Calcium Secretion into Milk

  • Margaret C. Neville


Ionized calcium ([Ca2+]) is present in milk at concentrations around 3 mM, a concentration that drives the formation of complexes with citrate, phosphate, and casein, thereby generating compounds that carry the major portion of calcium in milk. In humans and cows, where it has been studied, changes in milk calcium appear to be regulated by the amount of citrate and casein in milk rather than changes in [Ca2+]. Most or all of the calcium in milk is likely derived through exocytosis of secretory vesicles derived from the Golgi compartment where a calcium ATPase mediates transport from the cytoplasm. The identity of the transporters is not yet certain but gene expression for the plasma membrane calcium ATPase, PMCA2bw, and the secretory pathway calcium ATPase, SPCA, is highly upregulated during lactation. Currently nothing appears to be known about the mechanisms that mediate transport of calcium across the basolateral membrane of the alveolar cell.


milk calcium secretion calcium ATPases casein micelle 



concentration of ionized calcium


endoplasmic reticulum


plasma membrane calcium transporter


yeast calcium ATPase


sarcoplasmic reticulum/ER calcium ATPase


secretory pathway calcium ATPase


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Copyright information

© Springer Science + Business Media, Inc. 2005

Authors and Affiliations

  • Margaret C. Neville
    • 1
    • 2
    • 3
  1. 1.University of Colorado Health Sciences Center at FitzsimmonsAurora
  2. 2.UCHSC at Fitzsimmons, Reproductive SciencesAurora
  3. 3.UCHSC at Fitzsimmons, Reproductive SciencesAurora

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