Journal of Applied Physiology, Vol 50, Issue 3 597-604, Copyright © 1981 by American Physiological Society
Blood volume and plasma protein responses to heat acclimatization in humans
M. H. Harrison, R. J. Edwards, M. J. Graveney, L. A. Cochrane and J. A. Davies
The effects of heat acclimatization on intravascular volume and protein
responses to acute heat stress and exercise were studied in six male
subjects. Absolute values for hematocrit and hemoglobin concentration were
lower after, than before, acclimatization, indicating hemodilution. Also,
after acclimatization, the magnitude of the hemoconcentration response to
exercise in the heat was significantly increased. There ws no change in the
concentration of plasma protein during or after acclimatization compared
with before acclimatization, but there was a net increase in the total
intravascular protein content. It is suggested that the hemodilution
associated with heat acclimatization may be explained in terms of an
increase in the intravascular oncotic pressure following an
exercise-induced augmentation of protein, occurring at the expense of the
interstitial compartment. It is concluded that this hemodilution is
unlikely to be primarily responsible for the cardiovascular adjustment
accompanying heat acclimatization and that it should be regarded as a
secondary feature of adaptation to heat.
