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首页> 外文期刊>Life sciences >Stress down regulates milk yield in cows by plasmin induced beta-casein product that blocks K+ channels on the apical membranes
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Stress down regulates milk yield in cows by plasmin induced beta-casein product that blocks K+ channels on the apical membranes

机译：纤维蛋白溶酶诱导的β-酪蛋白产物阻断了顶端膜上的K +通道，从而降低了奶牛的产奶量

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摘要

Stress and stress related hormones such as glucocorticoids inhibit lactation in cows. In the present study we propose a novel mechanism connecting stress with plasminogen-plasmin system (PPS) (an enzymatic mechanism in milk, which leads to the breakdown of the major milk protein casein). We show that stress activates the PPS leading to an increase in plasmin activity, and that a distinct plas min-induced beta-casein breakdown product (fraction 1-28) is a potent blocker of potassium channels in mammary epithelia apical membranes. The reduction in milk production due to dehydration stress or glucocorticoid (dexamethsone) was correlated with the activities of plasmin and channel blocking activity in the milk of the tested cows. The notion that the axis Stress-PPS-beta-casein fraction 1-28 is responsible fur the reduction in milk yield is supported by the results of experiments showing that injecting solution composed of casein digest enriched with beta-casein fraction 1-28 to the udder lumen leads to a transient reduction in milk production. Furthermore, injecting a pure beta-casein fraction 1-28 to the udder lumen of goat's lead also to a transient reduction in milk production with kinetics that was similar to the kinetics observed in cows. (C) 2000 Elsevier Science Inc. All rights reserved. [References: 29]
机译：压力和与压力有关的激素（如糖皮质激素）会抑制母牛的泌乳。在本研究中，我们提出了一种将压力与纤溶酶原-纤溶酶系统（PPS）连接的新机制（牛奶中的一种酶促机制，导致主要的酪蛋白酪蛋白分解）。我们表明，压力激活PPS，导致纤溶酶活性增加，并且独特的plas min诱导的β-酪蛋白分解产物（馏分1-28）是乳腺上皮顶膜中钾通道的有效阻断剂。由于脱水应激或糖皮质激素（地塞米松）而导致的产奶量减少与被测母牛的牛奶中的纤溶酶活性和通道阻断活性有关。实验结果表明，应力-PPS​​-β-酪蛋白馏分1-28负责降低牛奶产量的观点得到了支持，该实验结果表明，将富含β-酪蛋白馏分1-28的酪蛋白消化液组成的溶液注入乳房内腔导致牛奶产量的短暂减少。此外，将纯β-酪蛋白级分1-28注射到山羊铅的乳房内腔中，也会导致牛奶产量的瞬时降低，其动力学与在母牛身上观察到的动力学相似。 （C）2000 Elsevier Science Inc.保留所有权利。 [参考：29]

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