Culturing rat neonatal myocytes causes changes in the phosphatidylinositol turnover pathway

1. Cultured neonatal myocytes are commonly used as a model system for the study of cardiac phosphatidylinositol (PI) turnover. 2. In neonatal myocytes stimulation with noradrenaline causes the release of the Ca2(+)-releasing compound inositol-1,4,5-trisphosphate and the generation of the Ca2(+)-regulatory compound inositol-1,3,4,5-tetrakisphosphate. 3. Addition of noradrenaline to intact, neonatal rat hearts stimulates the release of inositol-1,4,5-trisphosphate, but not inositol-1,3,4,5-tetrakisphosphate. 4. These findings show that the isolation and culture of the neonatal myocyte causes changes in the PI turnover pathway so that it becomes similar to that described in other cell types and different from that in intact myocardial tissue. 5. The neonatal myocyte is not a useful model for the study of cardiac PI turnover.