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Background: Although glyceryl trinitrate (GTN) is used extensively to treat angina and heart failure, little is known about its effects on the conceptus during organogenesis. The goal of these studies was to investigate the effects of GTN in a model organism, the quail (Coturnix coturnix japonica) embryo., Methods: To identify the effects of GTN on quail embryo development, fertilized quail eggs (n = 10-12 eggs/group) were injected with GTN (0, 4.4, 44, or 440 μM) at Hamburger-Hamilton (HH) stage 0, 9, or 19 and examined 7 days later. Next, HH 9 embryos were injected with GTN (0, 0.88, 4.4, 8.8, 44, 88, and 440 μM, in 20 μL per egg) and examined 24-hours, 48-hours, or 72-hours postinjection. Finally, the developing eye on one side was exposed to GTN (44 μM) ex ovo and the tissue was probed for the presence of nitrated proteins., Results: In ovo GTN exposure induced a dose-dependent increase in the number of malformed viable quail embryos with a maximal effect in HH 9 embryos. Microphthalmia, craniofacial, heart, and neural tube defects were elevated in GTN-exposed embryos. An increase in nitrated proteins was observed in the developing eye region of embryos exposed ex ovo to GTN., Conclusions: GTN treatment induced a variety of malformations in quail embryos. The presence of nitrated proteins suggests that organic nitrates, such as GTN, generate reactive nitrogen species. We hypothesize that GTN perturbations in the redox status of the embryo may underlie its developmental toxicity., (Copyright © 2011 Wiley-Liss, Inc.)