Voluntary activity, cardiovascular and muscular responses to anemia in rats
Edgerton, V.R.; Diamond, L.B.; Olson, J.
Journal of Nutrition 107(9): 1595-1601
1977
ISSN/ISBN: 0022-3166 PMID: 894356 Document Number: 124143
Twenty adult rats were divided equally into a control (C) group that had about 7 ml of blood removed retroorbitally and immediately replaced i.p., 6 times over a period of 15 wk, and an anemic (A) group that was bled similarly but reinjected with serum plus physiological saline to replace the blood volume removed. Voluntary activity was significantly less in the A than C group when the Hb dropped to less than about 11 g/100 ml. Seventeen weeks after the initial bleeding, a controlled treadmill test was given. Heart rates were significantly higher in A (410 beats/minute) than C group (370 beats/min) after a 3 min period of exercise. After an exhaustice run, blood lactate was higher in A than C rats. Mean running time for C rats was 23.3 .+-. 2.5 and 11.0 .+-. 1.5 min for the A group. Twitch tension (7 Hz) of the gastrocnemius (in situ) was 50% and 30% of resting tension after 5 min of stimulation in C and A groups, respectively. No difference in the rate of fall of tension was observed when the muscle was tetanized (150 Hz). Exercise apparently places a significantly greater cardiovascular and metabolic stress on anemic than control rats. The significance of this stress is suggested by the low maximal work capacity on the treadmill as well as in the relative fatiguability of the in situ stimulated muscles. Because voluntary activity changes within a few days of when Hb was elevated or lowered beyond a critical point of approximately 110 g Hb/100 ml, these data suggest that Hb is more critical than Fe stores in causing the depressed voluntary activity.