Elsasser Ted H, Capuco Anthony V, Caperna Thomas J, Martínez Alfredo, Cuttitta Frank, Kahl Stanislaw
USDA-ARS, Growth Biology Laboratory, Beltsville, MD 20705, US.
Domest Anim Endocrinol. 2007 Feb;32(2):138-54. doi: 10.1016/j.domaniend.2006.02.004. Epub 2006 Mar 13.
Adrenomedullin (AM) has been characterized as an endogenous tissue survival factor and modulator of many inflammatory processes. Because of the increased susceptibility of the mammary gland to infection during the time surrounding parturition in the cow, we investigated how milk and tissue content of AM and its binding protein (AM-BP) might be affected by the stage of lactation and the udder health status. Milk and mammary biopsy samples were obtained from Holstein cows 21 days prior to and at various times after calving to represent the dry period and early and mid-stages of lactation. Additional cows received an intramammary challenge with Escherichia coli for immunohistochemical characterization of AM and AM-BP. Milk AM concentrations were relatively constant across the stages of lactation while AM-BP increased two-fold (P<0.04) between early and mid-lactation. Milk AM (P<0.04) and AM-BP (P<0.03) increased as somatic cell counts (SCCs) increased within a given stage of lactation. Tissue content of both (AM and AM-BP) were significantly affected by stage of lactation, lowest in the dry period and progressively increasing to peak at mid-lactation as well as increasing in association with higher levels of SCCs. Following E. coli challenge, AM increased in epithelial cells surrounding mammary alveoli presenting high levels of SCCs. The data suggest that AM and AM-BP are cooperatively regulated in the mammary gland during lactation; changes in localized tissue AM and AM-BP content reflect a dynamic regulation of these tissue factors in the bovine mammary gland consistent with their protective effects within inflamed tissue.
肾上腺髓质素（AM）已被确定为一种内源性组织存活因子和多种炎症过程的调节剂。由于奶牛在分娩前后乳腺对感染的易感性增加，我们研究了AM及其结合蛋白（AM-BP）的乳汁和组织含量如何受到泌乳阶段和乳房健康状况的影响。在产犊前21天以及产犊后的不同时间从荷斯坦奶牛获取乳汁和乳腺活检样本，以代表干奶期、泌乳早期和中期。另外的奶牛接受大肠杆菌乳房内攻毒，用于对AM和AM-BP进行免疫组织化学特征分析。乳汁中AM浓度在泌乳各阶段相对恒定，而AM-BP在泌乳早期和中期之间增加了两倍（P<0.04）。在泌乳的给定阶段内，随着体细胞计数（SCC）增加，乳汁中的AM（P<0.04）和AM-BP（P<0.03）也增加。（AM和AM-BP的）组织含量均受到泌乳阶段的显著影响，在干奶期最低，在泌乳中期逐渐增加至峰值，并且随着SCC水平升高而增加。在大肠杆菌攻毒后，AM在呈现高水平SCC的乳腺腺泡周围的上皮细胞中增加。数据表明，泌乳期间AM和AM-BP在乳腺中受到协同调节；局部组织中AM和AM-BP含量的变化反映了这些组织因子在牛乳腺中的动态调节，这与其在炎症组织中的保护作用一致。
