USE OF SUPERFUSED RAT SKELETAL-MUSCLE FOR METABOLIC STUDIES - ASSESSMENT OF PH BY P-31 NMR

We developed a muscle superfusion system suitable for metabolic studie s of small isolated rat muscle ex vivo in real time and in a non-destr uctive manner by n.m.r. spectroscopy. In order to determine biochemica l stability of superfused extensor digitorum longus (EDL) muscle (from fasted 45 and 100 g rats), the energy state and the pH of muscle were continuously monitored by P-31 n.m.r. spectroscopy. ATP and phosphocr eatine remained stable during 2 h whatever the muscle size (20 or 45 m g). Neither metabolite was a sensitive probe of possible metabolic com partmentation within muscle under our experimental conditions. By cont rast, the chemical shift of P(i) by its sensitivity to pH was a discri minant factor in the assessment of muscle stability. Indeed, heterogen eity of pH was observed only in the 45 mg EDL muscle resulting from a core region with loss of glycogen. Together, these observations sugges t deviations of energy metabolism to supply ATP. Consequently, pH may be considered as a new real-time criterion for monitoring a metabolic heterogeneity due to changes in energy metabolism of muscle preparatio ns ex vivo.