Calcium-binding protein and calcium absorption in the laying quail (Coturnix coturnix japonica)

A vitamin D3-dependent calcium-binding protein (CaBP) has been found in the intestinal mucosa of Japanese quail (Coturnix coturnix japonica). This protein is similar, if not identical to that of the chick (Gallus domesticus). A similar protein fraction appears also in uterine mucosa of laying quail. Both intestinal and uterine CaBP levels are higher in laying than in non-laying quails. Uterine CaBP was higher during egg shell formation than during uterine inactivity. The slight corresponding difference in the intestinal CaBP was not significant. Intestinal calcium absorption measured with 91Y as a reference substance was higher in birds during formation of egg shell than in those with inactive uteri. The possible role of CaBP in calcium translocation is discussed.