OXYGEN-TENSION GRADIENTS AND HETEROGENEITY IN VENOUS MICROCIRCULATION- A PHOSPHORESCENCE QUENCHING STUDY

Localized measurements of intravascular oxygen tension (PO2) at multip le locations in the microvascular network of the rat spinotrapezius mu scle were used to study the spatial distribution of PO2 in venular str uctures. By use of a newly developed phosphorescence system to rapidly and repeatedly measure PO2, 538 individual measurements were made in 18 different networks during rest. Average intravascular PO2 was (in m mHg +/- SD) 33 +/- 9, 21 +/- 9, 26 +/- 10, and 33 +/- 8 in small arcad e arterioles, postcapillary venules (PV), 3 degrees venules (3V), and arcade venules, respectively. The coefficient of variation (CV), a des criptive indicator of spatial heterogeneity, was correspondingly 0.28, 0.45, 0.37, and 0.23 for the different vessel groups. PO2 was found t o increase significantly (P < 0.001) from PV to 3V, rising 0.009 +/- 0 .002 mmHg/mu m along the vessel. By linear regression, the slope of PO 2 for the vessel difference group, PV-SV, as a function of mean system ic blood pressure (BPm; in mmHg) was -0.09 +/- 0.04 (P < 0.05), indica ting that the measured longitudinal oxygen gradients and CV are only w eakly dependent on BPm. The results support the hypothesis that oxygen can diffuse across the walls of postcapillary vessels and suggest tha t the venular structures are not merely passive conduits for removing oxygen and waste products but may play an important role in regulating oxygen delivery.