An isovolumic normal rat heart Langendorff model was used to examine the effects of moderate (15 mmHg) and severe (35 mmHg) mechanical stretch on the time course (from 0 to 60 min) of myocardial expression of tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, and insulin-like growth factor (IGF)-1 and their cognate receptors. After 10 min of moderate stretch, TNF-alpha was de novo expressed, whereas constitutive IL-6 and IGF-1 levels were slightly upregulated; no further changes occurred up to 60 min. In comparison, severe stretch resulted in a higher and progressive increase in TNF-alpha, IL-6, and IGF-1 expression up to 20 min. After 20 min, whereas TNF-alpha expression further increased, IL-6 and IGF-1 levels progressively reduced to values lower than those observed under moderate stretch and in unstretched (5 mmHg) control myocardium (IL-6). Mechanical stretch did not significantly alter the expression of the cognate receptors. Indeed, the TNF-alpha receptor (p55) tended to be progressively upregulated under severe stretch over time. The current data provide the first demonstration that TNF-alpha, IL-6, and IGF-1 ligand-receptor systems are differentially expressed within the normal rat myocardium in response to graded mechanical stretch. Such findings may have potential implications with regard to compensatory hypertrophy and failure.