Intracellular pH changes during experimental sustained hypercapnia

During various time periods lasting 3--28 days rats were continuously exposed to FICO2 = 0.08 or 0.16 in normoxic conditions, pHi was measured by the 3H-inulin and 14C-DMO method in the erythrocyte, the gastrocnemius and in the whole body. The erythrocyte acid base disturbances were linked to the extracellular acidosis. The muscle and the mean body pHi developments were the same during 9 or 14 days depending on the FICO2. They diverged after 28 days at FICO2 = 0.08 (Tables and Fig. 2). This could be explained as an acid base reaction of the "non-muscular" part of the whole body intracellular compartment which may be different from the acid base development of the muscular mass. A short term (1 h) acute hypercapnia (FICO2 - 0.20--0.22) was superimposed on the sustained hypercapnia (FICO2 = 0.16). Acid base disturbance was greater when the acute hypercapnia was added at the beginning (3rd day) of the CO2 exposure (Fig.1).