EFFECT OF BETA-AMINOPROPRIONITRILE ON EGGSHELL FORMATION

1. Eggshells are bioceramic-biopolymer composites made by a cell-media ted deposition of an extracellular matrix which drives the organisatio n of the inorganic phase. Ultrastructurally, eggshells are composed of shell membranes, mammillary knobs, palisade, and cuticle. Shell membr anes are two nets of type X collagen-containing fibrils. On to these m embranes, the mammillary knobs, that is, the crystal nucleation sites, are deposited. Type X collagen is highly cross-linked and insoluble. 2. In order to evaluate the role of type X collagen cross-linking on e ggshell formation, hens were injected with different doses of beta-ami noproprionitrile, which specifically interferes with cross-link format ion. 3. Changes in egg size and shape were observed. Scanning electron micrographs analysis of these eggs demonstrated marked changes in cry stal growth and shell membrane structure and arrangement. A dot-blot a nalysis, using a monoclonal antibody against chicken type X collagen, shows a, dose-dependent increase in shell membrane collagen extractabi lity. 4. It is concluded that the formation of beta-aminoproprionitril e-sensitive cross-links among the type X collagen molecules of the she ll membranes play an essential role in normal eggshell formation.