Effect of insulin on the phospholipase-D activity of untreated and insulin-pretreated (hormonally imprinted) Tetrahymena

Insulin treatment of the unicellular Tetrahymena enormously increases the activity of phospholipase D (PLD) within 30 min. Insulin pretreatment (hormonal imprinting) does not influence basal PLD activity after 24 h. The second insulin treatment failed to stimulate PLD activity in insulin imprinted Tetrahymena. The results suggest the presence of the functional PLD activity in Tetrahymena and that hormonal imprinting modifies signal transduction to PLD, as previously reported in calmodulin activation and phophatidylinositol 4,5-bis-phosphate (PIP2) synthesis.