Schwartz M, Carrasquer G, Rehm W S
Biochim Biophys Acta. 1984 Jan 11;769(1):105-16. doi: 10.1016/0005-2736(84)90014-2.
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.
在含有和不含HCO₃⁻的营养液中，研究了改变牛蛙胃窦营养液中[K⁺]、[Na⁺]和[Cl⁻]的影响。在25 mM HCO₃⁻（95% O₂/5% CO₂）和零HCO₃⁻（100% O₂）条件下，营养液pH维持在7.3。将K⁺从4 mM变为40 mM或Cl⁻从81 mM变为8.1 mM，10分钟后跨黏膜电位差降低（营养液变得更负）——这是正常反应。在零HCO₃⁻条件下这些反应比在25 mM HCO₃⁻条件下小。将Na⁺从102 mM降至8 mM会降低电位差（电中性NaCl同向转运体的异常反应）。在零HCO₃⁻条件下这种效应减弱或消除。相比之下，将K⁺从4 mM变为40 mM会产生初始异常的电位差反应，将Na⁺从102 mM变为8 mM，在零或25 mM HCO₃⁻条件下会产生初始正常的电位差反应。这两种反应都与（Na⁺ + K⁺）-ATP酶泵有关，且在零HCO₃⁻条件下比在25 mM HCO₃⁻条件下更大。零HCO₃⁻条件下初始电位差增加被解释为由于被动电导和/或NaCl同向转运体途径的电阻增加。因此，去除HCO₃⁻会改变营养液膜的电导途径。
