Fenitrothion, an organophosphate, affects running endurance but not aerobic capacity in fat-tailed dunnarts ( Sminthopsis crassicaudata)

• Published in: Chemosphere (Oxford) Vol. 72; no. 9; pp. 1315 - 1320
• Main Authors: Buttemer, William A., Story, Paul G., Fildes, Karen J., Baudinette, Russell V., Astheimer, Lee B.
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01-07-2008; Elsevier
• Subjects: adverse effects; aerobic metabolism; Aerobiosis - drug effects; animal models; Animal, plant and microbial ecology; Animals; Applied ecology; Biological and medical sciences; Body Temperature Regulation - drug effects; Brain - drug effects; Brain - enzymology; Cholinesterase Inhibitors - blood; Cholinesterase Inhibitors - toxicity; Cholinesterases - blood; Dasyuridae; Data Interpretation, Statistical; dosage; Ecotoxicology, biological effects of pollution; energy metabolism; exercise; Fenitrothion; Fenitrothion - blood; Fenitrothion - toxicity; Fundamental and applied biological sciences. Psychology; General aspects; Insecticides - blood; Insecticides - toxicity; laboratory animals; locomotion; Male; Mammalia; Marsupial; Marsupialia - physiology; metabolism; Metabolism - drug effects; nontarget organisms; oral administration; Organophosphate; oxygen; Oxygen consumption; peak metabolic rate; Pesticide Residues - blood; physical activity; Physical Endurance - drug effects; physical fitness; running; Running - physiology; Running endurance thermogenesis; signs and symptoms (animals and humans); skeletal muscle; Sminthopsis crassicaudata; sublethal effects; temporal variation; Thermogenesis - drug effects; Vertebrates: general zoology, morphology, phylogeny, systematics, cytogenetics, geographical distribution; wild animals; Oxygen consumption; Marsupial; Organophosphate; Running endurance thermogenesis; Fenitrothion; Vertebrata; Mammalia; Marsupialia; Organophosphorus compounds; Aerobe; Respiration
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2008.04.054

We measured aerobic metabolism during cold exposure and exercise performance (run duration and oxygen consumption while running at 1
m
s
−1) in the fat-tailed dunnart
Sminthopsis crassicaudata, a dasyurid marsupial, before and after ingestion of 30
mg
kg
−1 of fenitrothion, an organophosphate (OP) pesticide. Running endurance of OP-exposed animals was less than half that of control animals over the first 3 days after dosing and 55% of control animal endurance on day 5 post-dose. Despite these declines, peak metabolic rate at this running speed (9.3 times basal metabolic rate; BMR) was unaffected by OP exposure. Peak metabolic rate (PMR) and cumulative oxygen consumption during a 1-h exposure to conditions equivalent to −20
°C did not differ between OP-treated and control dunnarts, with PMR averaging 11 times BMR. We conclude that fenitrothion-induced exercise fatigue is not due to limitations in oxygen or substrate delivery to muscle or in their uptake
per se, but more likely relates to decreased ability to sustain high-frequency neuromuscular function. The persistence of locomotor impairment following OP exposure in otherwise asymptomatic animals emphasizes the importance of using performance-based measures when characterising sublethal effects of pesticide exposure in an ecological context.