Microvascular and interstitial Po2measurements in rat skeletal muscle by phosphorescence quenching

Open Access
Publisher Website
Google Scholar
Abstract
To clarify the transport of O2across the microvessels in skeletal muscle, we designed an intravital laser microscope that utilizes a phosphorescence quenching technique to determine both the microvascular and tissue Po2. After we injected the phosphorescent probe into systemic blood, phosphorescence excited by a N2-dye pulse laser was detected with a photomultiplier over a 10 μm in diameter area. In vitro and in vivo calibrations confirmed that the present method is accurate for Po2measurements in the range of 7–90 Torr ( r= 0.958) and has a rapid response time. This method was then used to measure the Po2of microvessels with different diameters (40–130 μm) and of interstitial spaces in rat cremaster muscle. These measurements showed a significant drop in Po2in the arterioles after branching (from 74.6 to 46.6 Torr) and the presence of a large Po2gradient at the blood-tissue interface of arterioles (15–20 Torr). These findings suggest that capillaries are not the sole source of oxygen supply to surrounding tissue.