Monster Seminar Jam - Dissecting Multiple
Dr. Glen Van Der Kraak, College of Biological Science, University of Guelph
The concept that chemicals found in the environment may alter the normal functioning of the endocrine system and consequently cause adverse health effects in humans or wildlife has emerged as one of the major issues in environmental toxicology today. One such example is the altered sex steroid secretion and reproductive abnormalities including reduced ovarian size, delayed sexual maturity, and increased ovarian follicle cell apoptosis which are observed in fish collected downstream of bleached kraft pulp and paper mills in Canada. While there may be many factors that could contribute to these responses, our use of the epidemiological criteria set out in the Global Assessment of the State of the Science of Endocrine Disruptors (International Program on Chemical Safety, World Health Organization) provides evidence that pulp and paper mill effluent functions as an endocrine disruptor. Identification of the active constituents with the pulp mill effluent contributing to endocrine dysfunction has been challenging. This has been hindered in part by the hundreds of known compounds and many more unidentified compounds that are present in pulp mill effluents. Our work has demonstrated that pulp mill effluent contains ligands for a number of receptors (e.g. aryl hydrocarbon receptor, estrogen, androgen and retinoic acid and retinoid X receptors). Our work has shown that ligands for each of these receptors are rapidly accumulated by fish following exposure to pulp mill effluent and these ligands are rapidly depurated when the fish are returned to clean water. We also constituently observe that fish exposed to pulp mill effluents exhibit elevated levels of thiobarbituric acid (TBARS) and lipid hydroperoxides (LOOH), which are indicators of oxidative stress-induced lipid peroxidation. Pulp mill effluent exposed fish exhibit increased hepatic fatty acyl CoA oxidase activity, which is a peroxisomal enzyme that generates the reactive oxygen species (ROS) hydrogen peroxide. Collectively these studies provide evidence that pulp mill effluent contain multiple chemicals that affect endocrine physiology and that these may act via multiple pathways to affect reproductive function.
Date and Time:
January 20, 2005,
11:00 am - 12:30 pm