Effects of Nitrite on Development of Embryos and Early Larval Stages of the Zebrafish (Danio rerio)

Abstract

Epidemiological studies suggest that high nitrate levels in food and water may cause birth defects or spontaneous abortions in humans. Experimental mammalian studies show that high nitrite levels adversely affect reproductive outcomes, but have not shown congenital malformations. Consequently, the teratogenic potential of nitrite is unclear. In this study, the effects of nitrite on development of zebrafish embryos and early larval stages were investigated. Eggs were exposed to ethanol (a known teratogen), nitrite, or nitrate for 24 or 96 hours, and larvae examined at 120 hours. Sublethal exposure to 300 mM ethanol for 24 hours caused severe pericardial and yolk sac edema, craniofacial and axial malformations, and swim bladder noninflation. The 96 hour LC 50 for nitrite was 411 mg/L. Less severe edema, craniofacial (but not axial) malformations, swim bladder noninflation, and immobility were observed after sublethal exposure to nitrite between 10 and 300 mg/L for 96 hours. Exposure to nitrite for 24 hours at concentrations as high as 2000 mg/L was not lethal. Only axial malformations and swim bladder noninflation were observed at 1500 mg/L. The results demonstrate that sublethal nitrite concentrations cause developmental defects. The type and magnitude of these defects differed after 24 and 96 hours of exposure.

Nitrate (NO3−) and nitrite (NO2−) are endocrine disruptors to downregulate expression of tyrosine hydroxylase and motor behavior through conversion to nitric oxide in early development of zebrafish

“…According to other studies in zebrafish, developmental defects, growth suppression and high mortality occur at much higher concentrations (100-300 mg/L) [6,7]. Although few studies indicated that nitrate and nitrite exposure exerts adverse effect on nervous system [8,31], to our knowledge so far this is the first study to reveal the specific effect of nitrate and nitrite on the activity of DA neurons.…”

“…Both acute and chronic exposures of nitrate and nitrite increase mortality and impair growth and reproduction [4,5]. Some studies in zebrafish at different life stages also reported toxic effects such as developmental defects, high mortality, and growth suppression [6,7]. Though some studies have shown the maternal exposure to high nitrate concentrations in drinking water and food may increase the risk of neuronal defects in infant [8], the information of specific mechanisms in the nervous system affected by nitrate and nitrite exposure is still limited.…”

Excessive Nitrite Affects Zebrafish Valvulogenesis through Yielding Too Much NO Signaling

“…Though the toxicological mechanisms and health risks of nitrite have been widely investigated [1], [10], little is known whether high level of nitrite is toxic to vertebrate early heart development and performance.…”

Investigating the Effect of Familiarity on Kin Recognition of Three‐Spined Stickleback (Gasterosteus aculeatus)

“…; Simmons et al. ), we took care not to take fish from aquaria where high nitrite levels (>0.1 mg/l) were measured within three days prior to the experiments. Focal individuals and most of the stimulus fish were used only once to avoid effects of multiple testing.…”

“…To minimize potential biases due to differences in intrinsic state (van Havre & FitzGerald 1988;Frommen et al 2012), we only used fish showing no signs of developing breeding coloration or egg production. As high nitrite levels are known to affect development, outer appearance and swimming behavior of fish (Wang et al 2006;Rodrigues et al 2007;Simmons et al 2012), we took care not to take fish from aquaria where high nitrite levels (>0.1 mg/l) were measured within three days prior to the experiments. Focal individuals and most of the stimulus fish were used only once to avoid effects of multiple testing.…”