Seasonal changes in human body fluids.

It is well-known that the blood properties change with seasons, and especially many reports in respect to change in water content have been made. For example, Kuroda (1) reported that the water content in blood increases in summer, while it decreases in winter. The fact can be explained by the view of Bazett (2), Sjostrand (3), Yoshimura and others (4) that the circulating blood volume, especially its plasma volume, increases in summer, while it decreases in winter. The first demonstration of the relationship between climate and blood volume was provided by Barcroft et al. (5) who were sailing from England to Peru across the equator. This increase of blood volume was attributed by previous authors to the increase of vascular bed which expands in hot climate by dilatation of cutaneous vessels (6). On the other hand, Forbes, Dill and Hall (7) and recently Doupe (8) failed to confirm the findings of Barcroft. Bass and Henschel (8) expressed their opinion in their excellent review on climatic changes of body fluids that the lack of general agreement regarding seasonal variations in body fluids is not surprising in view of the confounding variables in these investigations. Recently, the author (4) pointed out influencial effects of seasonal alteration of water metabolism upon body fluids which may reflect on blood volume. Little work has ever been done on the interrelation of seasonal changes in body fluid compartments with water metabolism. Moreover, the previous reports on climatic changes of body fluids are quite conflicting as was pointed out by Bass and Henshel (8), and further investigations under well controlled experimental conditions are required. The present study was planned firstly to verify seasonal variations in amount and distribution of water and salts of body fluids in human subjects by repeating monthly measurements of body fluids a basal condition. The second aim was to observe seasonal changes of water metabolism under well controlled experimental conditions and to elucidate its possible effects upon body fluid compartments and blood properties.