Effect of hypocholesterolemic agents on central nervous system cholesterol biosynthesis III. Zuclomiphene in combination with AY9944 and triparanol

Studies on the mechanism of the epileptiform activity induced by U18666A. II. Concentration, half-life and distribution of radiolabeled U18666A in the brain

The concentration, half-life, and distribution in brain of U18666A, a drug that can drastically alter cerebral lipids and induce a chronic epileptiform state, was determined following both acute and chronic drug administration. U18666A specifically labeled with tritium was prepared by custom synthesis. Brain levels of 1 x 10(-6)M and higher were reached soon after giving an acute 10-mg/kg dose (i.p. or s.c.) of U18666A containing 7-3H-U18666A of known specific activity. A steady state concentration of 1 to 2 x 10(-6)M was reached with chronic injection of 10 mg/kg every 4th day, a treatment schedule that results in altered brain lipids and induction of epilepsy if begun soon after birth. The disappearance of U18666A from both brain and serum was described by two similar biexponential processes, a brief rapid clearance (t1/2 = 10 h) and a sustained and much slower one (t1/2 = 65 h). Brain levels of the drug were about 10 times higher than serum at all times examined. Few differences were seen in the regional distribution of radiolabeled drug in brain as determined by both direct analysis and by autoradiographic examination; but the drug did concentrate in lipid-rich subcellular fractions. For example, the synaptosome and myelin fractions each contained about 25-35% of both the total 3H-labeled drug and total lipid in whole brain. The lipid composition of these fractions was drastically altered in treated animals. In conclusion, the chronic epileptiform state induced by U18666A does not appear to involve localization of the drug in a specific brain region or particular cell type. Rather, the condition could involve localization of the drug in lipid-rich membranes and marked changes in the composition of these membranes.

The biochemical and morphological response of hydrolytic enzymes in the developing brain to hypocholesterolemic agents

Administration of hypocholesterolemic agents to developing rats has been found to selectively induce brain hydrolases. Certain regimes also caused an appreciable increase in total brain protein content. The hypocholesterolemic agents AY-9944 and zuclomiphene were tested individually and in combination. A fourth type of treatment utilized the above drugs in combination with Triparanol. Whenever AY-9944 was used, singly or in combination with other compounds, the beta-glucuronidase activity of developing brain was increased. Acid phosphatase and total brain protein were increased in animals treated with AY-9944 plus zuclomiphene or AY-9944 plus zuclomiphene and Triparanol. Neither AY-9944 nor zuclomiphene alone significantly affected brain total protein or acid phosphatase. Electron microscopic examination of tissue specifically reacted for acid phsophatase demonstrated that the increased enzyme activity was localized in cells in the perivascular spaces. Alkaline phosphatase and N-acetyl-beta-glucosaminidase, two other hydrolytic enzymes assayed, seemed to be much less influenced by the drug treatments.