Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 20, 2004
Publication Date: May 20, 2004
Citation: Reinhardt, T.A. 2004. Calcium pumps and calcium transport in the mammary gland. Meeting Abstract. Technical Abstract: The requirements for calcium transport through the mammary gland and into milk are enormous. This mammary calcium transport is believed to be centered on calcium uptake by the Golgi to provide the bulk of calcium that enters milk. Recent work has identified the calcium pumps expressed in the lactating mammary gland. PMCA1b, PMCA4b, SERCA2, and SERCA3 are upregulated during lactation but their expression is significantly less than that of PMCA2bw or SPCA1. SPCA1 is the only calcium pump to increase its expression just prior to parturition and the initiation of lactation. SPCA1 expression continues to increase with milk production and has been shown by us and others to be a Golgi resident Ca2+ATPase. Therefore, SPCA1 is a candidate pump for primary control of milk calcium. It must be pointed out that PMCA2bw is the most abundant pump found in lactating tissue and its expression most closely mirrors milk production. PMCA2bw is found on the apical membrane of secretory cells and is secreted into the milk as a part of the MFGM. PMCA2bw abundance and expression pattern raised questions about its role in mammary calcium transport. Using PMCA2 knockout mice, we have shown that knockout mice make milk with similar protein and lactose concentrations to that of wild type mice. Milk calcium is reduced by 60% in knockouts compared to wild type mice. These data suggest that PMCA2 is a primary regulatory of milk calcium and raises questions about the cellular location of this pump in the mammary gland.