Elevation of Cyclic AMP Levels and Adenylate Cyclase Activity in Duodenal Mucosa from Vitamin D-Deficient Rats by 1α,25-Dihydroxycholecalciferol (1α,25-(OH)2D3)

Abstract

A single 270 ng dose of lα,25-(OH)₂D₃ produced 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 lα,25-(OH)₂ D₃ 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 lα,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 lα,25-(OH)₂D₃ administration, and to determine the role, if any, of this nucleotide in the hormones’ effect on intestinal calcium absorption.