Flow-dependent influence of high o2 affinity red cells on peak vo2
in exercising muscle in situ.
Kohzuki, H., Y. Enoki, K. Matsumura, S. Sakata, and S. Shimizu.
Department of Physiology, Nara Medical University, Kashihara, Nara
634, Japan
APStracts 2:0452A, 1995.
To evaluate the influence of a high O2 affinity of the erythrocyte and
of flow rate on muscle's ability to extract O2 and develop force, we
perfused dog gastrocnemius contracting isometrically at 4 Hz with
normal O2 affinity perfusate or high O2 affinity perfusate at high
and moderate flows (200 and 100 ml.min-1.100g-1, respectively). High
O2 affinity perfusate was prepared by incubating human CPD-stored red
cells with buffered saline containing cyanate (4 C, 18 hr) and normal
affinity perfusate by storing 2, 3-diphospho glycerate-rejuvenated
red cells in the same solution without cyanate. P50 (oxygen partial
pressure when blood is half oxygenated) was 30.6 Torr for normal
perfusate and 18.1 Torr for high affinity perfusate. During 4-Hz
stimulation, the tension developed by the muscle increased
incrementally (positive staircase) to reach a peak value after 1.2
-1.6 min for the normal perfusate and 0.6-0.7 min for the high
affinity perfusate (P<0.05). The rate of decline during the early
fatigue (measured from the onset of tension decline to 3 min) with
high affinity perfusate was significantly faster than it was with
normal perfusate (P<0.05). These findings suggest that both the
staircase effect and the early fatigue are related to O2
availability, which is restricted when red cells have a high O2
affinity. The peak Vo2 values (Vo2,peak) measured at 3 and 5 min were
significantly lower (by 14-24 %) with high affinity perfusate than
with normal perfusate at a given level of O2 delivery (arterial O2
content X flow) (P<0.05). Pvo2 (Po2 of venous effluent) was
proportionally related to Vo2,peak. The present results indicate that
neither blood flow nor O2 delivery is the sole determinant of the
muscle's ability to extract O2.
Received 18 October 1994; accepted in final form 6 October 1995.
APS Manuscript Number A1069-4.
Article publication pending Journal of Applied Physiology.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 6 November 95