The effects of the xenoestrogen, octylphenol (OP), and UV-B radiation on somatic development and hypothalamic gene expression of the leopard frog (Rana pipiens).

Abstract

Statistical meta-analysis of large and diverse data sets has indicated that amphibians have been declining worldwide since the 1960s. Exposure to UV-B radiation and endocrine-disrupting chemicals (EDCs) have been considered as possible hypotheses to explain the observed declines. Newly-hatched leopard frog (Rana pipiens) tadpoles were exposed for ten days to one of three concentrations of octylphenol (OP) (10 muM, 1 muM, 1 nM) plus a 0.01% ethanol vehicle control, with and without two levels (7 muW/cm 2, 25 muW/cm2) of UV-B radiation. The LC50 for water borne OP was also determined. OP is an EDC which has been shown to elicit responses similar to 17 beta-estradiol (E2). The RNA-arbitrarily pruned PCR (RAP-PCR) differential display strategy was employed to isolate candidate genes differentially regulated in the tadpole diencephalon which were affected by various OP and UV-B treatments. A reverse Northern multiple-gene dot blot was used to verify expression patterns of specific cDNA transcripts cloned from differential display. Homology cloning was performed to obtain R. pipiens GAD65 and GAD67, enzymes responsible for gamma-aminobutyric acid (GABA) synthesis, and these were included on the dot blot. (Abstract shortened by UMI.)