Interstitial PO₂Determination by Phosphorescence Quenching Microscopy

Abstract

Objective:This study introduces the technique of microinjection of phosphor probe into skeletal muscle tissue to determine oxygen tension (PO₂) in the interstitium by phosphorescence quenching microscopy. Method:The spinotrapezius muscle of Wistar-Kyoto rats weighing 240–280 g was surgically isolated and underwent the microinjection procedure. We measured the spatial distribution of phosphor probe 10, 30, and 80 minutes after injection; the tissue PO₂at sites adjacent to arteriolar and venular microvessels; and the decline in tissue PO₂during a 3-minute period of 8-Hz contraction. Results:The phosphorescence signal from the probe was undetectable outside a 2.5-mm radius from the site of injection at the 10-minute time point, increased to measurable values after 30 minutes, and was double the 30-minute intensity value after 80 minutes. When used to measure periarteriolar PO₂, the tissue microinjection technique demonstrated a nonlinear fall in tissue PO₂with distance away from secondary arterioles (30–40 µm diameter). Conversely, perivenular tissue PO₂increased in a nonlinear manner with distance away from secondary venules (60–70 µm diameter). The tissue PO₂at distances of 16 µm and greater from both types of secondary microvessels was significantly different from values taken directly over the centerline of these microvessels. During muscle contraction, the PO₂fell from a mean precontraction value of 28.3 ± 4.9 mmHg to 8.2 ± 0.9 mmHg at the end of the contraction period. Conclusions:These observations indicate that the microinjection technique yields values for tissue PO₂that are in good agreement with previously published results using oxygen microelectrodes. Microcirculation(2002) 9,389–395. doi:10.1038/sj.mn.7800147

• muscle contraction
• rat
• spinotrapezius muscle