Hormone-mediated inositol lipid breakdown in hepatocytes and WRK1 cells: relationship to receptor function

All hormones and neurotransmitters which provoke their intracellular effects by increasing the cytosolic concentration of Ca²⁺ in their target cells also stimulate the breakdown of inositol phospholipids. Much evidence suggests that this breakdown is intimately involved in the mechanism which couples cell-surface receptor activation to intracellular Ca²⁺ mobilization. Recent results indicate that the primary, receptor-mediated event in stimulated cells is a phosphodiesteric hydrolysis of phosphatidylinositol 4,5-bisphosphate to yield inositol trisphosphate and diacylglycerol. It is likely that both products of this reaction fulfill 'second messenger' roles within stimulated cells.