title: Postmetamorphic Xenopus laevis shows decreased plasma triiodothyronine concentrations and phosphorylase activity due to subacute phytosterol exposure.
abstract: Postmetamorphic South African clawed frogs (Xenopus laevis) were exposed to a phytosterol mixture (ca. 80% beta-sitosterol and less sitostanol, campesterol, and campestanol) for 14 days at 30 mugl(-1) in a flow-through system. The effects of phytosterols (PS) on the plasma thyroid hormone (T(3) and T(4)), testosterone, leptin-immunoreactive peptide and tissue glycogen concentrations were determined. The following enzyme activities were also analyzed from the liver and muscle: glycogen phosphorylase and lipase, and from the liver only: glucose-6-phosphatase. The plasma T(3) concentration was lower in the PS-exposed female frogs. Both muscle lipase and glycogen phosphorylase activities were also lower in the PS-exposed animals. These results could indicate that the basal metabolic rate and locomotion activity of the frogs were decreased. The effects could not be attributed to the possible estrogenicity of the PS mixture. Further studies will be needed to evaluate the possible significance of these effects.
authors.affiliation: Department of Biology, University of Joensuu, P.O. Box 111, FIN-80101 Joensuu, Finland. petri.koponen@joensuu.fi
authors.forename: Petri S
authors.initials: PS
authors.lastname: Koponen
authors.forename: Petteri
authors.initials: P
authors.lastname: Nieminen
authors.forename: Anne-Mari
authors.initials: AM
authors.lastname: Mustonen
authors.forename: Jussi V K
authors.initials: JV
authors.lastname: Kukkonen
mesh_terms: D000818:Animals; D005260:Female; D006003:Glycogen / Q000378:metabolism; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000201:enzymology; D006005:Phosphorylases / Q000378:metabolism*; D010840:Phytosterols / Q000633:toxicity*; D013739:Testosterone / Q000097:blood; D013963:Thyroid Hormones / Q000097:blood; D014284:Triiodothyronine / Q000097:blood*; D014982:Xenopus laevis / Q000097:blood / Q000378:metabolism*
chemical_list: D010840:Phytosterols; D013963:Thyroid Hormones; D014284:Triiodothyronine; D013739:Testosterone; D006003:Glycogen; D006005:Phosphorylases