Biochemistry of Submarine and Diving Stress. 1. Lactate-Pyruvate and Redox State Responses of Blood and Tissue in Chronic Hypercapnia
NAVAL SUBMARINE MEDICAL RESEARCH LAB GROTON CT
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Lactate and pyruvate concentrations were measured in blood and various tissues of guinea pigs exposed to 15 CO2 in 21 O2, balance N2, for varying periods of time up to one week. Acute exposure resulted in reduction of lactatepyruvate ratios LP of blood, heart, and muscle but not liver. Blood LP further decreased after one day of exposure and slowly increased during the chronic phase of respiratory acidosis. Heart LP returned to control values by six hours while muscle LP remained depressed for the duration of hypercapnia. Since LP reflect the redox state of the free glycolytic nicotinamide-adenine dinucleotide couplet, the redox state, NADNADH was calculated from the LP and pH of blood for the various periods of hypercapnia. During acute hypercapnia NADNADH increased in blood markedly indicating the existence of a more oxidized state during this period. Chronic hypercapnia returned blood NADNADH toward initial values suggesting a normalization of glycolytic metabolism. The observed differences in LP in the various tissues are apparently related to the different CO2 buffering capacities of tissues.
- Stress Physiology