Abstract
Calcium (Ca) absorption occurs by two mechanisms, nonsaturable paracellular absorption and saturable transcellular absorption. The activity of these mechanisms depends on the concentration of Ca in the diet. At high dietary Ca concentration, the nonsaturable mechanism is more active, whereas at low dietary Ca concentration, the saturable mechanism is more involved. The saturable mechanism is vitamin-D dependent, because the expression of genes related to the transcellular transport may be influenced by the active form of vitamin D. Increasing dietary Ca decreases the mRNA expression of transient receptor potential cation channel, subfamily V, member 6 (TRPV6), which is used for absorption of Ca into the enterocytes in the jejunum. However, this does not result in less absorption of Ca, because as dietary Ca increases, an increased proportion of Ca is absorbed via the paracellular route in the small intestine and the total percentage of Ca that is absorbed is almost constant regardless of dietary Ca concentration. High concentrations of dietary Ca will also reduce the mRNA expression in the kidneys of TRPV6, TRPV5, S100 calcium binding protein G, and calbindin 1, but because there is no paracellular reabsorption of Ca in the kidneys excretion of Ca in the urine is increased as dietary Ca concentration increases. As a consequence, body Ca concentrations are primarily regulated in the kidneys.
Original language | English (US) |
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Title of host publication | Phytate Destruction - Consequences for Precision Animal Nutrition |
Publisher | Wageningen Academic Publishers |
Pages | 217-224 |
Number of pages | 8 |
ISBN (Electronic) | 9789086868360 |
ISBN (Print) | 9789086862900 |
DOIs | |
State | Published - Jan 1 2016 |
Keywords
- Calbindin
- Calcium channels
- Paracellular absorption
- Transcellular absorption
- Vitamin D receptor
ASJC Scopus subject areas
- General Engineering
- General Agricultural and Biological Sciences