CA2-ACTIVATED OUTWARD-RECTIFIER K+ CHANNELS AND HISTAMINE-RELEASE BY RAT GASTRIC ENTEROCHROMAFFIN-LIKE CELLS()

Gastric enterochromaffin-like (ECL) cells were isolated from rat gastr ic fundic mucosa by Percoll density-gradient centrifugation and counte r-flow elutriation. About 67% of cells in the purified cell suspension were ECL cells, which were reacted with anti-histidine decarboxylase antibody. A23187, a calcium ionophore, at 0.1-10 mu M induced histamin e release from the ECL cell-rich suspension, indicating that the Ca2pathway is involved in the mechanism of histamine release from ECL cel ls. A23187 at 5 mu M significantly increased outward-rectifier cationi c current in 62% of cells in the ECL cell-rich fraction. A23187-sensit ive cells showed acridine orange uptake. In single-channel recordings, a Ca2+-dependent outward-rectifier K+ channel of large conductance (1 46 +/- 22 picosiemens) was found in the cell that showed acridine oran ge uptake. The channel opened in a voltage-dependent manner at 0.1 mu M of intracellular free Ca2+ concentration. These results may suggest that opening of the Ca2+-activated K+ channel is one of the steps invo lved in the mechanism of histamine release in ECL cells.