In situ monitoring of PO2 and VO2 in skeletal muscle microcirculation

We employed phosphorescence quenching microscopy to monitor interstitial PO 2 in 0.3 mm i.d. regions of the spinotrapezius muscles of 5 anesthetized rats (25 regions). The oxygen probe was loaded into the interstitial space and PO 2 was sampled once per second. Every 20 s the muscle was pneumatically compressed for 5s to remove blood and to record the rate of oxygen disappearance ( dP/dt) caused by combined O 2 consumption by the tissue and method. Auto‐consumption was measured by comparison of dP/dt at 1 and 10 Hz flash rates. Muscle VO 2 was calculated after correcting dP/dt for autoconsumption. PO 2 at normal perfusion ( Po , mmHg), and VO 2 (mlO 2 /min·100cm 3 ) were recorded in resting muscle (1 min), during electrical stimulation (2 min, 10V, 2 Hz, 20 ms) and recovery (2 min). In resting muscle Po was 72±1 (75) [ M±SE (n) ] and VO 2 was 0.99±0.03 (75). Contraction caused Po to drop to 38±1 (150) and VO 2 to increase to 3.22 ± 0.10 (150) within 20 s. Post‐contraction recovery of PO 2 and VO 2 was exponential (time constant 50 s) and was not complete within 2 min. Following the end of stimulation, VO 2 remained high for 20 s and returned to resting levels with a 20 s delay with respect to the PO 2 time course. Support: NIH‐HL18292