Abstract
Embryonic chick duodenum can be maintained in organ culture in contact with a serum-free medium with excellent preservation of mucosal structure. The presence of vitamin D3 in the culture medium induces de novo synthesis of a calcium-binding protein (CaBP) and stimulates uptake and mucosal to serosal transport of calcium in the cultured intestine. Using this system, it was found that vitamin D3 in the culture medium elevated duodenal cyclic AMP concentration after only 3hr of incubation. This response was prior to induction of CaBP and stimulation of calcium accumulation. Following a decline to control levels at 6 hr, there was a continuous rise in duodenal cyclic AMP, paralleling CaBP synthesis and enhanced calcium uptake, throughout the 48-hr culture period. Addition of either dibutyryl cyclic AMP (dbcAMP) or theophylline to the medium at lmM stimulated 45Ca accumulation by the intestine regardless of the presence of vitamin D3,although stimulation was greatest in the presence of the sterol, and the eff...
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