Quantitative determination of gap junction intercellular communication using flow cytometric measurement of fluorescent dye transfer.

Gap junction intercellular communication (GJIC) is involved in several aspects of normal cell behaviour, and disturbances in this type of communication have been associated with many pathological conditions. Reliable and accurate methods for the determination of GJIC are therefore important in studies of cell biology. (Tomasetto, C., Neveu, M.J., Daley, J., Horan, P.K. and Sager, R. (1993) Journal of Cell Biology, 122, 157-167) reported some years ago the use of flow cytometer to determine transfer between cells of a mobile dye, calcein, as a measure of cell communication through gap junctions. In spite of this being a method with potential for quantitative and reliable determination of GJIC, it has been modestly used, possibly due to technical difficulties. In the present work we have illustrated several ways to use flow cytometric data to express cell communication through gap junctions. The recipient cells were pre-stained with the permanent lipophilic dye PKH26, and the donor cell population were loaded with the gap junction permeable dye, calcein. We show that the method may be used to measure the effect of chemicals on GJIC, and that the information is reliable, objective and reproducible due to the large number of cells studied. The data may give additional information to that obtained with other methods, since the effect observed will be on the establishment of cell communication as compared to what is observed for microinjection or scrape loading, where the effect is on already established communication. This is probably the reason for the more potent effects of DMSO on GJIC measured by the present method than on already existing GJIC measured by microinjection or quantitative scrape loading. We also show that the problem related to the mobile dye calcein not being fixable with aldehydes will not affect the results as long as the cells are kept on ice in the dark and analysed by flow cytometer within the first hours after formalin cell fixation.