Stress response in chronic hypercapnia

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Abstract
Respiratory acidosis induced by prolonged exposure of guinea pigs to 15% COo in 21% 02 was compensated after 3 days exposure. Adrenal cortical response measured by a rise of blood corticosteroids, adrenal cholesterol depletion, and lymphopenia was limited to the 3-day phase of uncompensated respiratory acidosis. The same was true for adrenal medullary stimulation as indicated by adrenal epinephrine depletion. Free fatty acid levels did not change during the 1st hr of exposure to 15% CO2,, but showed a 100% rise after 6 hr of exposure and returned to initial levels with the compensation of the respiratory acidosis. Intermittent daily 8-hr exposure to 15% COo for 7 days did neither produce a compensation of the respiratory acidosis nor an abatement of the sympathoadrenal stimulation. Significant changes in body weight consisting in a 10% loss occurred only during the first 2 days of exposure to 15% CO2. Adrenal enlargement and lymphatic involution accompanying the sympathico-adrenal response to respiratory acidosis outlasted the functional changes and were still present after 7 days of exposure to 15% CO2.