Effect of Endurance Training and Fasting on Renal Gluconeogenic Enzymes in the Rat

Abstract

The purpose of this study was to examine the effects of chronic exercise training (running 30 m/min, 10% grade, 90 min/d for 8–10 weeks) on specific renal enzyme activities involved with the gluconeogenic pathway in the fed and 24-hr fasted state in rats. A portion of the kidney (containing the cortex and medulla) was homogenized from which cytosolic (c) and mitochondrial (m) fractions were separated. Maximal gluconeogenic enzyme activities were assessed for: phosphoenolpyruvate carboxykinase (cPEPCK), fructose 1,6-bisphosphatase (cFBP), pyruvate carboxylase (mPC), aspartate aminotrans-ferase (cAspAT), alanine aminotransferase (cAlaAT), and lactate dehydroge-nase (cLDH). In the fed state, there was no significant difference between groups in any of the enzymes examined (nmoles/min × mg protei n–1): cPEPCK (25.8 ± 1.7), cFBP(106.8 ± 7.1), mPC (20.7 ± 1.8), cAspAT( 1047.1 ±38.6), cAlaAT (52.3 ±4.3), and cLDH(1728.6± 163.2). After the 24-hr fast, there was a significant increase in cPEPCK (52.4 ± 2.9 and 52.0 ± 2.1) and mPC (44.6 ± 4.3 and 47.6 ± 4.9), control and trained, respectively. These results suggest that the maximal enzyme activities for cPEPCK and mPC can be augmented as a result of fasting that was independent of the training status.