Rabbani Imtiaz, Braun Hannah-Sophie, Akhtar Tasneem, Liebe Franziska, Rosendahl Julia, Grunau Martin, Tietjen Uwe, Masood Saima, Kaessmeyer Sabine, Günzel Dorothee, Rehman Habib, Stumpff Friederike
Department of Physiology, University of Veterinary and Animal Sciences, Lahore, Pakistan.
Institute of Veterinary Physiology, Freie Universität Berlin, Berlin, Germany.
Anim Sci J. 2018 Dec;89(12):1692-1700. doi: 10.1111/asj.13107. Epub 2018 Oct 2.
Absorption of ammonia from the rumen of cattle decreases nitrogen availability for fermentational protein synthesis, leading to increased competition of cattle with humans for protein and enhancing the release of toxic nitrogenous compounds into the environment. Given that differences in feeding and breeding might induce differences in ruminal ammonia transport, we compared electrophysiological, histological, and molecular biological characteristics of ruminal epithelia of Bos indicus crossbreds (Sahiwal-Mix, SWM) with those of Bos taurus (Holstein-Friesian, HF). As in HF, the stratified cornified epithelium of SWM expressed claudin 1 and 4. Measurements of ammonia flux (HF) and serosal pH (both breeds) suggested that at a mucosal pH of 6.4, net transport primarily occurred as NH . As shown previously for HF, NH induced a concentration-dependent rise in short circuit current (I ) in SWM that could be further stimulated by the TRP channel agonist menthol. Relative mRNA expression levels for TRPV3, TRPV4, TRPM6, and TRPM7 were significantly lower in SWM than in HF, with TRPA1 expression near the limit of detection. We conclude that uptake of ammonia from the rumen of both breeds occurs electrogenically as NH with functional and molecular biological evidence pointing towards involvement of TRPV3 and TRPV4.
牛瘤胃中氨的吸收会降低用于发酵性蛋白质合成的氮的可利用性，导致牛与人类对蛋白质的竞争加剧，并增加有毒含氮化合物向环境中的释放。鉴于饲养和繁殖差异可能会引起瘤胃氨转运的差异，我们比较了印度瘤牛杂交种（萨希瓦尔杂交种，SWM）与荷斯坦-弗里生牛（HF）瘤胃上皮的电生理、组织学和分子生物学特征。与HF一样，SWM的复层角质化上皮表达闭合蛋白1和4。氨通量（HF）和浆膜pH值（两个品种）的测量结果表明，在黏膜pH值为6.4时，净转运主要以NH 的形式发生（此处NH可能有误，原文可能是NH₃之类）。如先前对HF的研究所示，NH 在SWM中引起短路电流（I）浓度依赖性升高，该升高可被TRP通道激动剂薄荷醇进一步刺激。SWM中TRPV3、TRPV4、TRPM6和TRPM7的相对mRNA表达水平显著低于HF，TRPA1的表达接近检测极限。我们得出结论，两个品种的瘤胃对氨的摄取均以NH 的形式通过电生成方式发生，功能和分子生物学证据表明TRPV3和TRPV4参与其中。
