FIGURE 5.

Effects of dose and duration of [U-¹³C₃]glycerol administration. A and B show ¹³C NMR spectra of MAG from blood glucose of a fasted (A) or fed (B) rat, and both rats received 100 mg/kg of [U-¹³C₃]glycerol (50%), and blood was drawn at 60 min after the glycerol administration. In fasted rats, the ratio difference between [1,2-¹³C₂]/[2,3-¹³C₂] and [5,6-¹³C₂]/[4,5-¹³C₂] in glucose remained the same statistically over 180 min duration whether they received 50 or 100 mg/kg [U-¹³C₃]glycerol (50%). However, fasted rats had higher ratio difference than fed animals when both groups received the same dose and duration of [U-¹³C₃]glycerol administration (i.e. 100 mg/kg and 60 min; p = 0.004; C). The level of [1,2-¹³C₂]glucose produced through the hepatic PPP (×2 due to 50% tracer) was higher in rats with 100 mg/kg [U-¹³C₃]glycerol (50%) compared with rats with 50 mg/kg. Fasted rats had more [1,2-¹³C₂]glucose produced by the PPP than fed animals (D) (n = 4–6 in each group).