STAT3 and cardiac hypertrophy: Figure 6(a) shows the results of a semiquantitative determination of cardiac actin (c-ACT), as a marker of heart hypertrophy. As noted, a significant increase in the amount of this protein was detected after 3 and 4 hours of perfusion in homogenates of these hearts. Such an increase was accompanied by phosphorylation of STAT3 (p-STAT3, Figure 6(b)), a signaling protein that is implicated in the prohypertrophic effect of leptin, but no changes were detected in the total protein (STAT3, panel c).