|Reinhardt, Timothy - Tim|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/17/2005
Publication Date: 5/20/2005
Citation: Prapong, S., Reinhardt, T.A., Goff, J.P., Horst, R.L. 2005. Ca2+-adenosine triphosphatase protein expression in the mammary gland of periparturient cows. Journal of Dairy Science. 88(5):1741-1744. Interpretive Summary: Most metabolic and infectious diseases in dairy cows are problems whose genesis starts with the stresses of the initiation of lactation. Calcium flows rapidly into the mammary gland, prior to the start of lactation, into as yet unidentified storage sites. The rapidity of this calcium loss contributes to milk fever and the complications that result from milk fever and subclinical hypocalcemia. Fine control of mammary milk cell calcium also is key to the health, hormone responsiveness and the quality of milk produced by the cow. The well-being of the cow and her profitability could be greatly enhanced by understanding those factors that regulate the mammary glands transition to milk production and the concomitant excretion of calcium. This paper represents the fifth in a series of studies examining factors controlling calcium flow and storage in the mammary at and around calving. We have previously studied the synthesis of 4 calcium pumps in the milk-producing mammary gland. All pumps increased when lactation started, but one pump increased prior to the start of milk production. Two pumps stand out as candidates for controlling most of the calcium movement in the mammary gland and thus the hypocalcemia (milk fever) that causes a disease complex in the transition cow. Their scientific names are plasma membrane calcium ATPase 2bw and the secretory pathway calcium ATPase (SPCA1). This paper demonstrates that SPCA1 is expressed at a significantly higher level in milk fever cows than in non-milk fever cows. This pump is responsible for mammary Golgi calcium storage and thus its higher expression in milk fever cows suggests that its expression is a major contributor to the development of milk fever in dairy cows. Results of this study will benefit the dairy industry worldwide.
Technical Abstract: The objectives of this study were to measure the changes in protein expression of the mammary Ca2+-ATPases during the periparturient period and to determine if Ca2+-ATPase protein expression in the mammary gland is related to milk fever development. Ca2+-ATPase abundance in mammary tissue and milk fat globule membranes was determined by Western blotting. The secretory pathway Ca2+-ATPase was elevated prepartum in mammary tissue from cows that developed milk fever compared to non-milk fever cows.