SOME POSSIBLE MECHANISMS OF FORMATION OF CARBONATE FRACTION OF EGG SHELL CALCIUM CARBONATE

1. 1. Solutions of Ca45Cl2 and NaHC14O3 were injected into the blood stream of anaesthetized hens which were either actively forming an egg shell or had no egg present in the oviduct. 2. 2. Sciatic arterial and shell gland venous blood samples showed that whereas during shell formation there was an arterio-venous Ca45 difference of 57 percent, there was no arterio-venous C14 difference. When there was no egg present in the shell gland there was no arterio-venous difference with either of the isotopes. 3. 3. In similarly injected, shell-forming birds it was found that after 2 hr 38-45 per cent of the Ca45 dose and 1-3 per cent of the C14 dose had been deposited in the shell. 4. 4. It is considered that these results invalidate the theory which suggests that the carbonate fraction of the egg shell is derived from blood bicarbonate ions (Gutowska & Mitchell) and supports, but does not prove, the theory that it is derived from the shell gland metabolic CO2 (Diamantstein). © 1969.