During mammalian reproduction, including that of humans, large amounts of calcium are transferred from mother to offspring through breast milk. Subsequently, adaptive mechanisms are required to maintain a healthy balance of calcium in the mother's body. These involve the breakdown of calcium stores in bone and increased dietary calcium intake in order to maintain a steady supply of calcium to the breast for purposes of milk production. The factors involved in the regulation of calcium stores are largely unknown.
The calcium-sensing receptor (CaR) is known to regulate how our cells respond to fluctuations in extracellular calcium levels. A report from John Wysolmerski and colleagues from Yale University in the February 16 issue of the Journal of Clinical Investigation reveals that in mice, at the transition from pregnancy to lactation, expression of CaR on mammary epithelial cells is upregulated. Dietary restriction of calcium upregulated parathyroid hormone-related protein production during lactation, decreased the calcium content of milk, increased milk osmolality and protein concentration, and decreased overall milk production. Most of these effects were prevented by the infusion of calcimimetic compounds, implicating CaR as the key mediator of these processes. This indicates that the lactating mammary gland can sense calcium increases and losses and adjusts its secretion of calcium accordingly. This helps match milk production with the availability of calcium in the mother's body.
TITLE: The calcium-sensing receptor regulates mammary gland parathyroid hormonerelated protein production and calcium transport
John J. Wysolmerski
Yale University School of Medicine, New Haven, Connecticut, USA.
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