Effect of reduced pH in absence of HCO3(-) on anomalous and normal potential responses in bullfrog antrum.
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 HCO3(-) but with 95% O2/5% CO2 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 HCO3(-). 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 HCO3(-) was insignificant but with 25 mM HCO3(-) 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 HCO3(-) and concurrent reduction of pH modify resistance of these pathways.
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002712:Chlorides / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D008954:Models, Biological; D011188:Potassium / Q000494:pharmacology; D011706:Pyloric Antrum / Q000502:physiology*; D011892:Rana catesbeiana; D012964:Sodium / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013816:Thermodynamics
D001639:Bicarbonates; D002712:Chlorides; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium