MOBILIZATION OF SHELL CALCIUM BY THE CHICK CHORIOALLANTOIC MEMBRANE IN-VITRO

Two explants of shell were removed from each of several fertile eggs o f domestic fowl at different times during incubation. The chorioallant oic membrane (CAM) was removed from one of the explants (SHELL ONLY) a nd was left in situ on the other (SHELL+CAM). Explants were cultured f or 24, 48 or 96 h at 37 degrees C and 5 % CO2 in air in individual Pet ri dishes containing Dulbecco's modified Eagle's medium, bovine serum albumin, penicillin and streptomycin. Both SHELL+CAM and SHELL ONLY ex plants released calcium into the culture medium, but the former releas ed considerably more calcium than the latter. More calcium was release d by SHELL+CAM explants taken from older eggs than from younger ones, but the age of the donor eggs did not affect release of calcium by SHE LL ONLY explants. In addition, release of calcium by SHELL+CAM explant s exceeded that shown by SHELL ONLY explants for multiple 24 h interva ls. However, the capacity for sustained release of calcium by SHELL+CA M explants declined with age and maturity of the CAM, Manipulations th at lead to the death of the CAM abolish the capacity for SHELL+CAM exp lants to release more calcium than SHELL ONLY explants. Differential r elease of calcium by SHELL+CAM explants was not attributable to calciu m present in the CAM at the onset of culture or to non-specific degrad ation of the shell by intracellular constituents released as a result of the death of the CAM. Taken in concert, these results indicate that the CAM mobilizes calcium from the eggshell during in vitro culture.