HEMATOLOGICAL AND BODY FLUID ADJUSTMENTS DURING ACCLIMATION TO A COLD ENVIRONMENT

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Abstract
Body fluid volumes and hematological values were compared in rats exposed to air of 6[degree]C for various periods of time and in rats at 30[degree]C for comparable periods. Absolute blood and plasma volumes (T1824 space) decreased with time of exposure to 30[degree]C while extracellular fluid volume (Na space), total body water, and body weight increased. Rats transferred from the warm to the cold environment had larger plasma and blood volumes than those of rats at 30[degree]C after the first week of exposure. After 5 weeks, blood volume was 22% greater on an absolute basis, and 30% greater relative to total body water, than that of the larger rats at 30[degree]C. There were no differences in extracellular fluid volumes between warm and cold exposed rats at comparable intervals. Total water and intracellular water tended to be greater in rats at 30[degree]C on an absolute basis, but they were much greater per unit body weight in rats at 6[degree]C. No differences were seen in red blood cell counts, in hemoglobin concentration, or in. plasma specific gravity between warm and cold exposed rats, but there was an increased hema-tocrit ratio, increased corpuscular volume, and decreased corpuscular hemoglobin content in rats kept at 6[degree]C. Hemoglobin concentration, red cell counts, and plasma specific gravity increased with time in both groups.