Short communication Altered hepatic retinol and CYP26 levels in adult European common frogs (Rana temporaria) exposed to p,p 0 -DDE A ` ngels Leiva-Presa * , Anne Skjetne Mortensen, Augustine Arukwe, Bjørn Munro Jenssen Department of Biology, Norwegian University of Science and Technology, N-7491 Trondheim, Norway Abstract The effects of environmental contamination on amphibians are of particular concern because there are reports of declining numbers of species and individuals in most parts of the world during the last 50 years. During the last decade there has been increased focus on the role of persistent organic pollutants as retinoid (vitamin A) disrupters, and their effects on development, growth and sexual differentiation. To study the effects of p,p 0 -DDE, one of the most persistent metabolites of the pesticide DDT, on retinol homeostasis, we subcutaneously exposed adult male European com- mon frogs (Rana temporaria) to different doses of p,p 0 -DDE (0, 0.01, 0.1, 1 and 10 mg/kg body mass) and studied the effect of a short term exposure (14 days) on hepatic retinoid levels and CYP26 gene and protein expression. Hepatic retinol concentrations, CYP26 gene and protein levels were analysed using HPLC, quantitative RT-PCR and indirect ELISA, respectively. Our results showed a signifi- cant p,p 0 -DDE dose-specific increase in the hepatic retinol concentration. CYP26 gene and protein expression were reduced in an apparent p,p 0 -DDE dose-specific manner. The results suggest that p,p 0 -DDE may interfere with the hepatic metabolism of retinol in adult frogs by decreasing CYP26 expression patterns. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Amphibians; Endocrine disruption; Rana temporaria; Organochlorine pesticides; p,p 0 -DDE; Reti- noids; CYP26 0141-1136/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.marenvres.2006.04.013 * Corresponding author. Tel.: +34 606 800 119; fax: +47 735 91309. E-mail address: angels_leiva_presa@yahoo.es (A ` . Leiva-Presa). Marine Environmental Research 62 (2006) S10–S15 www.elsevier.com/locate/marenvrev MARINE ENVIRONMENTAL RESEARCH