AJP - Endocrinology and Metabolism, Vol 251, Issue 4 385-E392, Copyright © 1986 by American Physiological Society
Effects of alanine on malate-aspartate shuttle in perfused livers from cold-exposed rats
T. Sugano, T. Ohta, A. Tarui and Y. Miyamae
The role of glucocorticoids in the increase by cold-exposure of the effect
of alanine on the malate-aspartate shuttle was studied in perfused rat
liver. The capacity of the shuttle was evaluated by measurement of changes
in both the rate of glucose production from sorbitol and the ratio of
lactate to pyruvate during ethanol oxidation (Biomed. Res. 6, Suppl.,
1986). The effect of alanine on the shuttle capacity was decreased by
adrenalectomy. When 1.5 mg/kg dexamethasone sulfate was administrated to
adrenalectomized rats kept at 24 or 4 degrees C, once daily for 5 days, the
effect of alanine on the shuttle increased its capacity to the level of
sham-operated rats that had been exposed to 4 degrees C for 5 days. The
effects of dexamethasone were blocked by the coadministration of
tetracycline with the agent. Cold exposure and steroid replacement had
little effect on the alanine-induced elevation of the levels of aspartate,
glutamate, and alpha-ketoglutarate in liver cells. The increase of the
effect of alanine could not be explained only by changes in the activity of
NAD+ malate dehydrogenase and aspartate aminotransferase. The results
suggest that cold exposure and replacement treatment with glucocorticoids
modulate equally the effect of alanine on the capacity of the
malate-aspartate shuttle.
