Substance P-Stimulated Phosphatidylinositol Breakdown in Guinea Pig Ileum
The breakdown of phosphatidylinositol lipids in cell membranes may have a key role in controlling the rise in cytosolic Ca2+ which occurs on stimulation of a variety of cell-surface receptors. Pre-iously this phenomenon has been studied by monitoring the rate of incorporation or loss of radioactivity from isotopically labelled membrane phospholipids. However, these approaches suffer from the drawback that changes in the levels of the substrates and not the enzymatic products are measured. We have recently found that lithium can be used to inhibit the breakdown of a metabolite of phosphatidylinositol hydrolysis, inositol-1-phosphate, and that the receptor-stimulated accumulation of inositol-1-phosphate after lithium treatment provides a model for the study of drug action . We have now applied this approach to the characterization of substance P receptors on smooth muscle of guinea-pig ileum.
KeywordsEnzymatic Product Longitudinal Muscle Anion Exchange Resin Lithium Treat Accumulation Assay
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