Strain-dependent effect of ethanol on ventricular septal defect frequency in White Leghorn chick embryos

We have tested the potential of a single dose of ethanol (0.20 ml 50% ethanol in chick Ringer's saline (CRS) administered into the air sac) to produce ventricular septal defect (VSD) in three distinct commercially available strains of White Leghorn chick embryo: stress-resistant Dekalb Delta strain, Hy-Vac SPF type V, and Hy-Vac SPF type L. Eggs were controlled for both size and developmental stage (Hamburger-Hamilton stage 18-19) at time of injection. The frequency of VSD in Dekalb Delta embryos was 4.0% (1/25), in Hy-Vac SPF type L embryos 9.1% (3/33), and in Hy-Vac SPF type V embryos 38.9% (14/36). Statistical analysis with the two-tailed Fisher Exact Test indicated that frequencies were not significantly different (P = 0.3215) when Dekalb Delta and Hy-Vac type L embryos were compared. However, the frequency of VSD for Hy-Vac type V embryos was significantly greater than that for either the Dekalb Delta or the Hy-Vac type L embryos (P < 0.005). All VSDs observed were located within the crista supraventricularis. When Hy-Vac SPF type V embryos were exposed to either 0.20 ml 50% ethanol in CRS or to 0.20 ml CRS (controls), ethanol-treated embryos showed a VSD incidence of 34.1% compared with a 3.6% incidence in the controls (P = 0.0017). These data suggest that ethanol is the cause of VSD in this strain. From the results of this study, we are led to conclude that different commercial strains of White Leghorn chick embryo show different susceptibilities to the induction of VSD by ethanol.