Beta-adrenergic receptor (beta-AR) stimulation induces apoptosis in adult rat ventricular myocytes (ARVMs) via the activation of glycogen synthase kinase-3beta (GSK-3beta) and mitochondrial pathways. However, beta-AR stimulation induces apoptosis only in a fraction ( approximately 15-20%) of ARVMs. We hypothesized that ARVMs may secrete/release a survival factor(s) which protects 80-85% of cells from apoptosis.