Lactate in rat skeletal muscle after hemorrhage measured by microdialysis probe calibrated in situ

The interstitial lactate concentration in rat skeletal muscle was measured in the normal state and after hemorrhage using a microdialysis probe, and the values calculated by in vitro and in vivo calibration were compared. After withdrawal of 30% of the estimated total blood volume, the lactate concentration in the dialysate gradually increased and then maintained an almost constant level. It was found that interstitial lactate levels of skeletal muscle calculated by the in vitro calibration method were not significantly different from those calculated by in vivo calibration in both the normal state and after hemorrhage. These data indicate that the absolute lactate concentration in the muscle interstitium in the normal state and after acute hemorrhage can be practically measured by a microdialysis probe calibrated in vitro. From the comparison of lactate concentrations in blood and in the muscle interstitium, it was suggested that rat skeletal muscle functions as a lactate consumer, rather than as a lactate producer, after acute hemorrhage.