Myocardial phosphoinositides do not share the same fatty acid profile.

Overview

It is generally assumed that the fatty acid compositions of the phosphoinositides are identical. To investigate this in myocardium, inositol lipids extracted from rat and pig ventricular homogenates were absorbed to neomycin-coated glass beads, eluted and quantitated by fatty acid analysis after thin-layer chromatography. The percentages of stearic, oleic, linoleic and arachidonic acid (20:4n-6) in the rat were, respectively, 49, 4, 7 and 26 for phosphatidylinositol, 62, 1, 4 and 18 for phosphatidylinositol-4-monophosphate and 63, 2, 4, 18 for phosphatidylinositol-4,5-bisphosphate. Equal distribution patterns of fatty acids were found in homogenate and sarcoplasmic reticulum of pig myocardium. Cultured rat ventricular myocytes were utilized to study the incorporation (25 h) of [14C]20:4n-6 relative to that of myo-[3H]inositol into phosphatidylinositol and phosphatidylinositol-4,5-bisphosphate which were, respectively, 1.61 and 1.22. The data indicate that in myocardium phosphatidylinositol-4,5-bisphosphate represents a relatively modest source of 20:4n-6.