Résumé
Vasopressin stimulates the liberation of labelled inositol phosphate in partially purified plasma membranes prepared from myo‐[3H]inositol prelabelled WRK1 cells. This stimulatory effect was very rapid (165% stimulation of inositol trisphosphate accumulation after a 10 s incubation period in the presence of 1 μM vasopressin), concentration dependent (EC50= 12 nM) and was abolished by an antagonist of the vasopressor response to vasopressin. GTP, even at high concentrations (0.1 mM), did not increase inositol phosphate release: it was found to be absolutely necessary for hormonal stimulation of phospholipase C activity. Non‐hydrolysable analogues of GTP may also stimulate this enzyme activity.