Visualization of the oxygen level inside a single cardiac myocyte
.
Takahashi, Eiji, and Katsuhiko Doi.
Department of Physiology, Yamagata University School of Medicine,
Yamagata 990-23, Japan
APStracts 2:0019H, 1995.
The present paper describes theoretical and experimental bases for
quantitation of the oxygen level inside an individual single
ventricular myocyte isolated from the rat. We applied a 3-wavelength
microspectrophotometry to a single cardiomyocyte, where the
sensitivity of the spectrophotometry was augmented by digital image
processing technique known as the video-enhanced microscopy (VEM).
Oxygen dependent changes in light absorption of the intracellular
pigments were detected and represented using a newly defined
variable, Z, where one pixel of the reconstructed cell image
corresponded to 0.2 m. Theoretically, Z is a single-valued function
of the fractional oxygen saturation of the intracellular pigment. We
demonstrated in quiescent cardiomyocytes that Z changed according to
extracellular Po2 where the relationship was sigmoidal with the
extracellular Po2 for half maximal Z of 3.2 Torr. In the aerobic
cell, conversion of cytochromes to the reduced forms by NaCN did not
affect Z value. Therefore, we conclude that Z mainly represents the
fractional oxygen saturation of myoglobin thus reporting cytosolic
Po2. We also demonstrated that for extracellular Po2 of 1.3 Torr
abolition of mitochondrial oxygen consumption by NaCN significantly
elevated the intracellular oxygen level, suggesting existence of
oxygen pressure gradients in a quiescent single cardiomyocyte that
were proportional to oxygen flux.
Received 14 November 1994; accepted in final form 19 January
1995.
APS Manuscript Number H1010-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 24 February 1995.