The role of vitamin D in chorioallantoic membrane calcium transport.
1,25-Dihydroxyvitamin D3 (1,25-(OH)2D3) is essential for the transport of eggshell calcium to the embryo across the chorioallantoic membrane (CAM). CAM contains the vitamin D receptor that increases following 1,25-(OH)2D3 injection into embryos at day 10 of incubation. Further, a single injection of 100 ng of 1,25-(OH)2D3 into vitamin D-deficient quail eggs at day 10 of incubation resulted in a significant increase in both body and yolk calcium. This is accompanied by an increase in carbonic anhydrase from low levels in deficiency to normal levels. Acetazolamide (AZ), a specific carbonic anhydrase inhibitor injected into the quail embryos, caused hypocalcemia and hyperphosphatemia. This is similar to the hypocalcemia and hyperphosphatemia found in vitamin D-deficient embryos. These results suggest that one mechanism of action of vitamin D in the mobilization of eggshell calcium is the activation of carbonic anhydrase that acidifies the calcium carbonate shell.
Elaroussi
M A
MA
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706.
Uhland-Smith
A
A
Hellwig
W
W
DeLuca
H F
HF
D000086:Acetazolamide / Q000494:pharmacology; D000482:Allantois / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D002117:Calcitriol / Q000172:deficiency / Q000494:pharmacology / Q000502:physiology*; D002118:Calcium / Q000097:blood*; D002256:Carbonic Anhydrases / Q000378:metabolism; D002823:Chorion / Q000378:metabolism*; D003370:Coturnix / Q000196:embryology*; D010758:Phosphorus / Q000097:blood; D018167:Receptors, Calcitriol / Q000378:metabolism
D018167:Receptors, Calcitriol; D010758:Phosphorus; D002256:Carbonic Anhydrases; D002117:Calcitriol; D000086:Acetazolamide; D002118:Calcium