EFFECTS OF CHRONIC HYPERCAPNIA ON ELECTROLYTE AND ACID-BASE EQUILIBRIUM. III. CHARACTERISTICS OF THE ADAPTIVE AND RECOVERY PROCESS AS EVALUATED BY PROVISION OF ALKALI*

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Abstract
After induction of hypercapnia (12% CO2) in dogs provided with 5.5 to 6.5 m[image] of NaHCO3-/KgBw, plasma [HCO3-] did not reach its maximal level of approximately 36 mEq/l for 3 to 4 days. These data suggest that a constant elevation of pCO2 induces a slow adaptive process that is responsible for the progressive increase in the capacity of the kidney to completely reabsorb HCO3". This pattern of rise in plasma [HCO3- ] is similar to that previously observed in animals on an alkali-free intake; since the animals in these earlier studied excreted an almost bicarbonate-free urine, it appears that in chronic hypercapnia the rate of HCO3- generation by the kidney and the rise in HCO3" threshold are closely linked. After the animals were returned to room air, plasma [HCO3" ] fell to approximately 30 mEq/1. Acid-base equilibrium was subsequently restored to normal when Cl was administered as either the Na or K salt, despite a continued high alkali intake.