Evidence for a K+Channel Requirement in Spreading of Rat Basophilic Leukemia Cells on Fibronectin-Coated Surfaces

We investigated the ionic requirements for the early events of cell–extracellular matrix interactions leading to cell spreading. We found that potassium ions were required specifically in several cell types. Adhesion to fibronectin- (FN) coated surfaces was independent of K+in the medium. In contrast, cells that adhered to FN in the absence of K+failed to spread. This requirement for K+occurred only during a discrete time frame: in the first 15 minutes following adhesion. Moreover, we identified a specific trans-membrane flux of the radioactive K+analog86Rb+, the kinetics of which correlated with this requirement. Both this ion flux and cell spreading were blocked by the K+-channel inhibitors tetraethylammonium (TEA) and 4-aminopyridine (4-AP). Our results suggest that this K+ion flux and the channels that regulate it are important in regulating the initial responses to adhesion that lead to spreading.