Calcium buffering describes the processes which help stabilise the concentration of free calcium ions within cells, in a similar manner to how pH buffers maintain a stable concentration of hydrogen ions.[1] The majority of calcium ions within the cell are bound to intracellular proteins, leaving a minority freely dissociated.[2] When calcium is added to or removed from the cytoplasm by transport across the cell membrane or sarcoplasmic reticulum, calcium buffers minimise the effect on changes in cytoplasmic free calcium concentration by binding calcium to or releasing calcium from intracellular proteins. As a result, 99% of the calcium added to the cytosol of a cardiomyocyte during each cardiac cycle becomes bound to calcium buffers, creating a relatively small change in free calcium.[2]
The regulation of free calcium is of particular importance in excitable cells like cardiomyocytes[3] and neurons.[4] Within these cells, many intracellular proteins can act as calcium buffers. In cardiac muscle cells, the most important buffers within the cytoplasm include troponin C, SERCA, calmodulin, and myosin, while the most important within calcium buffer within the sarcoplasmic reticulum is calsequestrin.,[2][5] The effects of calcium buffers depends on their affinity for calcium, as well as the speed with which they bind and release it.[6]
^Gilabert JA (2012). "Cytoplasmic calcium buffering". Advances in Experimental Medicine and Biology. 740: 483–98. doi:10.1007/978-94-007-2888-2_20. ISBN 978-94-007-2887-5. PMID 22453955. {{cite journal}}: Cite journal requires |journal= (help)
^ abcM., Bers, D. (2001). Excitation-contraction coupling and cardiac contractile force (2nd ed.). Dordrecht: Kluwer Academic Publishers. ISBN 9780792371588. OCLC 47659382.{{cite book}}: CS1 maint: multiple names: authors list (link)
^Smith GL, Eisner DA (May 2019). "Calcium Buffering in the Heart in Health and Disease". Circulation. 139 (20): 2358–2371. doi:10.1161/CIRCULATIONAHA.118.039329. PMC 6520234. PMID 31082292.
^Schwaller B (November 2010). "Cytosolic Ca2+ buffers". Cold Spring Harbor Perspectives in Biology. 2 (11): a004051. doi:10.1101/cshperspect.a004051. PMC 2964180. PMID 20943758.
^Briston SJ, Dibb KM, Solaro RJ, Eisner DA, Trafford AW (November 2014). "Balanced changes in Ca buffering by SERCA and troponin contribute to Ca handling during β-adrenergic stimulation in cardiac myocytes". Cardiovascular Research. 104 (2): 347–54. doi:10.1093/cvr/cvu201. PMC 4240166. PMID 25183792.
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