Measurement of Oxygen in the Microcirculation Using Phosphorescence Quenching Microscopy
According to the classical concept of Krogh, O2 is delivered to the tissues solely by capillaries and intra-capillary resistance to O2 diffusion is negligible. Over the past three decades longitudinal PO2 and SO2 gradients in arterioles have been observed with a transmural PO2 gradient in small arterioles of only 1–2 mmHg. Application of phosphorescence quenching microscopy to measurements of PO2 in arterioles of the rat mesentery by Tsai et al. (1998) found a large transmural PO2 in these arterioles. That led to the provocative conclusion that the arteriolar wall is the major sink for O2 in the microcirculation. Our studies indicate that many of these results can be explained by photo-activated O2 consumption following phosphor excitation, combined with a large excitation area and high frequency of flash excitation. We have developed the basic principles for phosphorescence quenching microscopy including the need to use a small excitation area, a low excitation frequency and a scanning excitation for stationary samples.
KeywordsExcitation Region Hamster Cheek Pouch Arteriolar Wall Flash Frequency Multiple Excitation
Supported by grant AHA-0655449U from the American Heart Association, Mid-Atlantic Affiliate and grants HL18292 and HL079087 from the NHLBI.
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