In Vivo Microvascular Oxygen Measurements by Phosphorescence Quenching Technique

To clarify the oxygen transport across the microvessels and oxygen distribution in the skeletal muscle, we have newly designed an intravital laser microscopy with oxygen-dependent quenching of phosphorescence technique to determine both the microvascular and the tissue pO
₂
. After injecting the phosphorescent probe into systemic blood, phosphorescence excited by a N
₂
/dye pulse laser was detected with a photomultiplier over a 10 mum in diameter area. In vivo oxygen tension (pO
₂
) measurements revealed the efficiency of this method. This method was then used to measure the pO
₂
of microvessels with different diameters (40-30 mum) and of interstitial spaces in rat cremaster muscle. These measurements showed a significant reduction of pO
₂
levels in arterioles of different orders and the presence of large pO
₂
gradients at the blood/tissue interface of arterioles. These findings suggest that oxygen can be released from larger arterioles and O
₂
consumption of rat cremaster muscle might be high