Fibroblast growth factor-2 stimulates phospholipase C beta in adult cardiomyocytes

Although fibroblast growth factor-2 (FGF-2) plays an important role in card ioprotection and growth, little is known about the signals triggered by it in the adult heart. We therefore examined FGF-2-induced effects on phosphoi nositide-specific phospholipase C (PI-PLC) isozymes, which produce second m essengers linked to the inotropic and hypertrophic response of the myocardi um. FGF-2, administered by retrograde perfusion to the isolated heart, indu ced an increase in inositol-1,4,5-trisphosphate levels in the cytosol, as w ell as an increase in total PI-PLC activity associated with sarcolemmal and cytosolic fractions. Furthermore FGF-2 induced a time-dependent elevation in cardiomyocyte membrane-associated PLC gamma1 and PLC beta 1 activities, assayed in immunoprecipitated fractions, and moreover, increased the membra ne levels of PLC beta 1 and PLC beta 3. Activation of PLC beta is suggestiv e of FGF-2-induced cross-talk between FGF-receptor tyrosine kinase and G-pr otein-coupled signaling in adult cardiomyocytes and underscores the importa nce of FGF-2 in cardiac physiology.