Effect of prolonged cold exposure on the gross blood composition of the rat

¹ Physiology Branch, Arctic Aeromedical Laboratory, APO 731, Seattle, Washington

One month's cold exposure (5 ± 1 °C) of male Sprague-Dawley rats induced a slight, but significant, increase in hemoglobin levels but had no effect on the hematocrit. Fasting for 24 hours, although not altering the hemoglobin concentrations of either the control or the cold-exposed animals, did produce a slight lowering of the hematocrit. Cold exposure also resulted in a plasma dilution as indicated by a significant increase in plasma water, and significant decreases in plasma specific gravity and plasma protein levels. Fasting superimposed a further reduction in plasma protein levels under both control and cold-exposed conditions. The levels of blood glucose and total plasma lipids were unaltered by cold exposure but each was significantly reduced by fasting. Significant increases in the nonprotein nitrogen, phospholipid, cholesterol and ketone levels were observed in cold-exposed, nonfasted animals. Superimposed on these changes, fasting produced a decrease in the levels of nonprotein nitrogen and phospholipids and an increase in the level of ketones. It had no effect on the level of cholesterol. Fasting of the cold-exposed animals led to greater reductions in plasma nonprotein nitrogen and phospholipids and a smaller increase in blood ketones as compared to controls.