Spires H R, Clark J H
J Nutr. 1979 Aug;109(8):1438-47. doi: 10.1093/jn/109.8.1438.
Isotope dilution techniques were used to study steady-state glucose kinetics in four rumen-fistulated Holstein steers and to study the effect of rapid absorption of ammonia from the rumen on glucose metabolism. Steers were fed a high-concentrate diet at hourly intervals from automatic feeders. Plasma glucose specific activity curves following single intravenous injection of [2-3H]glucose were used to construct a two-compartment model of the glucose pool with inflow and outflow from compartment one. Primed continuous infusion of [2-3H]glucose was used to determine the steady-state turnover rate of glucose and to monitor changes in the rates of inflow and outflow of glucose from the glucose pool following a single dosage of urea (0.4 g/kg body weight) into the rumen. Compartment sizes of the glucose pool were 65.6 and 33.5 g for compartments 1 and 2, respectively. Glucose turnover rate during steady-state was 15.4 mg/minute/kg body weight 0.75 and transfer rate of glucose between compartments was 17.9 mg/minute/kg body weight 0.75. Concentrations of rumen ammonia-nitrogen, plasma ammonia-nitrogen and plasma urea-nitrogen were 6.1, 0.5 and 4.0 mg/100 ml, respectively, before urea dosage. Rumen ammonia-nitrogen, plasma ammonia-nitrogen increased after urea dosage and reached peak concentrations, 170.0 and 1.2 mg/100 ml, respectively, approximately 120 minutes after urea dosage. Plasma urea-nitrogen increased linearly throughout the 4-hour sampling period and reached 12.0 mg/100 ml at end of the experiment. Concentration of glucose in plasma increased from 98.2 mg/100 ml before urea dosage to 114.6 mg/100 ml at 100 minutes after urea dosage. Estimates of glucose production and utilization indicated that the increased concentration of glucose in plasma in all steers was due, at least partially, to a decrease in the rate of glucose utilization. A rapid rate of glycogenolysis which resulted in a marked increase in the plasma glucose concentration also was evident in one steer.
采用同位素稀释技术研究了四头瘤胃造瘘的荷斯坦阉牛的稳态葡萄糖动力学，并研究了瘤胃中氨的快速吸收对葡萄糖代谢的影响。每隔一小时从自动喂料器给阉牛投喂高浓缩日粮。单次静脉注射[2-³H]葡萄糖后，根据血浆葡萄糖比活度曲线构建了一个葡萄糖池的两室模型，葡萄糖从一室流入和流出。通过[2-³H]葡萄糖的预充连续输注来确定葡萄糖的稳态周转率，并监测向瘤胃单次投服尿素（0.4 g/kg体重）后葡萄糖池的葡萄糖流入和流出速率的变化。葡萄糖池的一室和二室大小分别为65.6克和33.5克。稳态期间葡萄糖周转率为15.4毫克/分钟/千克体重0.75，两室之间的葡萄糖转移速率为17.9毫克/分钟/千克体重0.75。投服尿素前，瘤胃氨氮、血浆氨氮和血浆尿素氮浓度分别为6.1、0.5和4.0毫克/100毫升。投服尿素后，瘤胃氨氮和血浆氨氮增加，并分别在投服尿素后约120分钟达到峰值浓度170.0和1.2毫克/100毫升。在整个4小时的采样期内，血浆尿素氮呈线性增加，实验结束时达到12.0毫克/100毫升。血浆葡萄糖浓度从投服尿素前的98.2毫克/100毫升增加到投服尿素后100分钟时的114.6毫克/100毫升。葡萄糖生成和利用的估计表明，所有阉牛血浆中葡萄糖浓度的升高至少部分是由于葡萄糖利用率的降低。在一头阉牛中还明显出现了快速的糖原分解速率，这导致血浆葡萄糖浓度显著升高。
