AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 5 1447-R1451, Copyright © 1996 by American Physiological Society
Regulation of skeletal muscle metabolism in the lizard Dipsosaurus dorsalis by fructose-2,6-bisphosphate
D. A. Scholnick and T. T. Gleeson
University of Colorado, Department of Environmental Population and Organismic Biology, Boulder 80309-0334, USA. Scholnic@samiam.colorado.edu
Changes in liver and skeletal muscle fructose-2,6-bisphosphate (Fru-2,6-P2)
concentrations were compared during fasting, exercise, and recovery in the
lizard Dipsosaurus dorsalis and in outbred mice (Mus musculus). We present
the first correlative evidence that suggests that a decrease in the content
of Fru-2,6-P2 may mediate elevated gluconeogenesis in lizard skeletal
muscle. Contents of Fru-2,6-P2 in lizard gastrocnemius and red and white
iliofibularis (IF) were significantly lower (as much as 55% in white IF)
during recovery from exhaustive exercise than at rest. Recovery from
exhaustive exercise had no significant effect on Fru-2,6-P2 concentrations
in any mouse muscle examined. Fasting significantly depressed lizard and
mouse liver Fru-2,6-P2 contents and decreased lizard red IF by over 84%
from the fed condition. Lizard red and white muscle fiber bundles incubated
in 20 mM lactate had significantly lower Fru-2,6-P2 (94 and 61% depression,
respectively) than those incubated in 8.5 mM glucose. These results are
consistent with the hypothesis that Fru-2,6-P2 acts as a signal for
controlling gluconeogenesis in lizard skeletal muscle.
