Tissue carbon dioxide concentrations in rats during acute respiratory acidosis

Abstract

Tissue carbon dioxide concentrations were measured in rats following exposure of the intact animals to 10% or 30% Co2 in oxygen for time intervals from 5 minutes to 2.5 hours. The rats were sacrificed by decapitation. The average normal Co2 concentrations in skeletal muscle, heart and brain were 13.2, 18.6 and 15.1 mm/kg of wet tissue, respectively. The tissue Co2 increased at about the same rate, relative to normal concentration, in each of the three tissues, the concentration approximately doubling in the first 35 minutes on 30% Co2. The skeletal muscle Co2 concentration on 30% Co2 followed a single exponential curve in which the rate constant was 0.036 min.-1. Tissue Co2 capacity curves and data on the rate of Co2 loss post mortem are presented. The barium-soluble Co2 fraction of Conway and Fearon was found to increase in skeletal muscle from 9.4 to 14.6 mm/kg wet tissue when rats had been on 30% Co2 for 1 hour. Even in control rats this fraction showed a large variability and may have little physiological significance. Submitted on April 23, 1959