| Autor: |
Shalwitz, R A, Reo, N V, Becker, N N, Hill, A C, Ewy, C S, Ackerman, J J H |
| Zdroj: |
Journal of Biological Chemistry; March 1989, Vol. 264 Issue: 7 p3930-3934, 5p |
| Abstrakt: |
An in situ and in vivosurface coil 13C NMR study was performed to study hepatic glycogen synthesis from [3-13C]alanine and [1-13C]glucose administered by intraduodenal infusion in 18-h fasted male Sprague-Dawley rats. Combined, equimolar amounts of alanine and glucose were given. Hepatic appearance and disappearance of substrate and concurrent glycogen synthesis was followed over 150 min, with 5-min time resolution. Active glycogen synthesis from glucose via the direct (glucose→glycogen) and indirect (glucose→lactate→glycogen) pathways and from alanine via gluconeogenesis was observed. The indirect pathway of glycogen synthesis from [1-13C]glucose accounted for 30% (±6 S.E.) of total glycogen formed from labeled glucose. This estimate does not take into account dilution of label in the hepatic oxaloacetate pool and is, therefore, somewhat uncertain. Hepatic levels of [3-13C]alanine achieved were significantly lower than levels of [1-13C]glucose in the liver, and the period of active glycogen synthesis from [3-13C]alanine was longer than from glucose. However, the overall pseudo-first-order rate constant during the period of active glycogen synthesis from [3-13C]alanine (0.075 min−1± 0.026 S.E.) was almost 3 times that from [1-13C]glucose via the direct pathway (0.025 min−1± 0.005 S.E.). The most likely reason for the small rate constant governing direct glycogen formation from duodenally administered glucose compared to that from duodenally administered alanine is a low level of glucose phosphorylating capacity in the liver. |
| Databáze: |
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