Radiorespirometric study of glucose metabolism in liver-damaged rats

Changes in glucose metabolism in rats during feeding with 3-methyl-4-(dimethylamino)azobenzene (3'-Me-DAB) were investigated by radiorespirometry with 14C-labelled carbohydrates as substrates, in relation to the levels of liver glycolytic enzyme activities. Rats were fed on 0.06% 3'-Me-DAB for 7 weeks. Radiorespirometry was carried out by the IP administration of [U-14C] glucose 2.5 micro Ci or [1-14C] acetate 2.0 micro Ci weekly during the experimental period. In the analysis of the radiorespirometric pattern obtained with [U-14C]glucose, the peak time (PT) was markedly shortened at week 4. At week 6 of 3'-Me-DAB feeding, the peak height (PH) and yield value (YV) both increased significantly with concomitant shortening of PT. The duration of the activation in radiorespirometric parameters was paralleled reasonably well by that of glycolytic enzyme activity; the activation of liver glucose-6-phosphate dehydrogenase (G-6-PDH) shortens PT, while the activation of the tricarboxylic acid (TCA) cycle increases YV. This study showed that the radiorespirometric pattern reflected glucose metabolism in the liver well. In conclusion, radiorespirometric analysis with 14C-labelled glucose as a substrate may be useful for the clinical diagnosis of liver diseases.