Determination of po2 and its heterogeneity in single
capillaries.
Zheng, Lei, Aleksander S. Golub, and Roland N. Pittman.
DEPARTMENT OF PHYSIOLOGY, MEDICAL COLLEGE OF VIRGINIA, VIRGINIA
COMMONWEALTH UNIVERSITY, RICHMOND, VA 23298-0551
APStracts 2:0537H, 1995.
We have applied the phosphorescence lifetime technique (J. Biol. Chem.
262:5476, 1987) to determine oxygen tension in single capillaries of
the hamster retractor muscle. Palladium meso-tetra (4-carboxyphenyl)
porphine (10 mg/ml, pH 7.40, bound to bovine serum albumin) was used
as the phosphorescent oxygen sensor. Our measurement system consisted
of a microscope configured for epi-illumination, a strobe flash lamp,
a 430 nm bandpass excitation filter and a 630 nm cut-on emission
filter. A rectangular diaphragm was used to limit the illumination
field to 10 [mu]m _ 10 [mu]m, and an end window photomultiplier tube
was used to detect the phosphorescence signal, that was then input to
an analog-to-digital board in a personal computer. In vitro
calibrations were carried out at 37 oC on samples flowing through a
glass capillary tube (diameter = 300 [mu]m) at four different O2
concentrations (in %): 0, 2.5, 5 and 7.5. In vivo tests were carried
out on arterioles, capillaries and venules of the retractor muscle of
anesthetized hamsters. The phosphorescent compound was administered
by injection into a jugular vein (20 mg/kg). Phosphorescence decay
curves were analyzed by a new model of heterogeneous oxygen
distribution in the excitation/emission volume. Mean PO2 and the
local PO2 gradient within the excitation/emission volume were
calculated from phosphorescence lifetimes obtained from individual
decay curves. The time course of PO2 obtained during 0.5 s
measurement periods (5 decay curves at 0.1 s intervals) at a given
site along a capillary indicated the presence of a gradient in PO2
within the plasma space between and near red blood cells. Similar PO2
gradients were also detected in arterioles and venules. The mean (+/-
SD) PO2 for arterioles, capillaries and venules over the 0.5-s
observation period was 27+/-5, 14+/-2 and 11+/-3 mm Hg, respectively.
The magnitude of the PO2 gradient in the arterioles, capillaries and
venules was 6+/-1, 4+/-1 and 2+/-1 mm Hg/[mu]m, respectively.
Received 19 July 1995; accepted in final form 22 November 1995.
APS Manuscript Number H679-5.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95