Potential difference responses due to K+, Na+ and Cl- changes in bullfrog antrum with and without HCO3-.
The effect of changing [K+], [Na+] and [Cl-] in nutrient solution was studied in bullfrog antrum with and without HCO3- in nutrient. In 25 mM HCO3- (95% O2/5% CO2) and in zero HCO3- (100% O2), nutrient pH was maintained at 7.3. Changing from 4 to 40 mM K+ or from 81 to 8.1 mM Cl- gave a decrease 10 min later in transmucosal PD (nutrient became more negative)--a normal response. These responses were less in zero than in 25 mM HCO3-. A decrease from 102 to 8 mM Na+ decreased PD (anomalous response of electrogenic NaCl symport). This effect was attenuated or eliminated in zero HCO3-. In contrast, change from 4 to 40 mM K+ gave initial anomalous PD response and change from 102 to 8 mM Na+, initial normal PD response with either zero or 25 mM HCO3-. Both responses were associated with (Na+ + K+)-ATPase pump and were greater in zero than in 25 mM HCO3-. Initial PD increases in zero HCO3- are explained as due to increase in the resistance of passive conductance and/or NaCl symport pathways. Thus, removal of HCO3- modifies conductance pathways of nutrient membrane.
D000818:Animals; D001639:Bicarbonates / Q000502:physiology; D002712:Chlorides / Q000502:physiology*; D004553:Electric Conductivity; D008564:Membrane Potentials; D011188:Potassium / Q000502:physiology*; D011706:Pyloric Antrum / Q000502:physiology*; D011892:Rana catesbeiana; D012964:Sodium / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D001639:Bicarbonates; D002712:Chlorides; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium