Regulation of Vitamin D Synthesis
Whether the renal cells produce 1,25- dihydroxycholecalciferol (the active metabolite) or 24,25-dihydroxycholecalciferol (the inactive metabolite) depends on the โstatusโ of Ca2+ in the body. When Ca2+ is sufficient, with an adequate dietary intake of Ca2+ and normal or increased plasma Ca2+ concentration, the inactive metabolite is preferentially synthesized because there is no need for more Ca2+. When Ca2+ is insufficient, with a low dietary intake of Ca2+ and decreased plasma Ca2+ concentration, the active metabolite is preferentially synthesized to ensure that additional Ca2+ will be absorbed from the gastrointestinal tract.
submitted by โazibird(279)
Costanzo Physiology 6th E p456
Regulation of Vitamin D Synthesis Whether the renal cells produce 1,25- dihydroxycholecalciferol (the active metabolite) or 24,25-dihydroxycholecalciferol (the inactive metabolite) depends on the โstatusโ of Ca2+ in the body. When Ca2+ is sufficient, with an adequate dietary intake of Ca2+ and normal or increased plasma Ca2+ concentration, the inactive metabolite is preferentially synthesized because there is no need for more Ca2+. When Ca2+ is insufficient, with a low dietary intake of Ca2+ and decreased plasma Ca2+ concentration, the active metabolite is preferentially synthesized to ensure that additional Ca2+ will be absorbed from the gastrointestinal tract.