Do Humoral and Mechanical Stimulation of Cardiomyocytes Share Common Transduction Pathways

Physical forces are the most basic and non-specific forces to which living organisms were exposed during evolution, whereas humoral effectors developed in more complex organisms. We tested the hypothesis that both adrenergic (humoral) and hypergravity (mechanical) stimulation may share common signal transduction pathways. Mechanical loading remains the most critical effector in the development of cardiac hypertrophy, while hypergravity is currently used to train aircraft and space crews and may lead to aberrations in cardiac function. In this study, we used cultured cardiomyoctes submitted to 10 min hypergravity or to adrenostimulation. Specific inhibitors of adrenoreceptors and of protein kinases were used to identify cell reactivity. The mRNA of c-fos and creatine kinase isoenzymes was determined by Northern blot. We showed that with respect to c-fos induction, although both effectors are initiated at different transduction levels, apparently share a common transduction pathway—Protein kinase C—but in reality they are transduced via different isoenzymes of the PKC complex. Creatine kinase is expressed through two independent pathways. We suggest that studying the opposite effects of hypo- and hypergravity could add new insights into how cells sense mechanical stimulation that might lead to identification of the cellular messengers participating in the mechanosensitive pathways.