Abstract
Summary
Increasing the plasma osmolarity up to 12% with muscular exercise does not measurably change the volume of the erythrocyte in man. The results of this investigation emphasize that indiscriminate extrapolation of observations from in vitro studies to in vivo conditions may lead to erroneous conclusions. There is no evidence that the human red cell in vivo does not behave as an osmometer; however, its reactivity to osmotic changes does not necessarily result in volume changes because of other simultaneously occurring compensatory events. Consequently, the procedure of correcting the measured total relative red cell volume (Hct) for changes in plasma osmolarity should be used with discretion.
The authors thank Dr. J. E. Greenleaf for his advice during the preparation of the manuscript.
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