Time-dependent changes in the contribution of gluconeogenic precursors and glucose to glycogenesis in isolated rate hepatocytes
Hepatocytes from 21-hr fasted rats were incubated for up to 60 min with 10 mM glucose and gluconeogeneic precursors: 4 mM lactate/0.4 mM pyruvate plus 5 mM alanine and 2 mM fructose or 10 mM glutamine. Tracer 3-/sup 3/H,U-/sup 14/C-glucose was added 15 min before terminating the incubations. In all cases, the /sup 3/H and /sup 14/C specific activities of the newly synthesized glycogen increased over time, relative to the specific activities of medium glucose. The percentage of new carbon in glycogen originating from glucose increased from less than 50% in the first 15 min to over 85% after 30 min. Relative to medium glucose, the ratio of /sup 3/H:/sup 14/C in glycogen was about 0.9 through-out the incubations, indicating direct incorporation of glucose into glycogen without significant prior transformation via the pentose pathway or recycling to triose phosphates. Insulin did not stimulate glucose incorporation into glycogen. 3-Mercaptopicolinate decreased the incorporation of precursor carbon into glycogen during incubations with glutamine but not during incubations with fructose and alanine. These data indicate time-dependent and reciprocal changes in rates of glucose-6-P synthesis from gluconeogenic precursors and glucose. Activation of glucokinase may underlie the increased contribution of glucose to glycogenesis. Thus, the relative importance of glucose and gluconeogenic precursors as substrates for glycogenesis directly reflects their respective contributions to the cellular pool of the glucose-6-P.
- Research Organization:
- Cornell Univ., Ithaca, NY
- OSTI ID:
- 6991286
- Report Number(s):
- CONF-8606151-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
- Country of Publication:
- United States
- Language:
- English
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59 BASIC BIOLOGICAL SCIENCES
ALDEHYDES
ANIMAL CELLS
BIOLOGICAL PATHWAYS
BIOSYNTHESIS
CARBOHYDRATES
CARBON 14 COMPOUNDS
GLUCOSE
GLYCOGEN
HEXOSES
ISOTOPE APPLICATIONS
ISOTOPE RATIO
LABELLED COMPOUNDS
LIVER CELLS
METABOLISM
MONOSACCHARIDES
ORGANIC COMPOUNDS
POLYSACCHARIDES
PRECURSOR
SACCHARIDES
SOMATIC CELLS
SYNTHESIS
TIME DEPENDENCE
TRACER TECHNIQUES
TRITIUM COMPOUNDS