Meeting Abstract
P3.26 Sunday, Jan. 6 PCB-126 exposure lowered antimicrobial peptide secretion in juvenile northern leopard frogs CARY, TL*; PASK, JD; ROLLINS-SMITH, LA; KARASOV, WH; Univ. of Wisconsin, Madison, WI; Vanderbilt Univ. Medical Center, Nashville, TN; Vanderbilt Univ. Medical Center, Nashville, TN; Univ. of Wisconsin, Madison, WI tcary@wisc.edu
Two factors threatening global amphibian populations are disease and environmental contamination. Chytridiomycosis is an amphibian disease caused by the fungus Batrachochytrium dendrobatidis (Bd); antimicrobial peptides (AMPs) secreted onto the skin of amphibians are thought to defend against Bd, providing a first-line innate immune strategy. We hypothesized that larval exposure to PCB-126, an organic contaminant, would decrease AMPs secreted by post-metamorphic Lithobates pipiens. Tadpoles were fed a control diet or a diet with 0.37, 1.2, or 5.0 ng PCB-126/g until metamorphosis. Juvenile frogs were injected with saline or norepinephrine-HCl dissolved in saline and placed in buffer to collect secreted skin peptides. The peptides were enriched to obtain hydrophobic peptides which include the AMPs and quantified using a bradykinin based peptide assay. Skin peptides were also analyzed using matrix-assisted laser desorption time-of-flight mass spectrometry. Control frogs secreted 593 ±101 µg/g body weight (BW) skin peptides, while frogs exposed to 0.37, 1.2, or 5.0 ng PCB-126/g had 336 ±43, 378 ±62, and 365 ±56 µg/g BW skin peptides, respectively. One-way ANOVA determined no significant difference (p= 0.077), however, post-hoc Dunnet’s test determined that 0.37 ng PCB/g signficantly lowered skin peptide secretion (p= 0.047). Furthermore, when the control group was compared against all PCB-treated animals, PCB-126 significantly lowered skin peptide secretion (p= 0.004). In all treatment groups the suite of AMPs secreted by frogs was similar, indicating that AMP type was not affected by PCB exposure. If a minimum threshold of AMPs is needed to be protective, lowered AMP levels due to contaminant exposure may increase frog susceptibility to Bd.
