Enhanced hepatic gluconeogenic capacity for selected precursors following endurance training. Sumida, Ken D., Casey M. Donovan. Department of Exercise Science, University of Southern California, Los Angeles, CA 90089-0652
APStracts 2:0307A, 1995.
The effects of endurance training (running 90 min/day, 30 m/min @ 10% grade) on hepatic gluconeogenesis were studied in 24-h-fasted rats using the isolated liver perfusion technique. Following isolation, livers were perfused (single-pass) for 30 min with Krebs-Henseleit bicarbonate buffer and fresh bovine erythrocytes (hematocrit 22-24%) with no added substrate. Alanine (10 mM), dihydroxyacetone (20 mM) or glutamine (10 mM) were then added to the reservoir and perfusions continued for 60 minutes. No significant differences were observed in perfusate pH, hematocrit, bile production, or serum alanine aminotransferase effluxing from trained or control livers for any perfusion. Trained livers perfused with 10 mM alanine demonstrated significantly higher rates of glucose production, 0.51 + 0.04 mmole/min x g liver-1, compared to controls, 0.40 + 0.02 mmole/min x g liver-1. Elevations of a similar magnitude were observed for rates of 14C-alanine incorporation into 14C-glucose from trained, 8797 + 728 dpm/min x g liver-1, versus control livers, 6962 + 649 dpm/min x g liver-1. Significant increases were also observed in hepatic alanine uptake (30%), oxygen consumption (23%), urea release (22%), and 14CO2 production (27%) from endurance trained livers. In contrast, no significant differences between groups were observed for hepatic glucose output (HGO) following perfusions with either dihydroxyacetone (DHA), 1.75 + 0.06 mmole/min x g liver-1, or glutamine (GLN), 0.62 + 0.04 mmole/min x g liver-1. Further, during perfusions with dihydroxyacetone and glutamine, training had no significant impact upon precursor uptake, oxygen consumption, nor urea output. The current findings indicate a training-induced adaptation for hepatic gluconeogenesis located below the level of the triose phosphates. 

Received 17 January 1995; accepted in final form 6 July 1995.
APS Manuscript Number A54-5.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 18 July 1995.