Kasbekar D K
Am J Physiol. 1986 Jun;250(6 Pt 1):G765-72. doi: 10.1152/ajpgi.1986.250.6.G765.
Transmural potential difference (PD) and resistance (R) changes after luminal or serosal instillation of K+ were determined under various conditions in chambered preparations of frog gastric mucosae. Potassium selectivity of the luminal membrane is indicated by the rapid reversal of the inverted PD of mucosae bathed in NaCl-free, choline sulfate (Ch2SO4)-Ringer on the serosal side and unbuffered hypertonic Ch2SO4 solution on the luminal side on luminal K+ instillation. The delta PD responses are significantly attenuated, however, in histamine-stimulated mucosae bathed in hypotonic or in burimamide-inhibited mucosae bathed in hyper- and hypotonic luminal media, which suggests that the K+ selectivity of the luminal membrane resides largely in the tubular cell apical membrane. Imposing a serosal-to-luminal transmucosal K+ gradient in both histamine-stimulated and omeprazole-inhibited mucosae also reversed the normal orientation of PD but not in those inhibited with burimamide. In the latter, the PD inversion was attenuated but maintained its normal orientation. These data suggest that burimamide, but not omeprazole, acts by blocking luminal membrane K+ conductance. The inverted PD in mucosae bathed in Cl-free media may thus be due partially or fully to K+ diffusion driven by the cell-to-lumen K+ gradient via the luminal K+ conductance pathway. These findings have implications for the controversy surrounding the postulated electrogenicity of the gastric proton pump.
在蛙胃黏膜的腔室制备物中，在各种条件下测定了腔内或浆膜内注入钾离子（K⁺）后的跨壁电位差（PD）和电阻（R）变化。当向腔内注入K⁺时，在浆膜侧用无氯化钠、硫酸胆碱（Ch₂SO₄）-林格液，腔内用无缓冲的高渗Ch₂SO₄溶液灌流的黏膜中，腔内膜的钾选择性表现为黏膜反转PD的快速逆转。然而，在组胺刺激的黏膜中，用低渗溶液灌流时，以及在布立马胺抑制的黏膜中，用高渗和低渗腔内介质灌流时，δPD反应明显减弱，这表明腔内膜的K⁺选择性主要存在于管状细胞顶端膜。在组胺刺激的和奥美拉唑抑制的黏膜中施加从浆膜到腔内的跨黏膜K⁺梯度，也会使PD的正常方向逆转，但在布立马胺抑制的黏膜中则不会。在后者中，PD反转减弱但仍保持其正常方向。这些数据表明，布立马胺而非奥美拉唑，是通过阻断腔内膜K⁺电导起作用的。因此，在无氯介质中灌流的黏膜中的反转PD可能部分或完全归因于通过腔内K⁺电导途径由细胞到管腔的K⁺梯度驱动的K⁺扩散。这些发现对于围绕胃质子泵假定的电生性的争议具有启示意义。
