Effect of reduced pH in absence of HCO 3− on anomalous and normal potential responses in bullfrog antrum

Abstract

Effect of changing [K +], [Na +] and [Cl −] in nutrient solution on potential difference (PD) and resistance was studied in bullfrog antrum with and without nutrient HCO 3 − but with 95% O 2/5% CO 2 in both cases. In both cases, changing from 4 to 40 mM K + gave about the same initial PD maximum (anomalous response) which was followed by a decrease below control level. Latter effect was much less with zero than with 25 mM HCO 3 −. Changing from 102 to 8 mM Na + gave initial normal PD response about the same in both cases. However, 10 min later the change in PD with zero HCO 3 − was insignificant but with 25 mM HCO 3 − the PD decreased (anomalous response of electrogenic NaCl symport). PD maxima due to K + and Na + were largely related to ( Na + + K +)- ATPase pump. Changes in nutrient Cl − from 81 to 8.1 mM gave only a decrease in PD (normal response). Initial PD increases are explained by relative increases in resistance of simple conductance pathways and of parallel pathways of ( Na + + K +)- ATPase pump and Na +/Cl − symport. Removal of HCO 3 − and concurrent reduction of pH modify resistance of these pathways.