Environmentally relevant concentrations of nitrate increase plasma testosterone concentrations in female American alligators (Alligator mississippiensis).
Anthropogenic nitrogen is a ubiquitous environmental contaminant that is contributing to the degradation of freshwater, estuarine, and coastal ecosystems worldwide. The effects of environmental nitrate, a principal form of nitrogen, on the health of aquatic life is of increasing concern. We exposed female American alligators to three concentrations of nitrate (0.7, 10 and 100mg/L NO3-N) for a duration of five weeks and five months from hatch. We assessed growth, plasma sex steroid and thyroid hormone concentrations, and transcription levels of key genes involved in steroidogenesis (StAR, 3β-HSD, and P450scc) and hepatic clearance (Cyp1a, Cyp3a). Exposure to 100mg/L NO3-N for both five weeks and five months resulted in significantly increased plasma testosterone (T) concentrations compared with alligators in the reference treatment. No differences in 17β-estradiol, progesterone, or thyroid hormones were observed, nor were there differences in alligator weight or the mRNA abundance of steroidogenic or hepatic genes. Plasma and urinary nitrate concentrations increased with increasing nitrate treatment levels, although relative plasma concentrations of nitrate were significantly lower in five month, versus five week old animals, possibly due to improved kidney function in older animals. These results indicate that environmentally relevant concentrations of nitrate can increase circulating concentrations of T in young female alligators.
School of Marine Sciences, Aquaculture Research Institute, University of Maine, 5751 Murray Hall, Orono, ME 04469, USA; Department of Obstetrics and Gynecology, Medical University of South Carolina, and Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, USA; Department of Biology, University of Florida, P.O. Box 118525, Gainesville, FL 32611, USA. Electronic address: heather.hamlin@maine.edu.
Heather J
HJ
Hamlin
Department of Biology, University of the South, 159 Spencer Hall, Sewanee, TN 37383, USA; Department of Biology, University of Florida, P.O. Box 118525, Gainesville, FL 32611, USA.
Thea M
TM
Edwards
Department of Obstetrics and Gynecology, Medical University of South Carolina, and Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, USA.
Jessica
J
McCoy
Department of Obstetrics and Gynecology, Medical University of South Carolina, and Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, USA; Department of Biology, University of Florida, P.O. Box 118525, Gainesville, FL 32611, USA.
Lori
L
Cruze
Department of Obstetrics and Gynecology, Medical University of South Carolina, and Hollings Marine Laboratory, 331 Fort Johnson Road, Charleston, SC 29412, USA; Department of Biology, University of Florida, P.O. Box 118525, Gainesville, FL 32611, USA.
Louis J
LJ
Guillette
D000489:Alligators and Crocodiles / Q000097:blood* / Q000235:genetics; D000818:Animals; D001835:Body Weight / Q000187:drug effects; D004785:Environmental Pollutants / Q000633:toxicity*; D004787:Environmental Pollution; D005260:Female; D012739:Gonadal Steroid Hormones / Q000097:blood; D009566:Nitrates / Q000097:blood / Q000633:toxicity* / Q000652:urine; D012333:RNA, Messenger / Q000378:metabolism; D013739:Testosterone / Q000097:blood*; D013963:Thyroid Hormones / Q000097:blood; D014158:Transcription, Genetic / Q000187:drug effects; D014481:United States
D004785:Environmental Pollutants; D012739:Gonadal Steroid Hormones; D009566:Nitrates; D012333:RNA, Messenger; D013963:Thyroid Hormones; D013739:Testosterone
Alligator; Androgen; Endocrine disrupting contaminant; Nitrate