|Prapong, Siriwan - IOWA STATE UNIV., AMES|
Submitted to: Federation of American Societies for Experimental Biology Conference
Publication Type: Abstract Only
Publication Acceptance Date: April 16, 2000
Publication Date: N/A
Technical Abstract: Control of transcellular Ca2+ fluxes associated with lactation are critical to mammary function and Ca2+ homeostasis. Control of mammary Ca2+ transport and storage may contribute to the pathological hypocalcemia seen in cows at parturition. We investigated the expression of the secretory pathway Ca2+-ATPase (SPCA), and plasma membrane Ca2+-ATPase isoforms in bovine mammary tissue and on milk fat globule membranes (MFGM). Mammary tissue biopsies were obtained from 13 cows on days -7, 0, +7, +14, with day 0 being calving day. MFGM were prepared from milk samples collected on days 0, +1, +7, and +14 days of lactation. Mammary tissue and MFGM were assayed for Ca2+-ATPase proteins by Western blotting. General PMCA and PMCA4 expression, as detected by 5F10 and NR4, respectively, remained constant in mammary tissue for the experimental period. In contrast, MFGM, PMCA and PMCA4 expression was greatest in membranes from day 1 of lactation and declined significantly by day 14 of lactation. PMCA2 expression in mammary tissue and MFGMs increased throughout the experimental period. SPCA expression in mammary tissue was significant 1 wk prior to parturition and was correlated with the degree of hypocalcemia seen in cows at calving. The varying patterns and amounts of Ca2+-ATPase types expressed in mammary tissue suggest an important role for these Ca2+-ATPases in mammary and cow calcium homeostasis. The most striking finding is that the SPCA expression 1 wk prior to parturition correlated with hypocalcemia seen at parturition.