Gluconeogenesis is reduced from alanine, lactate and pyruvate, but maintained from glycerol, in liver perfusion of rats with early and late sepsis

The present study was conducted to examine the effect of a single bout of exercise (rodent treadmill, 60 min at 26 m/min, 0% grade) on the gluconeogenic activity of periportal hepatocytes (PP-H) and perivenous hepatocytes (PV-H) in fasted (18 h) rats. Isolated PP-H and PV-H, obtained by selective destruction following liver perfusion with digitonin and collagenase, were incubated with saturating concentrations of alanine (Ala; 20 mM) or a mixture of lactate and pyruvate (Lac+Pyr; 20:2 mM) to determine the glucose production flux ( J glucose) in the incubation medium. Results show that, in the resting conditions, J glucose from all exogenous substrates was significantly higher ( P < 0.01) in PP-H than in PV-H. Exercise, compared with rest, resulted in a higher J glucose ( P < 0.01) from Lac+Pyr substrate in the PV-H but not in the PP-H, resulting in the disappearance of the difference in J glucosebetween PP-H and PV-H. Exercise, compared with rest, led to a higher J glucose ( P < 0.01) from Ala substrate in both PP-H and PV-H. However, the exercise-induced increase in J glucose (gluconeogenic activity) from Ala substrate was higher in PV-H than in PP-H, resulting, as from Lac+Pyr substrate, in the disappearance ( P > 0.05) of the difference of J glucose between PP-H and PV-H. It is concluded that exercise differentially stimulates the gluconeogenic activity of PV-H to a larger extent than PP-H, indicative of a heterogenous metabolic response of hepatocytes to exercise.

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Carbon-14 Tracer Studies in Rat-Liver Perfusion Experiments under Conditions of Gluconeogenesis from Lactate and Pyruvate

European Journal of Biochemistry ◽

10.1111/j.1432-1033.1977.tb11532.x ◽

1977 ◽

Vol 75 (2) ◽

pp. 319-330 ◽

Cited By ~ 17

Author(s):

Gerd MULLHOFER ◽

Andreas SCHWAB ◽

Claudia MULLER ◽

Christel STETTEN ◽

Edwige GRUBER

Keyword(s):

Rat Liver ◽

Liver Perfusion ◽

Tracer Studies ◽

Rat Liver Perfusion ◽

Carbon 14 ◽

Lactate And Pyruvate

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Regulation of glycogen synthesis from glucose and gluconeogenic precursors by insulin in periportal and perivenous rat hepatocytes

Biochemical Journal ◽

10.1042/bj2660091 ◽

1990 ◽

Vol 266 (1) ◽

pp. 91-102 ◽

Cited By ~ 45

Author(s):

L Agius ◽

M Peak ◽

K G M M Alberti

Keyword(s):

Initial Rate ◽

Liver Perfusion ◽

Glycogen Synthesis ◽

Rat Hepatocytes ◽

Nutritional State ◽

Glycogen Accumulation ◽

Hepatocyte Cultures ◽

Lactate And Pyruvate ◽

High Concentrations ◽

Glycogen Deposition

Glycogen synthesis in hepatocyte cultures is dependent on: (1) the nutritional state of the donor rat, (2) the acinar origin of the hepatocytes, (3) the concentrations of glucose and gluconeogenic precursors, and (4) insulin. High concentrations of glucose (15-25 mM) and gluconeogenic precursors (10 mM-lactate and 1 mM-pyruvate) had a synergistic effect on glycogen deposition in both periportal and perivenous hepatocytes. When hepatocytes were challenged with glucose, lactate and pyruvate in the absence of insulin, glycogen was deposited at a linear rate for 2 h and then reached a plateau. However, in the presence of insulin, the initial rate of glycogen deposition was increased (20-40%) and glycogen deposition continued for more than 4 h. Consequently, insulin had a more marked effect on the glycogen accumulated in the cell after 4 h (100-200% increase) than on the initial rate of glycogen deposition. Glycogen accumulation in hepatocyte cultures prepared from rats that were fasted for 24 h and then re-fed for 3 h before liver perfusion was 2-fold higher than in hepatocytes from rats fed ad libitum and 4-fold higher than in hepatocytes from fasted rats. The incorporation of [14C]lactate into glycogen was 2-4-fold higher in periportal than in perivenous hepatocytes in both the absence and the presence of insulin, whereas the incorporation of [14C]glucose into glycogen was similar in periportal and perivenous hepatocytes in the absence of insulin, but higher in perivenous hepatocytes in the presence of insulin. Rates of glycogen deposition in the combined presence of glucose and gluconeogenic precursors were similar in periportal and perivenous hepatocytes, whereas in the presence of glucose alone, rates of glycogen deposition paralleled the incorporation of [14C]glucose into glycogen and were higher in perivenous hepatocytes in the presence of insulin. It is concluded that periportal and perivenous hepatocytes utilize different substrates for glycogen synthesis, but differences between the two cell populations in the relative utilization of glucose and gluconeogenic precursors are dependent on the presence of insulin and on the nutritional state of the rat.

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