IN-VIVO ASSESSMENT OF METABOLIC PERTURBATIONS FOLLOWING ALANINE AND GLUCAGON ADMINISTRATION USING P-31-MRS IN THE RAT

This study set out to validate the use of P-31-NMR spectroscopy togeth er with alanine +/- glucagon infusions to assess hepatic gluconeogenic flux in vivo. Bolus infusions of alanine (2.8 or 5.6 mmol/kg) +/- glu cagon (250 mu g/kg) were used. Maximal changes in the phosphomonoester s (PME), inorganic phosphate (P-i) and beta-NTP occurred 40 mins post infusion. PME increased 13.1% (p < 0.02) and 20.8% (P < 0.01) at 2.8 m mol/kg + glucagon and 5.6 mmol/kg +/- glucagon, respectively. P-i was unaltered at 2.8 mmol/kg but increased by 28.8% (P < 0.01) at 5.6 mmol /kg alanine + glucagon, beta-NTP decreased by 14.4% (P < 0.02) and 16. 1% (P < 0.02) at 5.6 mmol/kg -/+ glucagon, respectively. This latter i nfusion showed slower recovery rates of NTP which remained 12.3% (P < 0.05) lower 70 min post infusion compared with pre-infusion values, P- 31-NMR analysis of liver extracts revealed that PME increases were par tly due to 3-phosphoglycerate and corroborated reductions in beta-NTP and gamma-NTP: beta-NDP ratio upon infusion of 5.6 mmol/kg alanine +/- glucagon. Hepatic glucose output from perfused liver experiments show ed no difference between alanine concentrations indicating maximal glu cose output at the lower concentration. This study has shown that in v ivo P-31-NMR in combination with alanine infusion, can be used to dete rmine metabolic changes associated with gluconeogenesis.