Moussaoui F, Michelutti I, Le Roux Y, Laurent F
Unité sous contrat avec l'Institut National de la Recherche Agronomique, Ecole Nationale Supérieure d'Agronomie et des Industries Alimentaires, Vandoeuvre-lés-Nancy, France.
J Dairy Sci. 2002 Oct;85(10):2562-70. doi: 10.3168/jds.S0022-0302(02)74339-7.
Experimental mastitis has been induced by the lipopolysaccharide (LPS) of Escherichia coli on six dairy cows in order to study the mechanisms involved in milk endogenous proteolysis during the inflammatory process. Variations in somatic cell count (SCC), plasmin activity, and total casein (CN) content were measured, and proteose-peptone content and the percentage of pH 4.6 insoluble peptides including gamma-CN have been considered as indicators of endogenous proteolysis. Furthermore, polymorphonuclear neutrophils (PMN) maturity has been evaluated by optical microscopy, and proteolysis by PMN proteinases has been studied at neutral and acidic pH in order to establish a link between caseinolysis, proteinase class, and PMN maturation. Two peaks of proteose-peptones content have been noticed for the six cows. First peak could be explained by both plasmin activity and SCC, while second peak was concomitant with a low plasmin activity but a SCC remaining high. The second peak of proteose-peptones content confirmed the role of cellular proteases in milk caseinolysis. Casein breakdown by cellular proteases was confirmed by SDS-PAGE electrophoresis, and a link between neutral proteinases activity and immature PMN recruitment was shown. Acidic proteinases activity was effective with mature PMN and during the recovery phase.
为了研究炎症过程中牛奶内源性蛋白水解的相关机制，已通过大肠杆菌的脂多糖（LPS）诱导六头奶牛发生实验性乳腺炎。测量了体细胞计数（SCC）、纤溶酶活性和总酪蛋白（CN）含量的变化，并将蛋白胨含量以及包括γ-酪蛋白在内的pH 4.6不溶性肽的百分比作为内源性蛋白水解的指标。此外，通过光学显微镜评估了多形核中性粒细胞（PMN）的成熟度，并研究了中性和酸性pH条件下PMN蛋白酶的蛋白水解作用，以建立酪蛋白水解作用、蛋白酶类别与PMN成熟度之间的联系。六头奶牛均出现了两个蛋白胨含量峰值。第一个峰值可由纤溶酶活性和SCC共同解释，而第二个峰值则与低纤溶酶活性但SCC仍保持高位同时出现。蛋白胨含量的第二个峰值证实了细胞蛋白酶在牛奶酪蛋白水解中的作用。通过SDS-PAGE电泳证实了细胞蛋白酶对酪蛋白的分解作用，并显示了中性蛋白酶活性与未成熟PMN募集之间的联系。酸性蛋白酶活性在成熟PMN以及恢复阶段发挥作用。
