Activity patterns of biotransformation enzymes in juvenile chickens after in ovo dosage of PCB126

Characterisation of UDP-glucuronosyltransferase activity in sea turtle Chelonia mydas

Uridine diphosphate glucuronosyltransferase (UGT) enzymes conjugate many lipophilic chemicals, such as drugs, environmental contaminants, and endogenous compounds, promoting their excretion. The complexity of UGT kinetics, and the location of enzyme active site in endoplasmic reticulum lumen, requires an accurate optimisation of enzyme assays.In the present study, we characterised UGT activity in liver microsomes of green turtles (Chelonia mydas), an endangered species. The conditions for measuring UGT activity were standardised through spectrofluorimetric methods, using the substrates 4-methylumbelliferone (4-MU) and uridine diphosphate glucuronic acid (UDPGA) at 30 °C and pH 7.4.The green turtles showed UGT activity at the saturating concentrations of substrates of 250 µM to 4-MU and 7 mM to UDPGA. The alamethicin, Brij^®58, bovine serum albumin (BSA), and magnesium increased UGT activity. The assay using alamethicin (22 µg per mg of protein), magnesium (1 mM), and BSA (0.25%) reached the highest V_max (1203 pmol·min^-1mg·protein^-1). Lithocholic acid and diclofenac inhibited UGT activity in green turtles.This study is the first report of UGT activity in the liver of green turtles and provides a base for future studies to understand the mechanisms of toxicity by exposure to contaminants in this charismatic species.

Expression of advanced glycation end-products and NFκB in chick embryos exposed to dioxins and treated with acetylsalicylic acid and α-tocopherol

Dioxins have adverse and multifaceted effect on body functions. They are known to be carcinogens, immunotoxins, and teratogenic agents. In vivo, transformation of dioxins occurs after their interaction with the aryl hydrocarbon receptor (AhR) and leads to formation of proinflammatory and toxic metabolites. The aim of this study was to verify whether α-tocopherol (vitamin E) and acetylsalicylic acid (ASA), could reduce the damage caused by the action of dioxins. Fertile chicken eggs were injected with a solution of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), followed by the injection of α-tocopherol or acetylsalicylic acid. Organs such as heart and liver were dissected from the chick embryos at d 13 and 19 of development and subjected to immunohistochemical analysis of presence of advanced glycation end products (AGEs) and nuclear factor kappa B (NFκB) in tissues. The AGEs were used as the marker for exposure to dioxins, since it is well established that their level increases in dioxin-damaged tissues. Formation of AGEs was evaluated in embryos exposed to dioxin and treated with vitamin E and/or ASA (against dioxin-exposed, untreated controls). We have found that TCDD causes developmental disorders and increases the level of AGEs in chick embryo tissues. The use of such pharmacological agents as vitamin E, ASA, and combination of ASA and vitamin E, inhibited formation of the AGEs in 13-day-old embryos and reduced the AGEs level in embryos after 19 d of the development.

Updated perspectives on the cytosolic sulfotransferases (SULTs) and SULT-mediated sulfation

The cytosolic sulfotransferases (SULTs) are Phase II detoxifying enzymes that mediate the sulfate conjugation of numerous xenobiotic molecules. While the research on the SULTs has lagged behind the research on Phase I cytochrome P-450 enzymes and other Phase II conjugating enzymes, it has gained more momentum in recent years. This review aims to summarize information obtained in several fronts of the research on the SULTs, including the range of the SULTs in different life forms, concerted actions of the SULTs and other Phase II enzymes, insights into the structure-function relationships of the SULTs, regulation of SULT expression and activity, developmental expression of SULTs, as well as the use of a zebrafish model for studying the developmental pharmacology/toxicology.