Brain glucose utilization in undernourished rats.

The in vivo incorporation of radioactivity from [U-14C]glucose was reduced in undernourished rat pups at ages 6, 10, and 17 days for brain lipids, and at age 10 days for brain amino acids. Brain glucose concentrations were lower at age 20 days (controls 1.58 +/- 0.26 vs. test 1.14 +/- 0.07 mumol/g) but other alterations in brain glucose, glycogen, ATP, or phosphocreatine concentrations were not found. Brain mitochondrial glutamate dehydrogenase activity was 21% and 30% lower in undernourished animals at ages 10 and 20 days, respectively. Brain mitochondrial and supernatant isocitrate dehydrogenase activities and pyruvate kinase activity were similar for undernourished and control animals. Brain glycogen levels were 2-4 times higher in late fetal and newborn control animals (13.6 and 15.3 mumol/g) than in older animals (4.2-5.7 mumol/g). Brain glucose, ATP, and phosphocreatine levels increased from the 15-day fetus to the newborn, but thereafter showed no further increase.