Calcium uptake by chorioallantoic membrane: effects of vitamins D and K.
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.
Elaroussi
M A
MA
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706.
DeLuca
H F
HF
D000482:Allantois / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism; D002823:Chorion / Q000378:metabolism*; D003370:Coturnix / Q000196:embryology; D014807:Vitamin D / Q000494:pharmacology*; D014812:Vitamin K / Q000494:pharmacology*
D002135:Calcium-Binding Proteins; D014812:Vitamin K; D014807:Vitamin D; D002118:Calcium