Actions of anabolic hormones and growth factors on cultured neonatal heart cells.

The effects of a series of major anabolic hormones on incorporation of labeled precursors into protein and DNA were measured in cardiac myocytes from neonatal rats. IGF-I, TGF beta, and insulin all stimulated [3H] leucine incorporation into protein; FGF, EGF, triiodothyronine and dexamethasone had little or no effect. The effect of insulin was biphasic, suggesting some stimulation mediated directly by the insulin receptor and some by cross-reaction with the IGF-I receptor. Only IGF-I caused substantial stimulation of [3H] thymidine incorporation; small effects of TGF beta, FGF and insulin were also seen. In both kinds of measurements, combinations of these hormones gave greater stimulation than was obtained with individual proteins. Possible contribution to observed effects by contaminating fibroblasts was evaluated and eliminated. We conclude that cardiac myoblasts respond to a similar range of anabolic agents that have previously been observed for skeletal and smooth muscle.