Mn-stimulated adhesion and spreading of Ehrlich ascites cells are separate processes

Mn2+ is extremely effective in stimulating both the adhesion and spreading of Ehrlich ascites tumour (EAT) cells on plastic surfaces. Trifluoperazine (TFP), a calmodulin antagonist, inhibited Mn2+induced cell spreading but did not affect cell-substrate adhesion, indicating that Mn2+-stimulated adhesion of EAT cells was not dependent on the ability of the cation to promote cell spreading, but was due to a direct effect on the attachment process. Mn2+ was shown to be highly effective as a cofactor for fibronectin-mediated adhesion of EAT cells which may account for its ability to stimulate adhesion in the absence of cell spreading.