ABSTRACT This paper aims to study the effect of the dietary treatments on mRNA expression of urea transporter B (UT-B) and some aquaporins (AQP) in rumen epithelium of Italian Simmental young bulls. Eighty animals allocated to 16 pens were fed from about 500 to 650 kg body weight with four experimental diets, which resulted from the combination of two crude protein levels (125 and 110 g/kg dry matter, diets M and L, respectively) and two nitrogen sources (soybean meal (SBM) or SBM partly replaced by an isonitrogenous mixture of corn and urea; diets −U and +U, respectively). At slaughtering samples of blood and rumen epithelium were collected from six bulls for each diet. Blood samples were analysed for haematological parameters and quantitative PCR was carried out on the mRNA extracted from the rumen epithelium samples. The bulls fed diets M had lower plasma concentrations of aspartate aminotransferase than those receiving diets L (78.9 vs. 88.3 U/l, p = 0.04). Plasma urea was higher (p = 0.03) for diets M and lower for diets +U (2.0 vs. 2.5 and 1.73 vs. 2.00 mmol/l, respectively, in M and L diets, p = 0.04). The effect of dietary treatments on rumen UT expression were limited to AQP3, which was down regulated (p = 0.01) in diets +U. Finally, a high positive correlation (R2 = 0.871) between the expressions of AQP7 and AQP10 was found. In conclusion, the AQP3 appears very responsive to dietary treatments and therefore it is a candidate to be further studied in rumen metabolism experiments. The close relationship between mRNA expression of AQP7 and AQP10 indicates a similar function of these two proteins.

中文翻译：

---

日粮氮水平和来源对育肥公牛瘤胃上皮尿素转运蛋白mRNA表达的影响

摘要 本文旨在研究日粮处理对意大利西门塔尔公牛瘤胃上皮中尿素转运蛋白 B (UT-B) 和部分水通道蛋白 (AQP) mRNA 表达的影响。分配到 16 个围栏的 80 只动物用四种实验日粮喂养体重约 500 至 650 公斤，这是由两种粗蛋白水平（分别为 125 和 110 克/公斤干物质，日粮 M 和 L）和两种氮源（豆粕 (SBM) 或 SBM 部分被玉米和尿素的等氮混合物替代；分别为 -U 和 +U 日粮）。在屠宰时，每种饮食从六头公牛中收集血液和瘤胃上皮样品。分析血液样品的血液学参数，并对从瘤胃上皮样品中提取的 mRNA 进行定量 PCR。饲喂日粮 M 的公牛的血浆天冬氨酸转氨酶浓度低于接受日粮 L 的公牛（78.9 对 88.3 U/l，p = 0.04）。饮食 M 的血浆尿素较高 (p = 0.03)，而饮食 +U 的血浆尿素较低（M 和 L 饮食分别为 2.0 对 2.5 和 1.73 对 2.00 mmol/l，p = 0.04）。饮食处理对瘤胃 UT 表达的影响仅限于 AQP3，其在饮食 +U 中下调（p = 0.01）。最后，发现 AQP7 和 AQP10 的表达之间存在高度正相关（R2 = 0.871）。总之，AQP3 似乎对饮食处理非常敏感，因此它是瘤胃代谢实验中进一步研究的候选者。AQP7 和 AQP10 的 mRNA 表达之间的密切关系表明这两种蛋白质的功能相似。