Toxicokinetics of the broad-spectrum pyrethroid insecticide deltamethrin in broiler chickens

A generic avian physiologically-based kinetic (PBK) model and its application in three bird species

Physiologically-based kinetic (PBK) models are effective tools for designing toxicological studies and conducting extrapolations to inform hazard characterization in risk assessment by filling data gaps and defining safe levels of chemicals. In the present work, a generic avian PBK model for male and female birds was developed using PK-Sim and MoBi from the Open Systems Pharmacology Suite (OSPS). The PBK model includes an ovulation model (egg development) to predict concentrations of chemicals in eggs from dietary exposure. The model was parametrized for chicken (Gallus gallus), bobwhite quail (Colinus virginianus) and mallard duck (Anas platyrhynchos) and was tested with nine chemicals for which in vivo studies were available. Time-concentration profiles of chemicals reaching tissues and egg compartment were simulated and compared to in vivo data. The overall accuracy of the PBK model predictions across the analyzed chemicals was good. Model simulations were found to be in the range of 22-79% within a 3-fold and 41-89% were within 10- fold deviation of the in vivo observed data. However, for some compounds scarcity of in-vivo data and inconsistencies between published studies allowed only a limited goodness of fit evaluation. The generic avian PBK model was developed following a "best practice" workflow describing how to build a PBK model for novel species. The credibility and reproducibility of the avian PBK models were scored by evaluation according to the available guidance documents from WHO (2010), and OECD (2021), to increase applicability, confidence and acceptance of these in silico models in chemical risk assessment.

Toxicokinetic of cyphenothrin in rabbits

Type II pyrethroids, including cyphenothrin, have a wider efficacy and spectrum of action because they have a killing effect rather than a knockdown effect on pests. For this reason, they are among the most widely used pyrethroid groups today. In addition, this group also has repellent activity. Thus, cyphenothrin is a commonly used pyrethroid, which poses an exposure/toxicity risk for living organisms. Toxicokinetic studies have an important place in predicting the toxicity risks of compounds and evaluating viable treatment options. In this study, the toxicokinetics of cyphenothrin were investigated in rabbits. The animal material of the study comprised 6-month-old female 14 New Zealand rabbits, each weighing 2-2.5 kg. The animals were randomly assigned to two groups, each of 7 animals. The rabbits in group 1 were administered a single dose of 2.5 mg/kg bw cyphenothrin in dimethyl sulfoxide as an intravenous bolus, while the rabbits in group 2 were administered a single dose of 2.5 mg/kg bw cyphenothrin in the same vehicle as an oral bolus. Following the administration of cyphenothrin, blood samples were taken at certain intervals from the auricular vein into heparinized tubes. Plasma cyphenothrin levels were determined by gas chromatography, using a capillary column and a micro-electron capture detector. For orally administered cyphenothrin, the plasma maximum concentration (Cmax), time to reach the maximum value (tmax), half-life (t1/2β), mean residence time (MRT), area under the curve (AUC0→∞), and bioavailability (F) values were determined as 172.28 ± 47.30 ng/ml, 1.07 ± 0.42 h, 12.95 ± 1.11 h, 17.79 ± 1.69 h, 2220.07 ± 572.02 ng/h/ml, and 29.50%, respectively. For intravenous cyphenothrin, the t1/2β, MRT and AUC0→∞ values were ascertained as 7.66 ± 0.74 h, 9.28 ± 0.62 h, and 7524.31 ± 2988.44 ng/h/ml, respectively. Although the bioavailability of cyphenothrin was limited when taken orally, its half-life and mean residence time in the body were found to be long. This suggests that high doses of this pesticide may pose a poisoning risk.

Acute toxicity and metabolism of pesticides in birds

The median lethal dose of pesticide in acute oral toxicity, used as a conservative index in avian risk assessment, varies by the species with differences of less than one order of magnitude, depending on body size, feeding habit, and metabolic enzyme activity. The profiles of pesticide metabolism in birds with characteristic conjugations are basically common to those in mammals, but less information is available on their relevant enzymes. The higher toxicity of some pesticides in birds than in mammals is due to the lower activity of avian metabolic enzymes. The bioaccumulation in birds is limited for very hydrophobic pesticides resistant to metabolic degradation. Several in silico approaches using the descriptors of a pesticide molecule have recently been employed to estimate the profiles of acute oral toxicity and bioaccumulation.

An open source physiologically based kinetic model for the chicken (Gallus gallus domesticus): Calibration and validation for the prediction residues in tissues and eggs

Xenobiotics from anthropogenic and natural origin enter animal feed and human food as regulated compounds, environmental contaminants or as part of components of the diet. After dietary exposure, a chemical is absorbed and distributed systematically to a range of organs and tissues, metabolised, and excreted. Physiologically based kinetic (PBK) models have been developed to estimate internal concentrations from external doses. In this study, a generic multi-compartment PBK model was developed for chicken. The PBK model was implemented for seven compounds (with log K_ow range -1.37-6.2) to quantitatively link external dose and internal dose for risk assessment of chemicals. Global sensitivity analysis was performed for a hydrophilic and a lipophilic compound to identify the most sensitive parameters in the PBK model. Model predictions were compared to measured data according to dataset-specific exposure scenarios. Globally, 71% of the model predictions were within a 3-fold change of the measured data for chicken and only 7% of the PBK predictions were outside a 10-fold change. While most model input parameters still rely on in vivo experiments, in vitro data were also used as model input to predict internal concentration of the coccidiostat monensin. Future developments of generic PBK models in chicken and other species of relevance to animal health risk assessment are discussed.

Acute and single repeated dose effects of low concentrations of chlorpyrifos, diuron, and their combination on chicken

This study investigated the acute and single repeated dose effects of low concentrations of chlorpyrifos, diuron, and their mixture to chicken. The effects were determined as biological response (chicken behavior); physiological response (body weight, gaining weight); and biochemical response such as reduction of acetylcholine esterase activity (ACHE), changes in liver biomarkers, such as (1) alkaline phosphatase (ALP), (2) aspartate aminotransferase (AST), and (3) alanine aminotransferase (ALP), and effects on kidney biomarkers such as total protein, creatinine, uric acid, and urea. Results showed abnormal behavior on chicken received 5 μg/g and above from the tested compounds. A reduction in growth weight was observed in chicken received a single repeated dose of diuron and mixture. Enlargements in the liver and heart were observed in chicken received a single repeated dose of diuron. Percentage of serum ACHE inhibition increased linearly as the concentration of the tested compounds increased. The tested low concentration showed tremendous effects on liver enzymes and kidney functions. Similarly, a single repeated dose of the tested compounds caused severe inhibition on serum ACHE and affected the liver enzyme activities and kidney functions. It can be concluded that the low concentrations are not safe and may cause severe damage to the liver, heart, or kidney and disturb the life.