Szanyiová M, Bod'a K, Bazanova N V, Tasenov K T, Karinbaev R S, Leng L, Makasev E K
Vet Med (Praha). 1985 Feb;30(2):83-90.
Urea excretion was studied in an experiment with two sheep breeds (steppe fat-tailed and merino) on the second day of fasting when the urea concentration in blood increases in fasting animals. The control group in the two breeds was given free-choice feed and water while fasting sheep were given ad libitum only water. Diuresis in both breeds was steady during the experiment. Glomerular filtration rate was not found to vary, in comparison with the control, although the plasma urea concentration rose in fat-tailed sheep (P less than 0.01) as well as in the sheep of merino breed (P less than 0.001). Fractional excretion of urea decreased in fat-tailed sheep (P less than 0.05) and also in the sheep of merino breed (P less than 0.02) while total output of urea remained steady in fat-tailed sheep but it increased in merino sheep (P less than 0.02). Tubular reabsorption of urea on the second day of fasting was observed to be higher by 65% in merino sheep (P less than 0.001), but in steppe fat-tailed sheep the increase was much higher--by up to 180% (P less than 0.001), in comparison with the control. It was demonstrated by the results that the increased tubular reabsorption of urea contributes to the rise of plasma urea concentration in sheep on the second day of fasting.
在一项针对两个绵羊品种（草原肥尾羊和美利奴羊）的实验中，研究了禁食第二天的尿素排泄情况，此时禁食动物的血液尿素浓度会升高。两个品种的对照组在禁食期间可自由采食和饮水，而禁食的绵羊仅随意给予水。在实验过程中，两个品种的利尿情况均保持稳定。与对照组相比，未发现肾小球滤过率有变化，尽管肥尾羊（P<0.01）和美利奴羊（P<0.001）的血浆尿素浓度均有所升高。肥尾羊（P<0.05）和美利奴羊（P<0.02）的尿素排泄分数均下降，而肥尾羊的尿素总排出量保持稳定，但美利奴羊的尿素总排出量增加（P<0.02）。观察到禁食第二天美利奴羊的尿素肾小管重吸收比对照组高65%（P<0.001），但草原肥尾羊的增加幅度更大——高达180%（P<0.001）。结果表明，禁食第二天绵羊肾小管对尿素重吸收的增加导致了血浆尿素浓度的升高。
