title: Implications of an anomalous intracellular electrical response in bullfrog corneal epithelium.
abstract: The ionic dependencies of the transepithelial and intracellular electrical parameters were measured in the isolated frog cornea. In NaCl Ringer's the intracellular potential difference Vsc measured under short-circuit conditions depolarized by nearly the same amount after either increasing the stromal-side KCl concentration from 2.5 to 25 mM or exposure to 2 mM BaCl2 (K+ channel blocker). With Ba2+ the depolarization of the Vsc by 25 mM K+ was reduced to one-quarter of the control change. If the Cl-permselective apical membrane resistance Ro remained unchanged, the relative basolateral membrane resistance Ri, which includes the lateral intercellular space, increased at the most by less than twofold after Ba2+. These effects in conjunction with the depolarization of the Vsc by 62 mV after increasing the stromal-side K+ from 2.5 to 100 mM in Cl-free Ringer's as well as the increase of the apparent ratio of membrane resistances (a = Ro/Ri) from 13 to 32 are all indicative of an appreciable basolateral membrane K+ conductance. This ratio decreased significantly after exposure to either 25 mM K+ or Ba2+. The decline of Ro/Ri with 25 mM K+ appears to be anomalous since this decrease is not consistent with just an increase of basolateral membrane conductance by 25 mM K+, but rather perhaps a larger decrease of Ro than Ri. Also an increase of lateral space resistance may offset the effect of decreasing Ri with 25 mM K+. In contrast, Ro/Ri did transiently increase during voltage clamping of the apical membrane potential difference Vo and exposure to 25 mM K+ on the stromal side.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001464:Barium / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003315:Cornea / Q000502:physiology*; D004553:Electric Conductivity / Q000187:drug effects; D004848:Epithelium / Q000502:physiology; D007700:Kinetics; D011188:Potassium / Q000378:metabolism; D011189:Potassium Chloride / Q000494:pharmacology; D011892:Rana catesbeiana
chemical_list: D001464:Barium; D011189:Potassium Chloride; D011188:Potassium