Oxygen tension gradients and heterogeneity in the venous
microcirculation: a phosphorescence quenching study.
Shonat, Ross D., and Paul C. Johnson.
Department of Physiology, University of Arizona, Tucson, Arizona
85724
APStracts 3:0486H, 1996.
Localized measurements of intravascular oxygen tension (PO2) at
multiple locations in the microvascular network of the rat
spinotrapezius muscle were used to study the spatial distribution of
PO2 in venular structures. Using 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 mmHg ( SD) 33 ( 9, 21 ( 9, 26 ( 10, and 33
( 8 in small arcade arterioles (AA), postcapillary venules (PV), 3o
venules (3V), and arcade venules (AV), respectively. The coefficient
of variation (CV), a descriptive indicator of spatial heterogeneity,
was correspondingly 0.28, 0.45, 0.37, and 0.23 for the different
vessel groups. PO2 was found to increase significantly (P <
0.001) from postcapillary venule to 3o venule, rising 0.009 ( 0.002
mmHg per (m along the vessel. By linear regression, the slope of PO2
for the vessel difference group, PV-3V, as a function of mean
systemic blood pressure (BPm, in mmHg) was -0.09 ( 0.04 (p <
0.05), indicating that the measured longitudinal oxygen gradients and
CV are only weakly dependent on BPm. The results support the
hypothesis that oxygen can diffuse across the walls of postcapillary
vessels and suggests that the postcapillary venular structures are
not merely passive conduits for removing oxygen and waste products,
but may play an important role in regulating oxygen delivery.
Received 20 May 1996; accepted in final form 30 October 1996.
APS Manuscript Number H462-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 31 December 1996