Calcium absorption is increased by -

Ans. is 'a' i.e., Acidic Ph o With an average intake of 1000 mg of calcium its net intestinal absorption is only 150-250 mg/day. o Calcium is absorbed mainly in the duodenum and Jejunum (proximal intestine)0 by an active transport mechanism regulated by 1,25 (OH)2 D3 (calcitriol) Q. o Parathormone indirectly promotes absorption of calcium0 by increasing the renal synthesis of 1,25 (OH) 2 D3.Dietary lactose, proteins0and an acidic environment promote calcium absorption Q.. o On the other hand, phytates, phosphates, oxalates, tetracycline and and alkaline environment impair calcium absorption Q. o Calcium is transported across the brush border of intestinal epithelial cells via channels known as transient receptor potential vantioid type 6 (TRPV6) and binds to an intracellular protein known as catbindin. o Calbindin sequesters the absorbed calcium so that it does not disturb the epithelial signaling process that involve calcium. o The absorbed Ca+2 is thereby delivered to the basolateral membrane of the epithelial cells, from where it can be transported into the blood stream by either a Sodium/Calcium exchanger (NCX1) or a calcium-dependent ATPase.