An Essential Protein That Pumps Calcium Into Breastmilk

A study in mice has revealed that the protein Orai1 is responsible for 50 percent of the calcium ions in a mother’s milk.

AsianScientist (May 13, 2015) – Research at the University of Queensland (UQ) has unlocked a mysterious process essential to breastfeeding: how calcium is transferred into mother’s milk. The study documenting these findings has been published in the Proceedings of the National Academy of Sciences.

The team led by UQ’s School of Pharmacy trio Dr. Felicity Davis, Professor Gregory Monteith and Professor Sarah Roberts-Thomson demonstrated that a store-operated calcium (Ca2+) channel subunit, Orai1, is required for both optimal Ca2+ transport into milk and for milk ejection, at least in mice.

By using a three-dimensional imaging strategy and visualizing live oxytocin-induced alveolar unit contractions in the mammary gland, the researchers were able to show that milk is ejected by way of pulsatile contractions of these alveolar units.

“Using rodent models, we have demonstrated that at least 50 percent of calcium ions in a mother’s milk comes from one specific protein called Orai1,” said Davis, a UQ National Health and Medical Research Council early career research fellow.

Oxytocin, a naturally-produced chemical, is attributed to the building of mother-offspring bonds. Breastfeeding results in the increase of oxytocin production and oxytocin-induced contractions in the mammary gland, as observed by the researchers.

Oxytocin also induces a large transient release of stored Ca2+ in mammary myoepithelial cells followed by slow, irregular Ca2+ oscillations. These oscillations, not the initial Ca2+ transient, are mediated exclusively by Orai1 and are essential for milk ejection and pup survival, an observation that redefines the signaling processes responsible for milk ejection.

“There’s also an unanticipated revelation that Orai1 is a master regulator of milk ejection and pivotal to the survival of mammalian young,” said Davis, who is currently based at the University of Cambridge.

Davis notes that their discovery could add to the understanding of processes that are related to breast cancer. It could also have future implications for cancer treatment.

“Inadvertently, a better understanding of mammary gland biology and lactation will help us identify processes that may be important in some breast cancers.”

The article can be found at: Davis et al. (2015) Essential Role Of Orai1 Store-operated Calcium Channels In Lactation.


Source: The University of Queensland; Photo: Shutterstock.
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