HEPATIC GLUCONEOGENESIS FROM LACTATE AFTER ENDURANCE TRAINING IN YOUNG & OLD RATS: EFFECTS OF VARIOUS CONCENTRATIONS OF EPINEPHRINE

Abstract

86 The effects of endurance training on hepatic gluconeogenesis were studied in 24 hr fasted young (4 mo) and old (24 mo) male Fischer 344 rats using the isolated hepatocyte technique. After isolation of the hepatocytes, aliquots of the cell suspension were placed in a 37C water bath with gentle shaking and gassed with O2/CO2 (95%:5%). The hepatocytes were pre-incubated for 10 min with 5 mM lactate prior to the addition of epinephrine (Epi). The [Epi] used were (nM): 0,10,25,50,100,250,500,1000,5000, and 10,000. Basal (no Epi) hepatic glucose production (HGP) from lactate was 29% higher from the cells of young trained (YT) animals compared to the aged matched controls (YC). Endurance training resulted in no significant difference in the Km. At Vmax, there was a 32% and 34% increase in HGP above basal levels in YT and YC, respectively. In addition, the cells from YT maintained the 30% increase in HGP at all [Epi] compared to the cells from YC. In contrast, HGP was not affected by endurance training in the cells from old animals at basal or any [Epi]. The findings suggest that endurance training results in a ∼30% elevation in basal HGP from the hepatocytes of young, but not old animals. Finally, the 30% increase is maintained at all [Epi]. Supported by NIH grant AG 14565