[Inositol triphosphate: a new class of intracellular second messenger].

Hormones, neurotransmitters and other signaling molecules that mobilize intracellular calcium stimulate the activity of the phospholipase C. This enzyme specifically hydrolyses the phosphoinositides and leads to the generation of two second messengers: the inositol triphosphate which mobilizes calcium from the endoplasmic pools and the diacylglycerol which stimulates the protein kinase C. The integration of these two metabolic pathways lead to the biological effect associated to the hormone or the neurotransmitter considered. In this review we will focussed our attention on the first step of these transducing mechanisms: the receptor-mediated hydrolysis of phosphoinositides.