ENERGY-METABOLISM AND INTERSTITIAL FLUID DISPLACEMENT IN HUMAN GASTROCNEMIUS DURING SHORT ISCHEMIC CYCLES

Energy metabolism and interstitial fluid displacement were studied in the human gastrocnemius during three subsequent 5-min ischemia-reperfu sion periods [ischemic preconditioning (IP)]. The muscle energy balanc e was assessed by combining near-infrared spectroscopy (NIRS) and P-31 -nuclear magnetic resonance spectroscopy (P-31-NMRS). The interstitial fluid displacement was determined by combining NIRS and Na-23-NMRS. N o changes in total energy consumption or in the fractional contributio n of the underlying energy sources (aerobic glycolysis, anaerobic glyc olysis, and Lohmann reaction) were observed in the muscle during the t ested IP protocol. Oxygen consumption in the muscle region of interest , as estimated by NIRS, was similar to 8 mu mol . 100 g(-1) min(-1) an d did not change during IF. Phosphocreatine and ATP concentrations did not change over the whole experimental period. A slight but significa nt (P < 0.05) increase in intracellular pH was observed. Compared with the control, a 10% greater interstitial fluid content per muscle unit volume was observed at the end of the IP protocol. It is concluded th at, at variance with cardiac muscle, repeated 5-min ischemia-reperfusi on cycles do not induce metabolic changes in human gastrocnemius but a lter the interstitial fluid readjustment. The techniques developed in the present study may be useful in identifying protocols suitable for skeletal muscle preconditioning and to explain the functional basis of this procedure.