Protection from TCDD-induced precardiac edema by COX2 inhibitor. Embryos, treated with a COX2 inhibitor (24 μM NS398), were exposed to TCDD (1 ppb) or vehicle alone (Control), beginning at 24 hpf. At 55 hpf, precardial cavity was determined as an index of TCDD-induced edema (precardiac edema). Results are expressed as percentage of control (mean ± SEM, N = 20). Significant differences in precardiac area between groups were determined by one-way ANOVA followed by Tukey-Kramer test (p < 0.05). Values with different letters are significantly different.