PARENT SESSION
86 - Endocrine Disruption (Fishes)
8:30 AM to 12:20 PM, Thursday, 16 May 2002
Session Chair: Grillitsch, Britta ¹, Schober, Ursula ², ^{1 2} .
Strauss C

(86-04) Thyroid hormones in fish exposed to persistent organic pollutants, from the Yangtze river region, China.

Nugegoda, Dayanthi^*,1, Wenzhong, Wu², Ying, Xu², Zhang, Jie², Henkelmann, Bernhardt³, Schramm, Karl-Werner³, ¹ RMIT University, Melbourne, Australia² Institute of Hydrobiology, Wuhan, China³ Institute of Ecological Chemistry, GSF, Munich, Germany

ABSTRACT- Impaired growth, metabolism and reproduction in fish exposed to persistent organic pollutants in contaminated habitats has been linked to disruption of their endocrine function. Thyroid hormones play a major role in fish metamorphosis, metabolism and growth but there are few studies on the effect of xenobiotics on thyroiid function. Our study investigated thyroid hormones in the chinese silver carp Hypophthalmichthys molitrix sampled from a series of wastewater ponds with a gradient of contamination by polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in the Ya-Er Lake of the Yangtze river region, China. Thyroxine (T4) and triiodothyronine (T3) in fish serum were determined using specific I ¹²⁵ labelled radioimmunoassays. Polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in liver homogenates from samples of the same individuals were quantified using a high resolution mass spectrometer (Finnigan MAT 95S) coupled with a HP GC 6890. T4 and T3 from livers of another series of fish were extracted using barbital buffer and methanol/chloroform separation and measured using I ¹²⁵ labelled radioimmunoassays. Fish from the most contaminated pond had the lowest serum thyroid hormone concentrations. Fish liver samples reflected the bioaccumulation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) corresponding to the gradient in the ponds and T4/T3 concentrations were lower in the liver of silver carp from the more contaminated ponds. Eggs and larvae of the Chinese rare minnow Gobiocypris rarus exposed to a graded series of TCDD concentration in the laboratory had altered thyroid hormone levels compared to controls. Results are discussed in terms of using thyroid hormones in fish as biomarkers of exposure to persistent organic pollutants.

Key words: thyroid hormones, fish, endocrine disruption, dioxin