The duodenal 1 alpha,25-dihydroxyvitamin D3 receptor in rats with experimentally induced diabetes

Studies in the rat with streptozotocin-induced diabetes of short and long duration revealed decreased circulating 1 alpha,25-dihydroxyvitamin D [1,25-(OH)2D] levels and an intact 1,25-(OH)2D3 duodenal cytosolic receptor with a sedimentation coefficient of 3.3S. Whereas no significant alterations in the equilibrium dissociation constant (Kd) were observed in the diabetic animals, the number of 1,25-(OH)2D3-binding sites was increased in the animals with short term (235 +/- 48 vs. 100 +/- 15 fmol/mg protein) and long term (521 +/- 60 vs. 119 +/- 15 fmol/mg protein) diabetes. The data are consistent with the hypothesis that alterations in intestinal calcium absorption previously observed in the diabetic state are due, at least in part, to dynamic relationships between circulating 1,25-(OH)2D concentrations and the number of intestinal 1,25(OH)2D3-binding sites.