SEASONAL FLUCTUATIONS IN BLOOD VOLUME

Abstract

The plasma volume was measured by T1824 dilution in groups of normal young male subjects at regular intervals over the course of 3 years. The plasma volume increased during the summer and decreased during the winter, but this change was variable from subject to subject and was not as marked during 1 year as during the other 2. Ascorbic acid in daily supplement of 400 mg., taken during the first year of the study, did not influence the plasma volume fluctuations. The red blood cell mass, circulating haemoglobin, and total circulating plasma protein varied in the same way and the mean corpuscular haemoglobin concentration also increased during the summer in 2 of the 3 years. The changes in plasma volume are attributed to the influence of environmental temperature and indicate some degree of seasonal acclimatization. Serial measurements of total body water and extracellular space on a few subjects suggest that the seasonal fluctuation affects mainly the vascular system.