PH IS REGULATED DIFFERENTLY BY GLUCOSE IN SKELETAL-MUSCLE FROM FED AND STARVED RATS - A STUDY USING P-31-NMR SPECTROSCOPY

The aim of this study was to determine whether exogenous glucose metab olism influences the pH in superfused EDL muscle from growing rats fed or starved for 48 h (body weight 55 and 45 g, respectively). Energy s tate and intracellular pH of muscle were repeatedly monitored by P-31- nuclear magnetic resonance spectroscopy (P-31-NMRS); glycogen and othe r energy metabolites were assayed enzymatically in muscle extracts at the end of the experiment. in EDL muscles from starved rats superfused with glucose for 4 h, intracellular pH was elevated (7-7.3), lactate concentration low, glycogen repletion very intense and citrate synthas e activity high, We conclude that glucose was routed mainly toward bot h oxidative phosphorylation and glycogen synthesis in EDL muscles afte r food deprivation of rats. In contrast, the major pathway in muscles from fed rats may be glycolysis because the glycogen pool remained con stant throughout the experiment, The additional and minor pH component (in the range of 6.5 to 6.8) seen in muscles from fed rats, even in t he presence of exogenous glucose, might De due to impaired glucose uti lization because this component appears also in muscles from starved r ats superfused without glucose or with a nonmetabolizable analog of gl ucose, Consequently, direct pH measurement by P-31- NMR may be conside red to be a precise criterion for evaluation of differences in metabol ic potentialities of muscle studied ex vivo in relation to the nutriti onal stale of rats.