Thyrotropin releasing hormone (TRH) accelerates the turnover of phosphatrdylinosrtol m GH3 cells ('phospholiprd response') From the analysis of inositol phosphates m the presence of Li+ which inhibits their dephosphorylatron, rt can be concluded that the hydrolysis of phosphatidylmosrtol4,5-biphosphate, and possibly of phosphatidylinosrtol 4-phosphate by phospholipase C 1s markedly accelerated by TRH. It appears that this reaction initiates the acceleratron of phosphatrdylinositol turnover. The specificity of hormonally regulated phospholipase C reaction for polyphosphoinosmdes has important implications for the potential role of the phospholipid response as a mechanism of membrane signal transduction. LlthrumPhospholrpld response

No abstract

HPLC methodology has found wide application in analytical problems in biochemistry. To study the metabolism of phosphatidylinositol and its regulation by receptor mediated events, HPLC could be a valuable technique. It has been recently demonstrated that a variety of hormones and neurotransmittors act to stimulate hydrolysis of phosphoinositides by a phospholipase C. To monitor this reaction, we have analysed the formation of radiolabelled inositol phosphates from phosphoinositides. The present paper describes a rapid HPLC procedure, to separate inositol phosphates from myo-inositol, which could be used in pharmacological studies of receptors linked to phosphoinositide hydrolysis. The potential of the application of HPLC to the analysis of the phospholipids involved is discussed.