Intracellular pH in the toad Bufo marinus following hypercapnia.

We investigated the effects of hypercapnia on intracellular acid-base regulation in brain and liver of the toad Bufo marinus L. After 1 h at 5% CO2, arterial PCO2 increased significantly, from 1.6 +/- 0.04 to 5.7 +/- 0.23 kPa, while brain and liver intracellular pH (pHi) decreased significantly. Reductions in pHi of both tissues were partially compensated by increased levels of bicarbonate. Surprisingly, however, compensation was lower than expected in brain and higher than expected in liver. We suggest that compensation in brain may be limited by secondary effects of bicarbonate loading in this tissue.