PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P579) Effects of Phytosterols on the Post Metamorphic Xenopus laevis.
Koponen, Petri*,1, Nieminen, Petteri1, Anne-Mari, Mustonen1, Kukkonen, Jussi1, 1 University of Joensuu, Joensuu, Finland
ABSTRACT- Phytosterols are present in high concentrations in pulp mill effluents. They are also consumed as natural remedies and margarines by the general population in developed countries to lower elevated serum cholesterol levels. Total number of twenty (11 female, 9 male) post metamorphic Xenopus laevis (African Clawed frog) were exposed to ultrasitosterol (ca. 80% 
-sitosterol, 10% -sitostanol, 9% campesterol and campestanol) concentration of 30 
/L in a flow through system. Temperature in the aquariums was maintained at 20±1°C and light regime was 8/16 (D/L). The aim of this study was to determine the effects of ultrasitosterol on the thyroid hormone (T3 and T4), testosterone and 17-estradiol levels. The following enzyme activities were also analyzed from the liver and muscle: glucose-6-phosphatase, glycogen phosphorylase and lipase esterase. Glycogen concentrations were also determined from both organs. Both controls and solvent controls were included (4 animals per control). After 14 days the frogs were euthanized with MS-222. Blood samples were obtained with a cardiac puncture with sterile needles and syringes into Eppendorf tubes containing EDTA and centrifuged immediately at 1000g. The livers and muscle sample (from right hind limb) were dissected, and frozen in liquid nitrogen. Statistical analyses were performed with Mann-Whitney U test and significance was considered to be significant at p<0.05 level. The results show that this ultrasitosterol concentration does not have any significant effect on hormone levels. During 14 days exposure, however, exposed frogs showed significant differences in muscle lipase esterase, muscle glucose-6-phosphatase, and muscle glycogen phosphorylase concentrations.
Key words: Xenopus laevis, phytosterols, ultrasitosterol