The effect of avian uterine fluid on the growth behavior of calcite crystals

Eggshell formation takes place-on the eggshell membrane in an acellular med ium, the uterine fluid that contains the inorganic minerals and precursors of the organic matrix. The high degree of eggshell structure could be due t o an interaction between calcium carbonate and the organic matrix. The aim of this study was to demonstrate such an interaction by measuring the effec t in vitro of uterine fluid collected at various phases of shell formation on precipitation kinetics, size, and morphology of calcite crystals. The SD S-PAGE profiles of the organic constituents differed between the different phases of eggshell formation. The predominant constituents were ovalbumin a nd ovotransferrin at the initial phase and lysozyme, ovocleidin-17, ovocaly xin-32, 36- and 21-kDa bands, and ovocleidin-116 at the growth phase. These proteins were numerous in the terminal phase and showed an increased stain ing of the 32- and 66-kDa bands and appearance of very low molecular weight bands. The precipitation lag time was shortened in proportion to the prote in concentration at the initial stage. The effect was observed with a lower magnitude in the presence of constituents of growth and terminal phases. C rystal size was smaller in the presence of constituents from the three stag es compared with the control. Components from the initial phase induced the formation of twinned crystals and of rounded corners in the rhombohedric c rystals. The presence of components from the growth and terminal phases str ongly modified the morphology of the calcite crystals. The majority of the corners became rough and developed curved faces. These observations confirm the interaction of the uterine fluid with calcite and its contribution to eggshell structure.