Dynamic monitoring of corneal carbohydrate metabolism using high-resolution deuterium NMR spectroscopy.

Glucose metabolism in rabbit corneas was monitored with deuterium (D or 2H) NMR spectroscopy. The corneas were incubated in 5.5 mM deuterated glucose (glucose-6, 6-D2). A 2.5 micrograms change in lactate and a 4.1 micrograms change in glucose could be detected by the NMR method. The mean rates of glucose utilization and lactate production in intact rabbit corneas were 248- and 151 micrograms h-1, respectively. The lactate production/glucose utilization ratio of 0.60, i.e. 60% of total glucose is metabolized to lactate, confirms that glycolysis is the principal pathway for glucose catabolism. Further, based on enrichment of the HDO signal (which refers to the naturally abundant deuterium signal arising from deuterons in water), glucose oxidation through Krebs cycle and its associated pathways is estimated to be 90 micrograms h-1 or 36% of total consumption. The significant advantages of deuterium NMR spectroscopy over other NMR techniques (e.g. 13C spectroscopy) are: (1) shorter acquisition times because of the short relaxation times of deuterated metabolites; (2) the HDO signal can be used as the internal reference; and (3) significant reduction in cost and high availability of 2H-labeled compounds. Deuterium NMR spectroscopy is therefore a reliable and effective means with which the corneal glycolytic activity prior to transplantation can be readily assessed.