Direct pathway for hepatic glycogenesis predominates in meal-fed rats
The pathway for hepatic glycogen synthesis in the postprandial state was studied in meal-fed rats chronically cannulated in the portal vein. The rate of glycogen synthesis in livers of rats meal-fed for seven days was found to be about 1 umol/g/min. Plasma glucose concentration in the portal vein was generally below 8 mM before meal-feeding and could reach up to 12 mM at the end of the meal-feeding. Studies on the hepatic-portal (H-P) difference of plasma glucose showed that liver released glucose in the fasted state and could either extract or release glucose after feeding, depending on plasma glucose concentration in the portal vein. The cross-over concentration for the transition was found to be 8 mM. The relative importance of the direct vs indirect pathway for the replenishment of hepatic glycogen was determined by injecting (3-/sup 3/H,U-/sup 14/C)-glucose into the portal vein at the end of meal-feeding. Six minutes after the injection, the ratio of /sup 3/H//sup 14/C in glycogen-glucose was found to be 83-92% of the ratio in liver free glucose. The H-P differences of glucose, lactate, pyruvate, and alanine during feeding were determined. It was found that the H-P difference of (glc) was about 9 times greater than the combined total of ..delta.. (lac), ..delta.. (pyr), and ..delta.. (ala) as early as 10 minutes after the onset of feeding. It is concluded that the direct pathway for the replenishment of hepatic glycogen is predominant and can account for more than 80% of the total glycogen synthesized in vivo in the postprandial state, in contrast to the result of < 30% reported previously by Newgard et al in acute traumatized rats.
- Research Organization:
- NIAAA, Rockville, MD
- OSTI ID:
- 5995841
- Report Number(s):
- CONF-870644-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 46:6; ISSN FEPRA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ALANINES
ALDEHYDES
AMINO ACIDS
ANIMALS
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL MATERIALS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
BLOOD
BLOOD PLASMA
BODY
BODY FLUIDS
CARBOHYDRATES
CARBON 14 COMPOUNDS
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
DIGESTIVE SYSTEM
FASTING
GLANDS
GLUCOSE
GLYCOGEN
HEXOSES
INGESTION
INTAKE
ISOTOPE APPLICATIONS
KETO ACIDS
KINETICS
LABELLED COMPOUNDS
LACTATES
LIVER
MAMMALS
MATERIALS
MONOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
POLYSACCHARIDES
PYRUVIC ACID
RATS
REACTION KINETICS
RODENTS
SACCHARIDES
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VERTEBRATES