Evaluation of a protocol for studying the chick chorioallantoic membrane in vitro

Explants of eggshell with and without the chorioallantoic membrane were tak en from fertile chicken eggs on day 16 of incubation and exposed in vitro t o inhibitors (acetazolamide and benzolamide) of carbonic anhydrase to deter mine if enzyme inhibition affected release of calcium from the shell. A sep arate experiment examined the effect of the metabolic poison dinitrophenol (DNP) on release of calcium from explants. Explants with the chorioallantoi s in situ released more calcium than those lacking the epithelium, but neit her the enzyme inhibitors nor DNP affected release of calcium. The lack of effect of the enzyme inhibitors could indicate that activity of carbonic an hydrase is not as important to the release of calcium from the eggshell as has been assumed. However, the absence of an effect of DNP instead indicate s that release of calcium mediated by the chorioallantois in vitro simply l acks physiological relevance. Thus, results of this investigation raise dou bts that the mechanism underlying release of calcium from the eggshell can be assessed in vitro. (C) 1999 Elsevier Science Inc. All rights reserved.