Use of 2H2O to study labeling in plasma glucose and hepatic glycogen during a hyperglycemic clamp.
In this study, we demonstrate the use of 2H2O, in a manner analogous to 3H2O, to study gluconeogenic flux (deuterium labeling at the carbon-6 position of glucose) relative to overall flux through glucose 6-phosphate (deuterium labeling at the carbon-2 position of glucose) into glucose output and glycogen synthesis during hyperglycemia. Before the study (4 days), jugular and carotid catheters were placed. Rats were fasted for 17 h before the study. 2H2O was infused for 2 h at 3 ml/h, with a subsequent 1-h equilibration period. A hyperglycemic clamp at 180 mg/dl (10 mM) was then performed for 90 min (plasma samples obtained at 10-min intervals). At the end of the experiment, anesthesia was induced and the liver removed. Gas chromatography-mass spectroscopy isotopomer analysis of four different mass clusters from glucose was used to determine deuterium enrichment on the carbon-2 (E2D) and carbon-6 (E6D) positions of plasma glucose and glycogen-glucose. The results show that the labeling pattern in glycogen and plasma glucose was virtually identical. In addition, the E6D-to-E2D ratio in plasma glucose did not change during hyperglycemia. Additional studies were performed to show that the E6D-to-E2D ratio was decreased in the fed state and that the fed animal, compared with the fasted rat, had a marked increase in the ratio when given an epinephrine infusion. Thus it was concluded that this was a robust new technique for analyzing glucose and glycogen metabolism in rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Shalwitz
R A
RA
Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri.
Beth
T J
TJ
MacLeod
A M
AM
Tucker
S J
SJ
Rolison
G G
GG
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism*; D017666:Deuterium Oxide; D004837:Epinephrine / Q000494:pharmacology; D005215:Fasting; D008401:Gas Chromatography-Mass Spectrometry; D015309:Glucose Clamp Technique; D006003:Glycogen / Q000378:metabolism*; D006706:Homeostasis; D008099:Liver / Q000378:metabolism*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley
D001786:Blood Glucose; D006003:Glycogen; D017666:Deuterium Oxide; D004837:Epinephrine