In vivo portal-hepatic venous gradients of glycogenic precursors and incorporation of D-(3- sup 3 H)glucose into liver glycogen in the awake rat
- National Institute on Alcohol Abuse and Alcoholism, Rockville, MD (USA)
Male Wistar fed rats were chronically cannulated and fed ground chow for 2 h for 6 days. On the 7th post-operative day, blood was simultaneously drawn from the portal and hepatic veins over a 2-h feeding period. The position of the hepatic vein cannula was verified using a tritiated water washout technique. In separate experiments, 200 microCi of (3-3H)glucose was added to the food in order to determine the contribution of D-glucose and 3-C precursors to newly synthesized glycogen. The 22-h fasting plasma portal vein concentrations of D-glucose, L-lactate, and L-alanine were 4.8 +/- 0.03, 0.81 +/- 0.06, and 0.20 +/- 0.03 mM, respectively (n = 5). The fasting hepatic vein plasma concentrations were 5.1 +/- 0.2, 0.70 +/- 0.15 and 0.19 +/- 0.03 mM, respectively. The portal-hepatic vein gradients after 22 h were -0.24, +0.16, and +0.01 mM for D-glucose, L-lactate, and L-alanine, respectively. At 20 min after beginning the meal, the respective gradients were +2.2, +0.53, and +0.44 mM, indicating hepatic uptake of all glycogen precursors. Of the total carbon from the three major precursors entering the liver as C-6, D-glucose contributed 82%, while alanine and lactate contributed 18% at 20 min. As portal vein D-glucose and L-alanine levels exceeded 6.65 +/- 0.69 and 0.32 +/- 0.07 mM, respectively, the portal-hepatic venous gradient became positive and increased linearly with portal concentrations. The glycogen concentration in the liver increased from a 22-h fast value of 5 mumol of glucosyl units/g wet weight to 101 +/- 7 mumol/g 2 h after the meal. The mean specific activity of portal vein plasma of (3-3H)glucose was 11,490 +/- 1,180 dpm/mumol (+/- S.E.) and that in the glycogen isolated from liver was 8,175 +/- 785 dpm/mumol of glycosyl units 2 h after the meal. The specific activity of liver (3H)glycogen relative to glucose after the meal was 0.73 +/- 0.08.
- OSTI ID:
- 6511722
- Journal Information:
- Journal of Biological Chemistry; (USA), Journal Name: Journal of Biological Chemistry; (USA) Vol. 265:27; ISSN JBCHA; ISSN 0021-9258
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ALANINES
ALDEHYDES
AMINO ACIDS
ANIMALS
BIOSYNTHESIS
BLOOD VESSELS
BODY
CARBOHYDRATES
CARBOXYLIC ACID SALTS
CARBOXYLIC ACIDS
CARDIOVASCULAR SYSTEM
DIGESTIVE SYSTEM
GLANDS
GLUCOSE
GLYCOGEN
HEXOSES
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
LACTATES
LIVER
MAMMALS
METABOLISM
MONOSACCHARIDES
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANS
POLYSACCHARIDES
PRECURSOR
RATS
RODENTS
SACCHARIDES
SYNTHESIS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
VEINS
VERTEBRATES