Studies from both in vivo and in vitro model systems have provided an initial skeleton of the potential signaling pathways that might regulate cardiac genes during growth and hypertrophy. One of the first detectable changes in cardiac gene expression is the activation of a program of immediate early gene expression, which is distinct for the hypertrophic response, and is conserved in multiple models of both in vivo and in vitro hypertrophy. Diverse and distinct hormonal stimuli have been documented to activate several features of the hypertrophic response, including several autocrine and paracrine factors. Although the signaling mechanisms that link these factors with the activation of cardiac gene expression are unclear, recent studies suggest that the activation of protein kinase C may represent one of the most proximal common events in this signaling cascade. The activation of cardiac target genes induces a program of embryonic gene expression, including the atrial natriuretic factor (ANF) gene. The ci...