McKenna M C, Bezold L I, Kimatian S J, Tildon J T
Biochem J. 1986 Jul 1;237(1):47-51. doi: 10.1042/bj2370047.
The rate of conversion of [1,3-14C]glycerol into 14CO2 was measured in the presence and absence of unlabelled alternative substrates in whole homogenates from the brains of young (4-6 and 18-20 days old) and adult rats. Unlabelled glucose decreased 14CO2 production from [1,3-14C]glycerol by about 40% at all ages studied. Unlabelled 3-hydroxybutyrate significantly decreased the 14CO2 production from both low (0.2 mM) and high (2.0 mM) concentrations of glycerol in 4-6- and 18-20-day-old rat pups. However, the addition of 3-hydroxybutyrate had no effect on the rate of 14CO2 production from 2.0 mM-glycerol in adult rats, suggesting that the interaction of 3-hydroxybutyrate with glycerol in adult rat brain is complex and may be related to the biphasic kinetics previously reported for glycerol oxidation. Unlabelled glutamine decreased the production of 14CO2 by brain homogenates from 18-20-day-old and adult rats, but not in 4-6-day-old rat pups. In the converse situation, the addition of unlabelled glycerol to whole brain homogenates had little effect on the rate of 14CO2 production from [6-14C]glucose, 3-hydroxy[3-14C]butyrate and [U-14C]glutamine, although some significant differences were noted. Collectively these results suggest that glycerol and these other substrates may be metabolized in separate subcellular compartments in brain such that the products of glucose, 3-hydroxybutyrate and glutamine metabolism can dilute the oxidation of glycerol, but the converse cannot occur. The data also demonstrate that there are complex age-related changes in the interaction of glycerol with 3-hydroxybutyrate and glutamine. The fact that glycerol oxidation was only partially suppressed by the addition of 1-5 mM-glucose, -3-hydroxybutyrate or -glutamine could also suggest that glycerol may be selectively utilized as an energy substrate in some discrete brain region.
在有和没有未标记替代底物的情况下，测定了幼年（4 - 6日龄和18 - 20日龄）和成年大鼠脑全匀浆中[1,3 - 14C]甘油向14CO2的转化速率。在所有研究年龄组中，未标记的葡萄糖使[1,3 - 14C]甘油产生的14CO2减少约40%。未标记的3 - 羟基丁酸显著降低了4 - 6日龄和18 - 20日龄幼鼠低浓度（0.2 mM）和高浓度（2.0 mM）甘油产生的14CO2。然而，添加3 - 羟基丁酸对成年大鼠2.0 mM甘油产生CO2的速率没有影响，这表明成年大鼠脑中3 - 羟基丁酸与甘油的相互作用很复杂，可能与先前报道的甘油氧化的双相动力学有关。未标记的谷氨酰胺降低了18 - 20日龄和成年大鼠脑匀浆中14CO2的产生，但对4 - 6日龄幼鼠没有影响。在相反的情况下，向全脑匀浆中添加未标记的甘油对[6 - 14C]葡萄糖、3 - 羟基[3 - 14C]丁酸和[U - 14C]谷氨酰胺产生14CO2的速率影响很小，尽管也观察到了一些显著差异。总体而言，这些结果表明甘油和这些其他底物可能在脑内不同的亚细胞区室中代谢，使得葡萄糖、3 - 羟基丁酸和谷氨酰胺代谢的产物可以稀释甘油的氧化，但反之则不会发生。数据还表明，甘油与3 - 羟基丁酸和谷氨酰胺的相互作用存在与年龄相关的复杂变化。添加1 - 5 mM葡萄糖、3 - 羟基丁酸或谷氨酰胺仅部分抑制甘油氧化这一事实也可能表明，甘油可能在某些离散的脑区被选择性地用作能量底物。
