neonatal subchronic toxicity assessment of a novel mixture of the human-identical milk oligosaccharides lacto-N-fucopentaose I and 2'-fucosyllactose.

Human milk oligosaccharides (HMOs) are a complex group of bioactive molecules largely observed in human breast milk but also occurring in limited amounts in other mammalian milks. Advances in biotechnology have enabled production of human-identical milk oligosaccharides (HiMOs), structurally identical molecules to HMOs found naturally in human milk, intended for addition to infant formula to more closely replicate breast milk. Biosynthesis of a novel mixture of two major HMOs, lacto-N-fucopentaose I and 2'-fucosyllactose (LNFP-I/2'-FL), recently became possible. To support the safety of LNFP-I/2'-FL for use in infant formula and other foods, it was subject to a safety assessment comprising a bacterial reverse mutation test, an in vitro mammalian cell micronucleus test, and a 90-day oral gavage study in neonatal rats. In the 90-day study (the first HiMO study to include the new endocrine-sensitive endpoints described in the 2018 version of OECD Test Guideline 408), LNFP-I/2'-FL was administered by oral gavage to neonatal rats once daily (from Day 7 of age) for 90 consecutive days, at doses up to 5000 mg/kg bw/day, followed by a 4-week recovery period. Concurrent reference controls received 5000 mg/kg bw/day of the approved infant formula ingredient oligofructose. LNFP-I/2'-FL was nongenotoxic in vitro. The highest dose tested (5000 mg/kg bw/day) was established as the no-observed-adverse-effect level in the 90-day study, as there were no test article-related adverse effects on clinical observations, body weight, food consumption, clinical pathology, and organ weights nor any noteworthy macroscopic or microscopic findings. This supports the safety of LNFP-I/2'-FL for its intended uses in food.

Sex-specific accumulation of silver nanoparticles in rat kidneys is not ovarian hormone regulated but elimination limited

Preferential Ag deposition in female kidneys has been reported in subacute and subchronic oral gavage and inhalation studies of various sizes of silver nanoparticles (AgNPs). In these in vivo animal studies, female kidneys were shown to accumulate 3–4 times more silver than male kidneys. The current 28-day oral gavage study of AgNPs administered to ovariectomized female rats investigated the effect of sex-dependent hormones. Ovariectomized rats were allowed to recover for 14 days, then AgNPs (60 nm) were administered by gavage for 28 days based on 500 mg/kg body weight. After this subacute oral exposure, the rats were sacrificed and the Ag content in the kidneys was measured using an atomic absorption spectrophotometer. No statistically significant difference was noted in the Ag content in the kidneys among the AgNP administered, AgNP administered sham, and AgNP administered ovariectomized rats, although the female kidneys showed a statistically significant higher accumulation of Ag than the male kidneys. Reanalysis of the clearance of Ag accumulated in the kidneys showed 2 different phases; fast (T1/210.4 days) and slow (T1/2 61.9 days) for males, while the clearance of females showed (T1/2 20.8 days) and slow (T1/2 154 days). The higher accumulation of Ag in female kidneys is due to slower clearance of Ag in female kidneys than those of males. Therefore, the current results indicate that the preferential silver accumulation in female kidneys is not regulated by ovarian hormones, but by elimination rate differences between males and females.

Safety evaluation of collagenase from Streptomyces violaceoruber

A safety assessment was conducted for microbial collagenase (COL) enzyme expressed in Streptomyces violaceoruber. The acute oral toxicity of COL was examined in Sprague-Dawley rats and the LD50 of COL via single oral administration to rats was higher than 2000 mg/kg body weight. A 13-week oral gavage study of COL showed no adverse effects due to the enzyme up to a dose of 234.9 mg total organic solids (TOS)/kg body weight per day (NOAEL). A bacterial reverse mutation test showed no mutagenic activity at the highest dose (4698 μg TOS per plate). In the mouse lymphoma TK assay, a positive result was observed at the highest dose of 4698 μg TOS/mL although it had low reproducibility. To confirm the chromosome aberration potential, an in vivo micronucleus test was conducted that demonstrated the lack of mutagenic potential on the bone marrow of rats at doses up to 1879 mg TOS/kg body weight per day. The results of the genotoxicity studies and acute and subchronic rat studies support the safe use in food production of collagenase produced from S. violaceoruber.

Is there a rationale for direct dosing of chemicals to nursing pups in the EOGRTS (OECD 443)?

In OECD guideline 443 – Extended One Generation Reproductive Toxicity Study (EOGRTS) – to be used for testing industrial and agrochemicals, it has been indicated that careful consideration of benefits and disadvantages should be made prior to conducting direct-dosing studies in nursing pups. Nursing pups will not be directly dosed in dietary and drinking water studies whereas in oral gavage studies this possibility exists. Besides the risk of intubation trauma and overdosing due to direct exposure and exposure via the mother's milk, direct dosing could lead to a different hazard assessment of chemicals depending on the choice of the route of administration. In addition, in case of industrial and agrochemicals used in industrial or professional settings only, there will never be direct exposure of newborns. Moreover, direct dosing of nursing pups is an artificial, non-physiological, route of exposure and as such it would hamper risk assessment. It should therefore only be considered in exceptional cases and justified on a case-by-case approach.

Aluminum and aluminum oxide nanomaterials uptake after oral exposure - a comparative study

The knowledge about a potential in vivo uptake and subsequent toxicological effects of aluminum (Al), especially in the nanoparticulate form, is still limited. This paper focuses on a three day oral gavage study with three different Al species in Sprague Dawley rats. The Al amount was investigated in major organs in order to determine the oral bioavailability and distribution. Al-containing nanoparticles (NMs composed of Al0 and aluminum oxide (Al2O3)) were administered at three different concentrations and soluble aluminum chloride (AlCl3·6H2O) was used as a reference control at one concentration. A microwave assisted acid digestion approach followed by inductively coupled plasma mass spectrometry (ICP-MS) analysis was developed to analyse the Al burden of individual organs. Special attention was paid on how the sample matrix affected the calibration procedure. After 3 days exposure, AlCl3·6H2O treated animals showed high Al levels in liver and intestine, while upon treatment with Al0 NMs significant amounts of Al were detected only in the latter. In contrast, following Al2O3 NMs treatment, Al was detected in all investigated organs with particular high concentrations in the spleen. A rapid absorption and systemic distribution of all three Al forms tested were found after 3-day oral exposure. The identified differences between Al0 and Al2O3 NMs point out that both, particle shape and surface composition could be key factors for Al biodistribution and accumulation.

In Vitro, Ex Vivo and In Vivo Evaluation of Microcontainers for Oral Delivery of Insulin.

Enhancing the oral bioavailability of peptides has received a lot of attention for decades but remains challenging, partly due to low intestinal membrane permeability. Combining a permeation enhancer (PE) with unidirectionally releasing microcontainers (MCs) has previously been shown to increase insulin permeation across Caco-2 cell monolayers. In the present work, this setup was further employed to compare three common PEs—sodium caprate (C10), sodium dodecyl sulfate (SDS), and lauroyl carnitine. The concept was also studied using porcine intestinal tissue with the inclusion of 70 kDa fluorescein isothiocyanate-dextran (FD70) as a pathogen marker. Moreover, a combined proteolysis and Caco-2 cell permeation setup was developed to investigate the effect of soybean trypsin inhibitor (STI) in the MCs. Lastly, in vivo performance of the MCs was tested in an oral gavage study in rats by monitoring blood glucose and insulin absorption. SDS proved to be the most potent PE without increasing the ex vivo uptake of FD70, while the implementation of STI further improved insulin permeation in the combined proteolysis Caco-2 cell setup. However, no insulin absorption in rats was observed upon oral gavage of MCs loaded with insulin, PE and STI. Post-mortem microscopic examination of their gastrointestinal tract indicated lack of intestinal retention and optimal orientation by the MCs, possibly precluding the potential advantage of unidirectional release.

Oral repeated-dose toxicity studies of BIA 10–2474 in CD-1 mice

We independently and retrospectively reviewed three studies that evaluated the toxicity of BIA 10–2474 (3-(1-(cyclohexyl(methyl)carbamoyl)-lH-imidazol-4-yl)pyridine 1-oxide), a novel fatty acid amide hydrolase (FAAH) inhibitor in male and female CD-1 mice based upon raw data obtained from Bial Portela & Companhia S.A. (São Mamede do Coronado, Portugal). These studies were carried out prior to the clinical trial with BIA 10–2474 and formed part of the regulatory submission. An initial oral dose range-finding study with BIA 10–2474 showed that doses from 600 mg/kg/day were poorly tolerated with a high mortality rate and signs of weakness, prostration, labored breathing, clear lacrimation, tachypnea/bradypnea and decreased activity. At lower doses (100 and 300 mg/kg/day) there were few signs but post-mortem analysis showed increased liver weight. In a 28-day study a third of the animals receiving 500 mg/kg/day died or required euthanasia, with similar signs to those seen in the dose-range finding study. At lower doses (i.e. 100 and 300 mg/kg/day) there were few clinical signs although there were dose-related decreases in erythrocyte count and hemoglobin. Histopathology was seen in the 300 and 500 mg/kg/day groups and included hepatocellular hypertrophy (with increased liver weight), nephropathy and enterocyte vacuolation. Finally, in the 13-week oral gavage study, BIA 10–2474 was administered to CD-1 mice of both sexes at dose levels of 25, 75 and 150 mg/kg/day. Under these conditions, there were almost no clinical signs apart from a tendency to increase body-weight. Cholesterol was increased at 75 and 150 mg/kg and remained high after recovery. Liver and spleen weights increased at 75 and 150 mg/kg/day. Histopathologically, there was a dose-dependent increase in sciatic nerve and myofiber degeneration, hepatocellular hypertrophy, nephropathy and inflammatory loci in the bladder. The nerve damage and nephropathy seen at 150 mg/kg/day persisted after a 4-week recovery period. Toxicokinetic analysis in the 4- and 13-week studies showed that exposure was broadly dose-proportional with no evidence of accumulation. On the basis of the changes seen during the 13-week study, the NOAEL was established at 75 mg/kg/day.

Scientific Opinion of Flavouring Group Evaluation 411 (FGE.411): 2-(4-methylphenoxy)-N-(1H-pyrazol-3-yl)-N-(thiophen-2-ylmethyl)acetamide from chemical group 30 (miscellaneous substances).

EFSA was requested to deliver a scientific opinion on the implications for human health of the flavouring substance 2‐(4‐methylphenoxy)‐N‐(1H‐pyrazol‐3‐yl)‐N‐(thiophen‐2‐ylmethyl)acetamide [FL‐no: 16.133], in the Flavouring Group Evaluation 411 (FGE.411), according to Regulation (EC) No 1331/2008 of the European Parliament and of the Council. The substance has not been reported to occur in natural source materials of botanical or animal origin. It is intended to be used as a flavouring substance in specific categories of food but not intended to be used in beverages, except for milk and dairy based beverages that are opaque. The chronic dietary exposure to the substance estimated using the added portions exposure technique (APET), is calculated to be 225 μg/person per day for a 60‐kg adult and 142 μg/person per day for a 15‐kg 3‐year‐old child. A 90‐day oral gavage study in rats showed no adverse effects at doses up to 100 mg/kg body weight (bw) per day, providing an adequate margin of safety. Developmental toxicity was not observed in a study with rats at the dose levels up to 1,000 mg/kg bw per day. The Panel concluded that there is no safety concern for [FL‐no: 16.133], when used as a flavouring substance at the estimated level of dietary exposure calculated using the APET approach and based on the recommended uses and use levels as specified in Appendix B. This conclusion does not apply for use in beverages where the substance can be subject to phototransformation.

Subchronic toxicity of lyophilized apoaequorin protein powder in Sprague-Dawley rats

Apoaequorin is a bioluminescent calcium-binding apoprotein endogenous to the Aequorea species of jellyfish and is commercially available in a dietary supplement in support of brain and cognitive health. Results from a previous 90-day subchronic oral gavage study established the no-observed-adverse-effect-level (NOAEL) of lyophilized apoaequorin protein powder (LAPP) at 666.7 mg/kg/day. The current 90-day oral gavage study in Sprague-Dawley rats administered dose levels of 1000, 2000, and 4000 mg/kg/day of test substance as received. These doses are expressed as milligram of supplement with the amounts of apoaequorin based on the analysis of the percentage of active ingredient. The corresponding amounts of apoaequorin protein are 603, 1206, and 2412 mg/kg/day. These dose levels target approximately 4221, 8442, and 16,844 times more than the expected human oral intake. There were no mortalities, clinical observations, ophthalmological, clinical pathology, or histopathological changes attributable to LAPP administration. Changes in mean body weight and feed efficiency, without other correlating clinical or pathological or other toxicologically relevant findings, were considered to be of little toxicological significance. Therefore, the NOAEL for LAPP administered orally up to 90 days was 4000 mg/kg/day (2412 mg/kg/day based on 603 mg/g or 60.3% active ingredient, apoaequorin protein), the highest dose tested in male and female rats.

Toxicological evaluation of β-Galactosidase enzyme produced by Papiliotrema terrestris

β-Galactosidase (EC 3.2.1.23) is a glycoside hydrolase that catalyzes the release of sugar monomers from β-galactoside oligosaccharides via hydrolysis of glycosidic bonds, and has potential uses in the food industry. The safety of this enzyme and its production organism, Papiliotrema terrestris (P. terrestris), are described herein. P. terrestris was non-pathogenic upon intravenous (IV) administration of 2.4 × 108 cfu and oral administration of 1.3 × 109 cfu. Genotoxic results for the enzyme concentrate were negative in a bacterial reverse mutation test (Ames test) and chromosome aberration test in cultured Chinese hamster lung fibroblast (CHL/IU) cells. In a 13-week oral gavage study in Sprague-Dawley rats, no adverse effects were observed in any of the tested group and a No Observed Adverse Effects Level (NOAEL) of 2000 mg/kg bw/day [total organic solids (TOS) 1800 mg/kg bw/day)] was established, which was the highest dosage tested. Allergenicity sequence analysis revealed no evidence suggesting that β-galactosidase is an allergen. The data presented in this study support the conclusion that β-galactosidase produced from P. terrestris is safe for use in food production.

A physiologically based pharmacokinetic model for the broad-spectrum antimicrobial zinc pyrithione: I. Development and verification

ABSTRACTThe broad-spectrum antimicrobial zinc pyrithione (ZnPT) is used in numerous products ranging from in-can preservative/mildicide in paints to antidandruff shampoo. Although products containing ZnPT have a long history of safe use, regulatory agencies routinely set limits of exposure based upon toxicological considerations. The objective of this study was to create a physiologically based pharmacokinetic (PBPK) model for ZnPT in the rat for improving dose-response analysis of ZnPT-induced toxicity, reversible hindlimb weakness, the endpoint that has been used as the basis for ZnPT risk assessments. A rat oral PBPK model was developed that includes compartments for plasma, liver, kidneys, muscle, brain, and rapidly and slowly perfused tissues. Pyrithione metabolism to 2-(methylsulfonyl)pyridine (MSP) and glucuronide conjugates was incorporated into the model. The model was parameterized and optimized based upon data from single-dose intravenous (iv) and oral gavage pharmacokinetic studies of radiolabeled pyrithione ([14C]PT) administered as zinc [14C]-pyrithione (Zn-[14C]PT) to adult female rats. It was further evaluated and refined using data from repeated, multidose oral gavage and dietary studies of Zn[14C]PT in the adult female rat that included measurements of plasma PT concentration, the putative toxic species. The model replicated the observed short-term elimination kinetics of PT in plasma and [14C]PT in whole blood following single doses and longer term temporal patterns of plasma and blood concentrations during repeated dosing schedules. The model also accounted for production and rapid elimination of S-glucuronide conjugates (SG) of 2-pyridinethiol and 2-pyridinethiol-1-oxide in urine, as well as production and slower elimination of MSP, the major [14C]PT species in blood within several hours following administration of ZnPT. The model provided internal dosimetry predictions for a benchmark dose (BMD) analysis of hindlimb weakness in rats, and was used to combine gavage and dietary studies into a single internal dose-response model with area under the curve (AUC) for plasma PT as the internal dose metric. This PBPK model has predictive validity for calculating internal doses of PT and/or [14C]PT from different routes of exposure in the rat.

Spontaneous and Dosing Route-related Lung Lesions in Beagle Dogs from Oral Gavage and Inhalation Toxicity Studies: Differentiation from Compound-induced Lesions.

This study was conducted to characterize lung microscopic lesions in control beagle dogs from inhalation and oral gavage toxicity studies, to determine differences associated with the route of administration, and to discuss distinguishing features from compound-induced lung lesions. Samples from 138 control dogs from oral gavage studies and 124 control dogs from inhalation (vehicle control) studies were evaluated microscopically. There was no significant sex-related difference in the incidence of all lesions. Perivascular mononuclear cell infiltration, centriacinar mixed cell infiltration, bronchopneumonia, subpleural septal fibrosis, and alveolar macrophage accumulation were the most common lesions. Aspiration pneumonia was more common in dogs from gavage studies, suggesting reflux after gavage dosing or accidental administration of test formulation as possible causes. Centriacinar mixed cell infiltration was more common in dogs from inhalation studies, suggesting mild irritation by the vehicles used. Vascular lesions, which included pulmonary arteriopathy and smooth muscle mineralization, were observed in a few animals. Some of the spontaneous lesions are similar to lesions induced by test compounds. Compared to spontaneous lesions, compound-induced lesions tend to be multifocal or diffuse, follow a pattern of distribution (e.g., centriacinar, perivascular, and interstitial), show a dose response in the incidence and severity, and may show cell-specific toxicity.

Toxicological evaluation of Yulangsan polysaccharide in Wistar rats: A 26-week oral gavage study.

Although numerous studies have proven the medicinal values of Yulangsan polysaccharide (YLSP), the toxicity of this active ingredient is unknown. In the acute toxicity study, a single oral administration of 24 g/kg YLSP caused neither toxicological symptoms nor mortality, and the LD50 was estimated >24 g/kg. In the chronic toxicity study, we administered doses of 0, 0.6, 1.2 and 2.4 g/kg YLSP in rats by oral gavage for 26 weeks followed by a 3-week recovery period. There was no mortality or remarkable clinical signs observed during this 26-week study. Additionally, there were no toxic differences in the following parameters: body weight, food consumption, hematology, clinical biochemistry, organ weight, and macroscopic findings. There were no adverse effects on histopathology observed in males or female rats treated with YLSP. Based on the results, the no-observed-adverse-effect-level of YLSP in rats is greater than 2.4 g/kg when administered orally for 26 consecutive weeks.