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EVALUATION OF ENDOGENOUS HORMONES AND A XENOBIOTIC PESTICIDE ON SHEEPSHEAD MINNOW GROWTH USING MOLECULAR BIOLOGICAL TECHNIQUES
Knoebl, I., L. D. Gillis, AND L C. Folmar. EVALUATION OF ENDOGENOUS HORMONES AND A XENOBIOTIC PESTICIDE ON SHEEPSHEAD MINNOW GROWTH USING MOLECULAR BIOLOGICAL TECHNIQUES. Presented at American Fisheries Society Meeting, Phoenix, AZ, Aug. 19-23, 2001.
Presented at the 131st Annual Meeting of the American Fisheries Society, "2001: A Fisheries Odyssey: The Journey of Science and Education Continues," 19-23 August 2001, Phoenix, AZ. 1 p.
We have developed a teleost model to screen physiological effects of endocrine disrupting chemicals (EDCs) on somatic growth. Growth is largely controlled by the endocrine system via the growth-hormone releasing hormone (GRF) - growth hormone (GH) - insulin-like growth factor (IGF) axis (Figure 1). We used two techniques to study the axis, quantitative real-time PCR (TaqMan) and diferential display analysis.
We conducted an 18-week aquatic exposure of newly hatched sheepshead minnows (Cyprinodon variegatus) to E2 (which has been attributed to both enhance and inhibit growth) and chlorpyrifos (an organophosphate insecticide known to inhibit growth in fish). The fish were exposed to two concentrations of E2 (20 and 100ng/L) and to three concentrations (12.5, 25 and 50 ug/L) of chlorpyrifos. While E2 did not affect growth, fish exposed to the highest dose of chlorpyrifos had significantly reduced growth rates (P < 0.05) compared to controls. Hepatic IGF-I mRNA levels were measured using TaqMan technology. While IGF-I mRNA levels were not significantly lower in the E2 exposed fish, there was less variation in the measured amount.
To establish patterns of gene up- or down-regulation, differential display analysis was performed on livers of fish exposed to the highest doses of E2 and chlorpyrifos, as well as fish injected with 10 ?g/g body weight (BW) GH and 1.0 ?g/g BW thyroid hormone (T3).