Elevated nitrate alters the metabolic activity of embryonic zebrafish

• Published in: Environmental pollution (1987) 2018-04, Vol.235, p.180-185
• Main Authors: Conlin, Sarah M., Tudor, M. Scarlett, Shim, Juyoung, Gosse, Julie A., Neilson, Andrew, Hamlin, Heather J.
• Format: Article
• Language: English
• Subjects: additive effect; Animals; biochemical pathways; Chorion; Danio rerio; Embryo, Nonmammalian - drug effects; Embryo, Nonmammalian - metabolism; humans; Metabolic activity; Nitrate; nitrate nitrogen; Nitrates - metabolism; Nitrates - toxicity; Nitrogen Oxides - metabolism; oxygen consumption; Oxygen consumption rate; pollution; sodium chloride; sodium nitrate; Water Pollutants, Chemical - metabolism; Water Pollutants, Chemical - toxicity; water quality; wildlife; Zebrafish; Zebrafish - embryology; Zebrafish - metabolism
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2017.12.069

Nitrate accumulation in aquatic reservoirs from agricultural pollution has often been overlooked as a water quality hazard, yet a growing body of literature suggests negative effects on human and wildlife health following nitrate exposure. This research seeks to understand differences in oxygen consumption rates between different routes of laboratory nitrate exposure, whether via immersion or injection, in zebrafish (Danio rerio) embryos. Embryos were exposed within 1 h post fertilization (hpf) to 0, 10, and 100 mg/L NO3-N with sodium nitrate, or to counter ion control (CIC) treatments using sodium chloride. Embryos in the immersion treatments received an injection of 4 nL of appropriate treatment solution into the perivitelline space. At 24 hpf, Oxygen Consumption Rates (OCR) were measured and recorded in vivo using the Agilent Technologies XFe96 Extracellular Flux Analyzer and Spheroid Microplate. Immersion exposures did not induce significant changes in OCR, yet nitrate induced significant changes when injected through the embryo chorion. Injection of 10 and 100 mg/L NO3-N down-regulated OCR compared to the control treatment group. Injection of the 100 mg/L CIC also significantly down-regulated OCR compared to the control treatment group. Interestingly, the 100 mg/L NO3-N treatment further down-regulated OCR compared to the 100 mg/L CIC treatment, suggesting the potential for additive effects between the counter ion and the ion of interest. These data support that elevated nitrate exposure can alter normal metabolic activity by changing OCR in 24 hpf embryos. These results highlight the need for regularly examining the counter ion of laboratory nitrate compounds while conducting research with developing zebrafish, and justify examining different routes of laboratory nitrate exposure, as the chorion may act as an effective barrier to nitrate penetration in zebrafish, which may lead to conservative estimates of significant effects in other species for which nitrate more readily penetrates the chorion. [Display omitted] •Sodium nitrate effects on metabolic activity were assessed in 24 hpf embryos.•Counter ion control treatment used to extrapolate the effects of the nitrate ion.•Injection through the chorion yielded changes in OCR, but immersion did not.•Down-regulation in OCR at as little as 10 mg/L NO3-N after injection.•Additive effects between sodium and nitrate ions at 100 mg/L NO3-N after injection. Injection of nitrate treatments through the zebrafis