In vivo assessment of metabolic perturbations following alanine and glucagon administration using 31P-MRS in the rat.
This study set out to validate the use of 31P-NMR spectroscopy together with alanine +/- glucagon infusions to assess hepatic gluconeogenic flux in vivo. Bolus infusions of alanine (2.8 or 5.6 mmol/kg) +/- glucagon (250 microg/kg) were used. Maximal changes in the phosphomonoesters (PME), inorganic phosphate (Pi) and beta-NTP occurred 40 mins post infusion. PME increased 13.1% (p < 0.02) and 20.8% (P < 0.01) at 2.8 mmol/kg + glucagon and 5.6 mmol/kg +/- glucagon, respectively. Pi 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 infusion showed slower recovery rates of NTP which remained 12.3% (P < 0.05) lower 70 min post infusion compared with pre-infusion values. 31 P-NMR analysis of liver extracts revealed that PME increases were partly 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 showed no difference between alanine concentrations indicating maximal glucose output at the lower concentration. This study has shown that in vivo 31P-NMR in combination with alanine infusion, can be used to determine metabolic changes associated with gluconeogenesis.
Changani
K K
KK
Cellular Mechanisms Research Group, Medical Unit, London Hospital Medical College, Whitechapel, UK.
Barnard
M L
ML
Bell
J D
JD
Thomas
E L
EL
Williams
S C
SC
Bloom
S R
SR
Iles
R A
RA
D000409:Alanine / Q000008:administration & dosage / Q000378:metabolism*; D000818:Animals; D005934:Glucagon / Q000008:administration & dosage / Q000378:metabolism*; D005943:Gluconeogenesis; D005947:Glucose / Q000032:analysis; D008099:Liver / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D008297:Male; D010477:Perfusion; D010710:Phosphates / Q000032:analysis; D010759:Phosphorus Isotopes; D051381:Rats; D017208:Rats, Wistar
D010710:Phosphates; D010759:Phosphorus Isotopes; D005934:Glucagon; D005947:Glucose; D000409:Alanine