Serum enzyme changes in dogs exposed repeatedly to severe altitude hypoxia

¹ Laboratories of Experimental Pathology and Physical Biology, National Institute of Arthritis and Metabolic Diseases, National Institutes of Health, Bethesda, Maryland

Blood values were determined on dogs exposed to a simulated altitude of 32,000 ft for 4 hr five times weekly for 7 weeks. Serum glutamic oxalacetic transaminase and serum lactic dehydrogenase values showed a gradual increase during the 7 weeks, while serum glutamic pyruvic transaminase values stabilized by the 2nd week at slightly above initial normal values. Serum alkaline phosphatase and serum aldolase values stabilized after the 3rd week at two to three times the initial values. After cessation of exposures, values dropped sharply during the first 2 weeks and slowly approached normal values at the end of 6 weeks. A subsequent single 4-hr exposure to 32,000 ft evoked the usual transient sharp rise in serum enzyme values, but not the typical hyperglycemic response, observed before the acclimatization. Terminal pathologic studies revealed minor residual lesions, attributable to the repeated exposures, which may account in part for the slow restoration of normal values after cessation of exposures.