Age-related changes in the response of intestinal cells to 1α,25(OH)2-vitamin D3

► 1α,25(OH)2D3 signaling in intestine is impaired with aging. ► 1α,25(OH)2D3-VDR binding is reduced in old avian and mammalian intestinal cells. ► Hormone regulation of intestinal Ca2+ uptake and homeostasis is impaired with age. ► Defective 1α,25(OH)2D3 regulation of intestinal cell mitogenic cascades with ageing.