AJP - Endocrinology and Metabolism, Vol 267, Issue 6 E837-E841, Copyright © 1994 by American Physiological Society
Calcium uptake by chorioallantoic membrane: effects of vitamins D and K
M. A. Elaroussi and H. F. DeLuca
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706.
The chorioallantoic membrane (CAM) of birds is an epithelial tissue that
actively transports large amounts of Ca during embryonic development. In
this study the effect of vitamins D and K on Ca uptake by the CAM was
studied. Four dietary treatments were used to produce eggs that are the
following: deficient in vitamins D and K (-D/-K), sufficient in both
(+D/+K), or deficient in one and sufficient in the other (-D/+K or +D/-K).
Vitamin D-deficient (-D) Japanese quail embryos (from hens fed
1,25-dihydroxyvitamin D3) do not hatch because of severe Ca deficiency
resulting from their inability to obtain Ca from shell, whereas vitamin K
deficiency results in only 14% reduction in hatchability. The results
demonstrate that Ca uptake by CAM is vitamin D dependent and only slightly
vitamin K dependent. Ca-binding activity of CAM extracts was unchanged by
vitamin K deficiency, and only a small increase was provided by vitamin D
treatment. Vitamin D stimulated both Ca entry and exist from the chorion
cells as indicated by the increased accumulated 45Ca in +D embryos. We
conclude that vitamin D is essential for the utilization of eggshell Ca by
the developing embryo and hence its survival, suggesting that Ca transport
across the CAM is largely a vitamin D-dependent process.
