Noradrenaline stimulation of the phosphoinositide system: evidence for a novel hydrophobic inositol‐containing compound in resistance arterioles

Abstract

Five inositol phosphates were extracted from adult rat resistance arterioles and separated by ion‐exchange high performance liquid chromatography. By use of this technique, inositol phosphates liberated were identified as inositol 1‐phosphate, inositol 1,4‐bisphosphate, inositol 1,3,4‐trisphosphate, inositol 1,4,5‐trisphosphate and inositol 1,3,4,5‐tetrakisphosphate. Stimulation of phosphoinositide hydrolysis with noradrenaline produced increases in inositol phosphate production. Three inositol‐containing phospholipids extracted from resistance arterioles were measured as their glycerol esters following deacylation, thereby permitting an analysis of both membrane and cytosolic components of the phosphoinositide signalling system. A substantial agonist‐sensitive pool of a previously undescribed inositol but not glycerol‐containing lipid extract component was also identified in this tissue. These experiments for the first time allow a precise description of phosphoinositide metabolism in resting and agonist‐stimulated resistance arterioles and provide data on a novel compound possibly similar to that recently described in other tissues. 1988 British Pharmacological Society