Elevation of cyclic AMP levels and adenylate cyclase activity in duodenal mucosa from vitamin D-deficient rats by 1alpha,25-dihydroxycholecalciferol (1alpha,25-(OH)2D3).

A single 270 ng dose of 1alpha,25-(OH2D3 rpoduced elevations in cyclic AMP content and adenylate cyclase activity in duodenal mucosa from previously vitamin D-deficient rats. No changes in jejunal or ileal cyclic AMP levels or duodenal cyclic GMP levels were observed. Since 1alpha,25-(OH)2D3 increased both baseline and NaF-stimulated adenylate cyclase activity, it is possible that the vitamin leads to enhanced enzyme synthesis. While parallel changes in duodenal cyclic AMP levels and active calcium absorption in response to 1alpha,25-(OH)2D3 were observed at 6,12,24 and 48 hr after treatment, increases in calcium absorption were observed at 3 hr in duodenum and at 48 hr in ileum in the absence of changes in cyclic AMP levels. Further studies will be required to determine whether or not the changes in duodenal cyclic AMP levels are direct or indirect effects of 1alpha,25-(OH)2D3 administration, and to determine the role, if any, of this nucleotide in the hormones' effect on intestinal calcium absorption.