bFGF promotes functional expression of transient outward currents in cultured neonatal rat ventricular cells

To investigate the effect of basic fibroblast growth factor (bFGF) on ion channel expressions in developing cardiac cells, a short-term primary culture of ventricular myocytes isolated from day-old newborn rats was established. Functional expressions of the transient outward currents (Ito) were measured by whole-cell voltage-clamp method. Addition of 40 ng/ml bFGF to the serum-free culture medium for 72 hours increased the Ito density without influences on membrane capacitance of the myocytes, an estimate of cell size. bFGF also promoted expressions of the steady-state outward currents. Methyl 2,5-dihydroxycinnamate (3 microM), a tyrosine kinase inhibitor, showed preferential inhibition of the bFGF-stimulated increase in Ito density. These results suggest that bFGF may play a role in regulating ion channel expressions of developing cardiac cells via activation of bFGF receptor tyrosine kinase activity.