Water and Electrolyte Exchange during Exposure to Cold, Altitude and Combined Cold and Altitude

摘要

Exposure of rats to air at 5 C for 1 to 12 days is accompanied by a relative dehydration in spite of the continued presence of water. Dehydration was manifested by: (a) a reduction in the ration of water/food ingested; (b) an increase in the ratio of urine excreted/water ingested; (c) an increased evaporative water loss; (d) an increased serum osmolality and chloride concentration; and (c) a striking thirst and ingestion of water following transfer from cold to air at 26 C. Drinking began within 15 minutes and lasted approximately 1 hour. Thermogenic drinking persisted for at least 120 days of exposure to cold. It was not thwarted by preventing access to water for either 1 or 2 hours following transfer to warm air, but either intragastric or intraperitoneal administration of a water load equal to 3% of body weight inhibited water intake following transfer. Rats exposed chronically to hypoxia (12% oxygen in nitrogen) became dehydrated. They decreased their water intake below prehypoxic control levels during the first 2 weeks of exposure but gradually returned water intake to control level by the 4th week of exposure. In contrast, daily urinary output was uninfluenced by hypoxia.