Abstract
Embryonic chick intestine maintained in organ culture responded to vitamin D3 and its metabolites 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol by synthesis of calcium-binding protein and enchanced calcium-45 uptake. The dihydroxy metabolite was by far the most potent inducer of the protein and also acted more rapidly than vitamin D3 to stimulate isotope uptake. Despite its lower potency, vitamin D3 itself was effective.