1. The presence of a phosphatidylinositol kinase in homogenates of adult rat brain was shown by using labelled ATP or labelled phosphatidylinositol. 2. The kinase was activated by Mg(2+) or Mn(2+) and inhibited by Ca(2+), Cu(2+), K(+), Na(+) and F(-). 3. The detergents sodium deoxycholate, Cutscum and Triton X-100 markedly stimulated the reaction; sodium taurocholate, Tween-20 and cetyltrimethyl-ammonium bromide were less effective. 4. The activity of the enzyme was dependent on SH groups. 5. The subcellular distribution of the kinase in brain resembled that of Na(+)-plus-K(+)-stimulated adenosine triphosphatase and 5'-nucleotidase.
Abstract— Paired vagus nerves, phrenic nerves or superior cervical ganglia from rats were incubated at 37 C for various times in a simple salt solution containing glucose and 32Pi. One of the pair was usually stimulated electrically for 30 or 60 min. Stimulation of vagus nerve for 30 min increased phosphate incorporation into all the phospholipids studied but the increase was significant only in the case of triphos‐phoinositide and diphosphoinositide. This increase was not accompanied by increased labelling of the nucleotide labile phosphate pool. Tetrodotoxin at concentrations sufficient to block transmission had no effect upon phospholipid labelling in vagus or phrenic nerve. Ouabain at blocking concentration did not affect polyphosphoinositide metabolism in vagus nerve but increased [32P]labelling of the other phospholipids. Hemicholinium‐3 increased the labelling of all three phosphoinositides in the sympathetic ganglia but the increase in phosphatidylinositol labelling due to electrical stimulation was not seen in the presence of this inhibitor.
Abstract— Paired vagus nerves, phrenic nerves or superior cervical sympathetic ganglia from adult white rats were incubated for 4 h at 37°C in a bicarbonate‐buffered physiological solution containing glucose and 32P1. At the end of incubation triphosphoinositide (TPI) contained more 32P than any other lipid in the vagus nerves and was second only to phosphatidylcholine (PC) in the phrenic nerves. In the sympathetic ganglia phosphatidylinositol (PI) contained more 32P than did TPI, but both had less than PC. Conducted nerve impulses, initiated by electrical stimulation during the final 3 h of incubation, caused a highly significant increase in the [32P]‐labelling of PI in ganglia (as previously reported) probably decreased the labelling of TPI in the vagus nerves, and decreased the labelling of phosphatidylethanolamine (PE) in the ganglia. Addition to the incubation medium of §‐ or γ‐hexachlorocyclohexane (analogs of inositol) reversibly blocked transmission through the sympathetic ganglia at concentrations less than 0·1 mM. The §‐isomer also blocked conduction along axons at similar concentrations; only the γ‐isomer (lindane) exerted a selective effect on synaptic transmission. In the ganglia, the §‐isomer increased the [32P]‐labelling of PI and diphosphoinositide (DPI) relative to that of PC. The γ‐isomer did not affect the relative labelling of PI in the ganglia, whereas it decreased that of TPI, but only at relatively high concentrations. Thus, various affects of the hexachlorocyclohexanes were not explicable by assuming that they acted as analog inhibitors of inositol metabolism. In the ganglia, the hexachlorocyclohexanes reduced the effect of neuronal activity on the labelling of PI in proportion to the extent by which they blocked transmission. This metabolic effect was therefore presumed to be secondary to a ganglionic blocking action.
The phospholipid composition of Schizosaccharomyces pombe was not markedly affected by changes in the phosphate concentration of the medium or phase of growth. The major fatty acids in the total lipid extract and purified phosphatidylinositol were palmitic acid and oleic acid. Phosphatidic acid was synthesized by acylation of l-3-glycerophosphate in Schiz. pombe and phosphatidate phosphohydrolase was present. Phosphatidylinositol synthesis from inositol occurred in the absence of CDP-diglyceride. Even with dialysed cell-free preparations, the inositol lipid was synthesized by an apparently energy-independent route, at rates greater than would be required during cell growth. Phosphatidylinositol appeared to be broken down by a phospholipase D. All the enzymes examined were particulate; similar activities were found in Saccharomyces cerevisiae.
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