BFGF PROMOTES FUNCTIONAL EXPRESSIONS OF TRANSIENT OUTWARD CURRENTS INCULTURED 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 prim ary culture of ventricular myocytes isolated from day-old newborn rats was established, Functional expressions of the transient outward curr ents (I-to) were measured by whole-cell voltage-clamp method. Addition of 40 ng/ml bFGF to the serum-free culture medium for 72 hours increa sed 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 mu M), a tyrosine kinase inhibitor, showed preferential inhibition of th e bFGF-stimulated increase in I-to density. These results suggest that bFGF may play a role in regulating ion channel expressions of develop ing cardiac cells via activation of bFGF receptor tyrosine kinase acti vity.