Autoradiographic localization of the acetylcholine-stimulated synthesis of phosphatidylinositol in the superior cervical ganglion.

Abstract

Myo-inositol-2-H3 was incorporated into the lipids in slices of cat superior cervical ganglion. Over 95 per cent of the radioactivity eluted from segments of a chromatogram of the total lipid extract of ganglion slices was recovered as phosphatidylinositol. The remaining radioactivity was recovered as di- and triphosphoinositide. Incubation of ganglion slices with 0.1 m[image] ACh plus 0.1 m[image]. eserlne stimulated the incorporation of myo-inositol-2-H3 into phosphatidylinositol 2 1/2- to 3-fold. There was no stimulation in di- and triphosphoinositide. Tissue autoradiographic studies were carried out using a hlstological method which removes water-soluble compounds but retains lipid-soluble compounds. Grain counts of sections of superior cervical ganglia showed incorporation of myo-inositol-2-H3 throughout the basophilic cytoplasm of the soma and throughout the interneuronal spaces. There was no incorporation in nuclei. The stimulation of myoinositol-2-H3 incorporation was confined to the basophillc cytoplasm of the somata and the periphery of the nuclei. The significance of this stimulation is discussed. It is felt that these data argue against a role of the phosphatidylinositol effect in events confined to the plasma membrane, such as depolarization by acetylcholine or sodium-potassium transport consequent to depolarization. Based on similarities between ganglion cells and the pancreas with respect to both fine structure and the phosphatidylinositol effect, it is suggested that the phosphatidylinositol effect in ganglia may be concerned with intracellular transmembrane transport of proteins, as appears to be the case in pancreas.