Organ fluid changes and electrolyte excretion of rats exposed to high altitude

Electrolyte balances, serum electrolyte concentrations, and fluid changes in the liver, spleen, kidney, heart, and brain of albino rats were studied at Denver (1620 m) and Pike's Peak (4300m), in Colorado. Control animals were subjected to pair feeding and equal transportation stress. Animals were sacrificed after 2, 4, 6, 8, 10, and 12 h, and 1, 2, 3, 6, 9, and 12 d of exposure. There was no significant growth depression after the first 24 h at altitude. The water content of all tissues were increased during the first day of exposure. Liver showed an increased percent dry weight following 1 d, possibly due to an increase in fat content. Serum Na plus concentrations were significantly increased throughout the 12 d of exposure while K plus was decreased. Hematocrit and hemoglobin values were immediately increased at altitude with the RBC count being significantly higher by Day 9. Altitude rats retained more Na plus, K plus, Ca plus plus, and Mg plus plus than controls, with K plus and Ca plus plus showing the highest retention. The data indicated a shift of fluids from the extra- to the intracellular compartment, especially during the first 12 h of exposure.