AJP - Heart and Circulatory Physiology, Vol 253, Issue 2 454-H460, Copyright © 1987 by American Physiological Society
Effect of MCA occlusion on brain O2 supply and consumption determined microspectrophotometrically
E. Buchweitz-Milton and H. R. Weiss
This study compared oxygen extraction, oxygen consumption, and cerebral
blood flow (CBF) in the ischemic and contralateral cortex of middle
cerebral artery (MCA)-occluded feline brain using a microspectrophotometric
technique. This technique was further validated in several experiments. A
transorbital approach exposed the right MCA. After preocclusion blood
pressure, heart rate, and blood gas values were determined, radioactively
labeled microspheres (15 +/- 3 microns diam) were injected intra-atrially.
The right MCA was then occluded. These same measurements were taken 1 h
later. Arterial and venous oxygen saturations were determined in the center
and surrounding area of the occluded ischemic cortex and other brain
regions. Regional cerebral oxygen consumption was determined as the product
of CBF and oxygen extraction. CBF decreased significantly from 54.0 +/- 5.0
to 26.6 +/- 4.8 (mean +/- SE) ml X min-1 X 100 g-1 in the center of the
ischemic cortex and from 49.6 +/- 7.0 to 30.6 +/- 5.0 ml X min-1 X 100 g-1
in the surrounding ischemic cortex. Oxygen extraction was significantly
increased from 3.7 +/- 0.4 ml O2/100 ml blood to 4.6 +/- 0.6 ml O2/100 ml
blood in the center of the occluded cortex but was not significantly
altered in the surrounding moderately ischemic cortex. Oxygen consumption
was not significantly altered in either ischemic cortical region when
compared with the contralateral cortices. Unilateral MCA occlusion caused a
decreased regional CBF associated with increased brain oxygen extraction in
the cortical region directly supplied by the MCA. The feline brain appears
to maintain oxygen consumption in the occluded cortex by increasing oxygen
extraction.
