Acidic fibroblast growth factor inhibits junctional communication of Schwann cells in culture

The effect of acidic fibroblast growth factor (aFGF) was investigated on ju nctional communication of rat Schwann cells (SC) in culture. As measured by dye transfer the incidence of coupling between SC was very low during the phase of proliferation and increased slowly and progressively with time und er culture conditions that induced the myelinating phenotype. Treatment wit h aFGF alone or in combination with heparin decreased markedly coupling bet ween SC in both culture stages. The coupling inhibition was rapid, the earl iest effects being apparent 5-15 min after addition of growth factor and wa s transient with a slower recovery of coupling at 1-3 h. The uncoupling eff ect of aFGF could be prevented by an inhibitor of protein-tyrosine kinase. Addition of heparin to cultures decreased the most effective aFGF concentra tion by 100-fold, from 100 ng ml(-1) to 1 ng ml(-1). The dose-response curv es exhibited a characteristic window-shape. The results suggest that FGF mi ght be involved in the regulation of the junctional communication between r at SC via tyrosine kinases.