Distribution of Ornithine Decarboxylase Activity Induced by lα,25-Dihydroxyvitamin D3in Chick Duodenal Villus Mucosa

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Abstract
The distribution of enzymes involved in polyamine synthesis and that of the polyamine levels were investigated in the duodenal mucosa of vitamin D-deficient chicks and those supplemented with lα,25-dihydroxyvitamin D3 [1α,25- (OH)2D3]. Duodenal epithelial cells were isolated sequentially from the villus tip to the crypt region using a nonenzymatic method. In vitamin D-deficient chicks, the activities of ornithine decarboxylase (ODC) and S-adenosylmethionine decarboxylase were markedly higher in the crypt cells than in the villus cells. Similar gradients were observed in the distribution of putrescine and spermidine. Six hours after iv administration of 625 ng lα,25-(OH)2D3, ODC activity and putrescine levels markedly increased both in the villus and crypt region. The rate of the increase in ODC activity and putrescine levels, however, was much higher in the villus than in the crypt region. Neither S-adenosylmethionine decarboxylase activity nor spermidine levels were affected by the treatment with 1α,25-(OH)2D3. To investigate differential uptake of 1α,25-(OH)2D3 in the duodenal mucosa, 0.1 nmol 1α,25-(OH)32[3H]D3 with or without a 200-fold excess of unlabeled 1α,25-(OH)2D3 was injected into rachitic chicks, and epithelial cells were sequentially isolated 2 h later. The radioactivity specifically incorporated in the nuclear fraction was distributed uniformly from the villus tip to crypt cells. The cytoplasmic receptor for 1α,25-(OH)2D3 was similarly distributed in the crypt and villus cells. These results suggest that 1α,25-(OH)2D3 plays a physiological role in cellular activities not only in the villus but also in the crypt region through polyamine biosynthesis.