Characterization of a voltage-dependent conductance in the basolateral membrane of leech skin epithelium.
Voltage clamp studies were performed on the dorsal integument of Hirudo medicinalis. Under apical calcium-free conditions an inward-directed component of transepithelial current was activated by changes of transepithelial voltage. Depolarization caused up to 50% increase of the transepithelial sodium current. Hyperpolarization had no comparable effects. With calcium (1.8 mM) or amiloride (100 microM) in the apical solution and in sodium-free solutions the inward-directed current failed to increase after depolarization. Activation also occurred under chloride-free conditions. Permeabilization of the apical membrane by nystatin (5 microM) increased the current activation significantly. After nystatin, calcium as well as amiloride lost their inhibitory effects. This indicates a basolateral localization of the voltage-dependent conductance. Vesicle insertion or cytoskeletal structures are probably not involved in regulation, as seen by the lack of effects of brefeldin A and the cytochalasins B and D. However, serosal hyposmolar solutions (170 mosmol.1(-1)) caused a reinforced activation of the current. Our results indicate a voltage-dependent conductance in a tight sodium-absorbing epithelium.
Schnizler
M
M
Institut für Tierphysiologie, Justus-Liebig-Universität Giessen, Germany.
Clauss
W
W
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D020126:Brefeldin A; D002118:Calcium / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology; D003517:Cyclopentanes / Q000494:pharmacology; D003572:Cytochalasins / Q000494:pharmacology; D004553:Electric Conductivity; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology; D007865:Leeches / Q000502:physiology*; D009761:Nystatin / Q000494:pharmacology; D009994:Osmolar Concentration; D018408:Patch-Clamp Techniques; D012879:Skin Physiological Phenomena; D015222:Sodium Channels / Q000187:drug effects / Q000502:physiology
D000900:Anti-Bacterial Agents; D003517:Cyclopentanes; D003572:Cytochalasins; D007473:Ion Channels; D015222:Sodium Channels; D009761:Nystatin; D020126:Brefeldin A; D000584:Amiloride; D002118:Calcium