An unusual phosphatidylinositol turnover pathway in noradrenaline-perfused rat hearts.

1. The phosphatidylinositol turnover pathway has been studied in noradrenaline-perfused rat hearts using anion-exchange high performance liquid chromatography. 2. The active calcium-releasing compound inositol-(1,4,5)trisphosphate was detected together with its degradation products inositol-(1,4)bisphosphate and inositol monophosphate. All these products increased in response to noradrenaline stimulation. 3. At noradrenaline perfusion times from 5 s to 20 min there was no appearance of inositol-(1,3,4,5)tetrakisphosphate or its degradation products: inositol-(1,3,4)trisphosphate or inositol-(1,3) and (3,4)bisphosphates. 4. These data suggest the absence of the inositol-(1,4,5)trisphosphate phosphorylation/dephosphorylation pathway in heart.