AJP - Endocrinology and Metabolism, Vol 248, Issue 3 281-E285, Copyright © 1985 by American Physiological Society
Effect of vitamin D3 metabolites on calcium and phosphorus metabolism in chick embryos
L. E. Hart and H. F. DeLuca
The biochemical nature of the physiological defect found in chick embryos
from hens supported on 1,25-dihydroxyvitamin D3 as their sole source of
vitamin D is described. Vitamin D-deficient hens (44-wk-old) were divided
into six groups of five and dosed daily for 19 wk with either 2.0
micrograms of 25-hydroxyvitamin D3, 2.0 micrograms of
24,24-difluoro-25-hydroxy-vitamin D3, 0.4 micrograms of
1,25-dihydroxyvitamin D3, 2.0 micrograms of 24,25-dihydroxyvitamin D3, 0.4
micrograms of 1,25-dihydroxyvitamin D3 plus 2.0 micrograms of
24,25-dihydroxyvitamin D3, or vehicle only. Normal embryonic development
was found in eggs from hens given 25-hydroxyvitamin D3 or
24,24-difluoro-25-hydroxyvitamin D3, whereas embryos from hens given
1,25-dihydroxyvitamin D3, 24,25-dihydroxyvitamin D3, or their combination
were abnormal and failed to hatch. Embryos from hens fed
1,25-dihydroxyvitamin D3 and/or 24,25-dihydroxyvitamin D3 had vitamin D
deficiency: low bone ash, low plasma calcium, low total body calcium, and
extremely high plasma phosphorus. Because the shell is the major source of
calcium for the developing embryo, calcium transport from the shell to the
embryos across the chorioallantoic membrane apparently fails, giving rise
to the observed defects in embryonic development.
