Extracellular calcium ion pool

The extracellular calcium ion pool refers to the concentration of ionized calcium (Ca2+) maintained within the interstitial fluid and blood plasma, which is vital for a wide array of physiological processes. This pool serves as a critical signaling reservoir, facilitating the initiation of muscle contraction, the release of neurotransmitters at neuronal synapses, and the activation of the coagulation cascade required for blood clotting [1][2]. Homeostatic regulation of this pool is extremely tight, primarily managed by the parathyroid glands, kidneys, and bone through the actions of parathyroid hormone (PTH) and vitamin D [3]. The primary molecular sensor for this pool is the Calcium-sensing receptor (CaSR), a G protein-coupled receptor that detects minute fluctuations in extracellular calcium and triggers compensatory responses [4]. While the pool itself is a physiological compartment rather than a discrete molecular target, it is the functional focus of various therapies; for example, calcium salts are used to treat hypocalcemia, while calcimimetics like cinacalcet target the CaSR to indirectly lower the extracellular calcium concentration in patients with hyperparathyroidism [4][5].

Other names

Extracellular calciumIonized calcium poolSerum calciumPlasma calciumECF calcium

Direct supplementation of calcium ions to increase pool concentration, chemical chelation to reduce free ionized calcium, or pharmacological modulation of the Calcium-sensing receptor (CaSR) to alter systemic hormonal regulation of the pool.