Impact of egg storage on carbonic anhydrase activity during early embryogenesis in the turkey

Carbonic anhydrase is an enzyme that plays important roles in the conversion of carbon dioxide to bicarbonate, acid-base balance, and in subembryonic fluid formation in the early Japanese quail embryo. While turkey egg storage longer than 10 d is known to increase the rate of embryo mortality, little is known of the biological mechanisms that contribute to this phenomenon. In this study, we examined the impact of turkey egg storage on carbonic anhydrase activity in the freshly laid egg through 72 h of incubation. Carbonic anhydrase activity, which was not affected by egg storage for 21 d at 18 degrees C, was first observed in the germ wall, that area of yolk subjacent to the area opaca, after 24 h incubation. By 48 and 72 h, the yolk sac had formed with the yolk sac endoderm and was strongly positive for carbonic anhydrase. In contrast, mesodermal and ectodermal layers were negative. Our observations support recent studies showing carbonic anhydrase activity associated with the endodermal cell of the yolk sac in Japanese quail embryos and that such activity appears to be involved with subembryonic fluid formation in the turkey. This work also demonstrated that if an embryo survives cold egg storage, carbonic anhydrase activity does not appear to be affected.