Dunn A, Katz J, Golden S, Chenoweth M
Am J Physiol. 1976 Apr;230(4):1159-62. doi: 10.1152/ajplegacy.1976.230.4.1159.
The glucose replacement rate, percent carbon recycling, mean glucose transit time, and the glucose mass were determined in fasted unanesthetized rabbits after administration of [2-3H,U-14C]-, [3-3H,U-14C]-, [5-3H,U-14C]- or [6-3H,U-14C]glucose using the procedures of Katz et al. (10). The glucose replacement rates and carbon recycling determined with [2-3H,U-14C] and [5-3H,U-14C]glucose are equivalent and greater than those obtained with [3-3H,U-14C]- and [6-3H,U-14C]glucose. Although the means of the glucose replacement rates and percent carbon recycling obtained using [3-3H,U-14C]- and [6-3H,U-14C]glucose are similar, greater variation resulted using the former tracer. Comparisons of detritiation rates and percent carbon recycling using [2-3H,U-14C]- and [6-3H,U-14C]glucose suggest that about 10% of tritium is lost from carbon 2 via futile cycling at the glucose 6-phosphate level. Similarly, comparisons of [5-3H,U-14C]- and [6-3H,U-14C]glucose metabolism suggest that about 10% of tritium lost from carbon 5 occurs via futile cycling at the fructose diphosphate level and/or via the transaldolase reaction. Our results indicate that [6-3H,U-14C]glucose is the more suitable tracer for determining the glucose replacement rate and carbon recycling in vivo.
采用Katz等人（文献10）的方法，在禁食且未麻醉的兔子给药[2-³H，U-¹⁴C]-、[3-³H，U-¹⁴C]-、[5-³H，U-¹⁴C]-或[6-³H，U-¹⁴C]葡萄糖后，测定葡萄糖替代率、碳循环百分比、平均葡萄糖转运时间和葡萄糖量。用[2-³H，U-¹⁴C]和[5-³H，U-¹⁴C]葡萄糖测定的葡萄糖替代率和碳循环量相当，且高于用[3-³H，U-¹⁴C]-和[6-³H，U-¹⁴C]葡萄糖获得的结果。虽然用[3-³H，U-¹⁴C]-和[6-³H，U-¹⁴C]葡萄糖获得的葡萄糖替代率和碳循环百分比的均值相似，但使用前一种示踪剂时变异更大。用[2-³H，U-¹⁴C]-和[6-³H，U-¹⁴C]葡萄糖比较脱氚率和碳循环百分比表明，约10%的氚在葡萄糖6-磷酸水平通过无效循环从碳2丢失。同样，比较[5-³H，U-¹⁴C]-和[6-³H，U-¹⁴C]葡萄糖代谢表明，从碳5丢失的约10%的氚是在果糖二磷酸水平通过无效循环和/或通过转醛醇酶反应发生的。我们的结果表明，[6-³H，U-¹⁴C]葡萄糖是体内测定葡萄糖替代率和碳循环更合适的示踪剂。
