Calcium (intrazellulär): the pathway in the body

Calcium (intrazellulär) is part of the pathway “Calcium”. This page shows the whole pathway; the station of Calcium (intrazellulär) is highlighted.

Where this laboratory value sits: Calcium in food — dairy products, water. In food, calcium is present as a salt. It dissolves in the stomach and upper small intestine; only dissolved, free calcium can reach the gut wall at all. Source 1

In brief

Calcium is a mineral, most of which is stored in bone. Inside cells, a brief rise in free calcium acts as a signal that switches enzymes on and off.

The pathway step by step

1. Calcium in food → Into the gut cell TRPV6 channel · Calcitriol With small amounts, the channel TRPV6 lets calcium into the cell, and the binding protein calbindin carries it onward. Calcitriol, the active form of vitamin D, controls both. Source 1
2. Into the gut cell → Calcium in blood PMCA1b, NCX1 · ATP At the back of the gut cell, the pump PMCA1b and the exchanger NCX1 move calcium into the blood. There, about half is free; the rest is bound to albumin and acids. Source 1
3. Calcium in blood → Bone as a store · Parathyroid hormone, Calcitriol By far the largest share of calcium sits in bone. Parathyroid hormone and calcitriol control how much of it passes into the blood and how much is laid down again. Source 1
4. Stimulus at cell surface → IP3 as messenger Phospholipase C · PIP2 Phospholipase C splits a particular lipid of the cell membrane. This releases IP3, a small messenger that moves freely through the cell interior. Source 2
5. IP3 as messenger → Calcium rise IP3 receptor IP3 opens channels on the endoplasmic reticulum, the cell's calcium store. Calcium flows out, and its level inside the cell rises steeply for a short time. Source 2, 3
6. Calcium rise → Calmodulin Calcium binds to calmodulin, a small protein. As a result, calmodulin changes shape and can now dock onto other proteins. Source 3
7. Calmodulin → Kinases, calcineurin The altered calmodulin switches enzymes on: CaM kinases attach phosphate groups, and the phosphatase calcineurin removes them again. This turns the signal into a response of the cell. Source 3
8. Calcium rise → Back into the store SERCA pump · ATP The SERCA pump moves calcium back into the endoplasmic reticulum, using ATP. The signal thus ends as quickly as it began. Source 2
9. Back into the store → Out of the cell PMCA, NCX · ATP Pumps and exchangers in the cell membrane move part of the calcium outside. At rest, this keeps the cell's calcium level very low; only then does a rise remain readable as a signal. Source 3, 4

Cofactors in this pathway

• Vitamin D — As calcitriol, controls the TRPV6 channel and the binding protein calbindin in the gut Source 1In the ORY catalogue as a laboratory value: Vitamin D
• Magnesium — Needed for the release of parathyroid hormone, which controls exchange with bone Source 6In the ORY catalogue as a laboratory value: Magnesium
• Sodium — Drives the NCX exchanger, which moves calcium out of the cell in exchange for sodium Source 2In the ORY catalogue as a laboratory value: Natrium (intrazellulär)
• ATP — Energy carrier of the PMCA and SERCA pumps, which remove calcium from the cytosol Source 2
• Inositol — Building block of PIP2, from which phospholipase C releases the messenger IP3 Source 2

What acts on this pathway

• Acid-reducing drugs — Calcium carbonate needs stomach acid to dissolve. In one study, uptake from calcium carbonate was lower under a proton pump inhibitor than without one. Source 5

Sources

1. Christakos S, Li S, De La Cruz J et al. Vitamin D and the intestine: Review and update. J Steroid Biochem Mol Biol 2020 · PubMed 31655181
2. Berridge MJ, Bootman MD, Roderick HL. Calcium signalling: dynamics, homeostasis and remodelling. Nat Rev Mol Cell Biol 2003 · PubMed 12838335
3. Clapham DE. Calcium signaling. Cell 2007 · PubMed 18083096
4. Prakriya M, Lewis RS. Store-Operated Calcium Channels. Physiol Rev 2015 · PubMed 26400989
5. O'Connell MB, Madden DM, Murray AM et al. Effects of proton pump inhibitors on calcium carbonate absorption in women: a randomized crossover trial. Am J Med 2005 · PubMed 15989913
6. de Baaij JH, Hoenderop JG, Bindels RJ. Magnesium in man: implications for health and disease. Physiol Rev 2015 · PubMed 25540137

Whole pathway: Calcium

Related pathways

• GABA, glutamate and glutamine — Magnesium, Natrium (intrazellulär)
• Creatinine — Magnesium, Natrium (intrazellulär)

As of 2026-09-16. Draft written by Claude to schema v2; sources checked in PubMed; expert review pending
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