Receptor-operated, but not voltage-operated, calcium channels are involved in basophil leucocyte activation and histamine release

Transmembrane calcium flux is a critical step in basophil and mast cell activation and subsequent histamine release. This calcium flux is likely to take place through specialized membrane ion channels. Two types of calcium channels have been described so far: the first type is voltage operated and the second type is receptor operated. Depolarization of cell membrane by K⁺-rich solutions is followed by voltage-operated channel opening in excitable cells, such as smooth muscle cells. We evaluated whether high K⁺ extracellular concentrations can trigger basophil activation and histamine release. We found that human basophil leucocytes, showing a normal response to activating signals, such as anti-IgE antiserum and formylmethionine peptide, release no histamine when exposed to K⁺-rich media, alone or in combination with the K⁺ carrier valinomycin. These results are consistent with there being receptor-operated, but not voltage-operated, calcium channels in the basophil leucocyte plasma membrane.