Physiological effects and tissue residues from exposure of leopard frogs to commercial naphthenic acids.
Naphthenic acids (NAs) have been cited as one of the main causes of the toxicity related to oil sands process-affected materials and have recently been measured in biological tissues (fish). However, adverse effects have not been a consistent finding in toxicology studies on vertebrates. This study set out to determine two factors: 1) whether exposure to commercial NAs (Refined Merichem) resulted in detectable tissue residues in native amphibians (northern leopard frogs, Lithobates pipiens), and 2) whether such exposure would produce clinical or subclinical toxicity. Frogs were kept in NA solutions (0, 20, or 40 mg/L) under saline conditions comparable to that on reclaimed wetlands in the Athabasca oil sands for 28 days. These exposures resulted in proportional NA concentrations in muscle tissue of the frogs, estimated by gas chromatography-mass spectrometry analyses. Detailed studies determined if the increasing concentrations of NAs, and subsequently increased tissue NA levels, caused a proportional compromise in the health of the experimental animals. Physiological investigations included innate immune function, thyroid hormone levels, and hepatic detoxification enzyme induction, none of which differed in response to increased exposures or tissue concentrations of NAs. Body mass did increase in both the salt- and NA-exposed animals, likely related to osmotic pressure and uptake of water through the skin. Our results demonstrate that commercial NAs are absorbed and deposited in muscle tissue, yet they show few negative physiological or toxicological effects on the frogs.
Faculty of Veterinary Medicine, University of Calgary, TRW 2D20, 3280 Hospital Drive NW, Calgary AB Canada T2N 4Z6. judit.smits@ucalgary.ca
Judit E G
JE
Smits
Blair D
BD
Hersikorn
Rozlyn F
RF
Young
Phillip M
PM
Fedorak
D000818:Animals; D002264:Carboxylic Acids / Q000032:analysis* / Q000633:toxicity*; D019363:Cytochrome P-450 CYP1A1 / Q000032:analysis; D004784:Environmental Monitoring; D005260:Female; D008401:Gas Chromatography-Mass Spectrometry; D007107:Immune System / Q000187:drug effects; D008099:Liver / Q000187:drug effects / Q000201:enzymology; D018482:Muscle, Skeletal / Q000737:chemistry*; D061329:Oil and Gas Fields / Q000737:chemistry; D010578:Petroleum / Q000032:analysis; D011894:Rana pipiens / Q000378:metabolism / Q000502:physiology*; D013963:Thyroid Hormones / Q000097:blood; D014018:Tissue Distribution; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000633:toxicity; D015430:Weight Gain / Q000187:drug effects; D053833:Wetlands
D002264:Carboxylic Acids; D010578:Petroleum; D013963:Thyroid Hormones; D014874:Water Pollutants, Chemical; D019363:Cytochrome P-450 CYP1A1; C046170:naphthenic acid