WHOLE-CELL POTASSIUM CURRENTS IN FETAL-RAT ALVEOLAR TYPE-II EPITHELIAL-CELLS CULTURED ON MATRIGEL MATRIX

Patch-clamp studies were performed on fetal rat alveolar type II cells isolated at 19 days of gestation and cultured on either plastic for 7 days or Matrigel matrix (40-50 mu l/cm(2)) for 10 days. Before study, cells cultured on Matrigel matrix were dissociated from alveolar-like structures with enzymes, replated, and washed with cold buffer at a c onstant flow rate to remove residual gel. This wash significantly impr oved obtaining of successful seals. Potassium current-voltage relation ships and maximum whole cell K+ conductance (normalized to membrane ca pacitance) were significantly changed with time in cells cultured on p lastic, but no significant change occurred in cells cultured on Matrig el matrix. Application of 20 mM tetraethylammonium, 2 mM 4-aminopyridi ne, and 5 mM BaCl2 significantly inhibited K+ currents, showing differ ences in channel sensitivity to these agents and a voltage-dependent b lockage between culture groups or with time in culture. To conclude, w e have developed a new method by which epithelial cells cultured on Ma trigel matrix can be successfully studied with the use of patch-clamp techniques. Furthermore, these studies show that fetal type II cells h ave voltage-activated K+ channels and that channel density and their s ensitivity to channel blockers are modulated by the substratum on whic h the cells are cultured.