Effect of chlorpromazine and azacyclonol on the labelling of phosphatides in brain slices

Effect of chlorpromazine on lipid metabolism in aortas from cholesterol-fed rabbits and normal rats, in vitro: inhibition of sterol esterification and modification of phospholipid synthesis

Chlorpromazine (CPZ), a major tranquilizer, was found to be a potent inhibitor of acylCoA:cholesterol acyltransferase (ACAT, EC 2.3.1.26) in isolated arterial microsomes and in intact arterial tissue from the rat and cholesterol-fed rabbit in vitro. In isolated rabbit arterial microsomes, CPZ resulted in a concentration-dependent inhibition of ACAT with 50% inhibition of [1-14C]oleoylCoA incorporation into [14C]cholesteryl esters occurring at 0.1 mM CPZ. CPZ also effectively inhibited the incorporation of [14C]oleate into triglycerides without affecting incorporation into diglycerides. Additionally, CPZ altered the pattern of arterial phospholipids synthesized from [1-14C]oleate. Incorporation into phosphatidylcholine was depressed while incorporation into phosphatidylinositol was increased. Since diglyceride synthesis appeared to be unaffected by CPZ, a redirection of phosphatidic acid into the CDP-diglyceride pathway of glycerolipid synthesis does not adequately account for the effect of CPZ on arterial phospholipid and triglyceride synthesis in these experiments.

INCORPORATION OF INORGANIC P32INTO PHOSPHOLIPIDS OF BRAIN SLICES: EFFECT OF CERTAIN TRANQUILLIZING DRUGS

Promazine, promethazine, tetrameprazine, and WY 1172, four tranquillizing drugs that are derivatives of phenothiazine, resembled chlorpromazine in that when they were added in a concentration of 0.1 mM to slices of guinea pig brain respiring in a suitable medium they stimulated the incorporation of inorganic P32into the phospholipids of the slices. With one of the drugs, promethazine, this concentration of 0.1 mM was found to cause no significant increase in respiration, in aerobic glycolysis, or in the concentration of phosphocreatine. In higher concentrations (1.0 mM), all of the compounds inhibited the labelling of phospholipid. Promethazine caused a reduction in respiration and in the concentration of phosphocreatine, accompanied by an increase in aerobic glycolysis. Methylene blue, a derivative of phenothiazine with no reported tranquillizing properties, did not stimulate the labelling of phospholipid in brain slices. Azacyclonol, pipradrol, and mepazine, drugs that are derivatives of piperidine, also stimulated phospholipid labelling in low concentrations and inhibited the labelling at higher concentrations. Piperidine and benzhydrol, the two components from which azacyclonol is derived, did not stimulate phospholipid labelling at the concentration which was most effective for azacyclonol. Low concentrations of benzhydrol, however, caused a slight stimulation. Meprobamate and phenaglycodol, two other compounds with reputed tranquillizing action, had either little or no effect. Most of the substances tested inhibited phospholipid labelling when they were added in sufficiently high concentrations.

FORMATION OF PHOSPHATIDES FROM C14-LABELLED PRECURSORS IN RAT BRAIN SLICES. EFFECT OF CHLORPROMAZINE

The addition of chlorpromazine (0.1 mM) to slices of rat brain respiring in a suitable medium caused an increase in the incorporation of radioactivity from glycerol-1-C14, glycine-2-C14, and serine-3-C14 into the phospholipids of the slices. There was no increase in the incorporation of radioactivity from choline-1,2-C14 or ethanolamine-1,2-C14. Examination of the individual phosphatides showed an increase in the incorporation of radioactivity from glycerol-1-C14 into phosphatidc acid and phosphatidyl serine, with no change for lecithin and phosphatidyl ethanolamine. Higher concentrations of chlorpromazine (1.0 mM) either inhibited (glycerol-1-C14, choline-1,2-C14), did not significantly alter (glycine-2-C14, ethanolamine-1,2-C14), or stimulated (serine-3-C14) the incorporation of radioactivity into phospholipids. These results are discussed in relation to previous experiments, in which it was found that the addition of chlorpromazine (0.1 mM) to slices of guinea pig brain caused an increase in the incorporation of inorganic P32 into phosphatidic acid, phosphatidyl inositol, phosphatidyl serine, but not into lecithin or phosphatidyl ethanolamine.

INCORPORATION OF INORGANIC P32INTO PHOSPHOLIPIDS OF BRAIN SLICES: EFFECT OF CERTAIN TRANQUILLIZING DRUGS

Promazine, promethazine, tetrameprazine, and WY 1172, four tranquillizing drugs that are derivatives of phenothiazine, resembled chlorpromazine in that when they were added in a concentration of 0.1 mM to slices of guinea pig brain respiring in a suitable medium they stimulated the incorporation of inorganic P32into the phospholipids of the slices. With one of the drugs, promethazine, this concentration of 0.1 mM was found to cause no significant increase in respiration, in aerobic glycolysis, or in the concentration of phosphocreatine. In higher concentrations (1.0 mM), all of the compounds inhibited the labelling of phospholipid. Promethazine caused a reduction in respiration and in the concentration of phosphocreatine, accompanied by an increase in aerobic glycolysis. Methylene blue, a derivative of phenothiazine with no reported tranquillizing properties, did not stimulate the labelling of phospholipid in brain slices. Azacyclonol, pipradrol, and mepazine, drugs that are derivatives of piperidine, also stimulated phospholipid labelling in low concentrations and inhibited the labelling at higher concentrations. Piperidine and benzhydrol, the two components from which azacyclonol is derived, did not stimulate phospholipid labelling at the concentration which was most effective for azacyclonol. Low concentrations of benzhydrol, however, caused a slight stimulation. Meprobamate and phenaglycodol, two other compounds with reputed tranquillizing action, had either little or no effect. Most of the substances tested inhibited phospholipid labelling when they were added in sufficiently high concentrations.

FORMATION OF PHOSPHATIDES FROM C14-LABELLED PRECURSORS IN RAT BRAIN SLICES. EFFECT OF CHLORPROMAZINE

The addition of chlorpromazine (0.1 mM) to slices of rat brain respiring in a suitable medium caused an increase in the incorporation of radioactivity from glycerol-1-C14, glycine-2-C14, and serine-3-C14 into the phospholipids of the slices. There was no increase in the incorporation of radioactivity from choline-1,2-C14 or ethanolamine-1,2-C14. Examination of the individual phosphatides showed an increase in the incorporation of radioactivity from glycerol-1-C14 into phosphatidc acid and phosphatidyl serine, with no change for lecithin and phosphatidyl ethanolamine. Higher concentrations of chlorpromazine (1.0 mM) either inhibited (glycerol-1-C14, choline-1,2-C14), did not significantly alter (glycine-2-C14, ethanolamine-1,2-C14), or stimulated (serine-3-C14) the incorporation of radioactivity into phospholipids. These results are discussed in relation to previous experiments, in which it was found that the addition of chlorpromazine (0.1 mM) to slices of guinea pig brain caused an increase in the incorporation of inorganic P32 into phosphatidic acid, phosphatidyl inositol, phosphatidyl serine, but not into lecithin or phosphatidyl ethanolamine.