Incorporation of polyenephosphatidylcholine into serum lipoproteins after oral or intravenous administration.

Radioactive polyenephosphatidycholine (PPC) was injected i.v. in dogs, rats and rabbits. In addition, PPC was administered orally to dogs and rats. The incorporation of the PPC applied into serum lipoproteins was determined. After i.v. injection in dogs approximately 80% of the radioactive dose was transported by HDL. Only around 50% of the dose was found, however, in the HDL fraction of rats and rabbits. Radiochemical analyses provided a quantitative determination of the time course of PPC incorporation into HDL as well as of the metabolites of PPC. After in vitro incubation with rat and human serum PPC was incorporated into HDL by approximately 50% of the applied dose and by 5--14% into LDL, by approximately 15% into VLDL and by 20--30% into other serum constituents. In vitro incubation of PPC with human HDL yielded the complete incorporation into this lipoprotein fraction.

Effect of polyenephosphatidylcholine on cholesterol uptake by human high density lipoprotein.

The lipid and protein composition of human HDL was changed by incorporation of polyenephosphatidylcholine (PPC) into HDL in vitro. HDL with incorporated PPC (HDL-PPC) had a higher molar PC/apoprotein ratio than native HDL. PPC accounted for up to 50% of the PC fraction of HDL. The fluidity of HDL-PPC was higher than that of native HDL but lower than that of PPC liposomes. Zonal ultracentrifugation separated HDL-PPC into a major and a minor component. The AI/AII ratio of the major fraction was reduced compared with native HDL. The storage capacity of HDL-PPC and native HDL for cholesterol was studied by incubation of these fractions with [14]cholesterol-LDL. Significantly more cholesterol (55%) was taken up by HDL-PPC from LDL than by native HDL. The transfer of cholesterol from LDL to HDL in human serum was studied by an in vitro [14C]cholesterol distribution test. In this test the lipoproteins of serum were labelled with [14C]cholesterol. An analytical procedure was developed to quantify the transfer of cholesterol from LDL to HDL after addition of PC. The transfer depended on the fluidity and the dose of the PC fraction used as well as on the initial LDL + VLDL/HDL ratio and was independent of LCAT activity.

[Approval of drugs by national and European agencies--sequelae for the pharmaceutical industry]. / Zulassung von Arzneimitteln durch nationale und europäische Behörden--Konsequenzen für die pharmazeutische Industrie.

The research-based pharmaceutical industry supports the European harmonization process for the granting of pharmaceutical registrations. In order to improve consumer protection and the therapeutic options available to physicians in comparison to nationally registered products, the harmonization must be carried out on schedule and transparently a high scientific standard. It must not lead to the adoption of all national restrictions regarding data sheets and patient leaflets. Pharmaceutical products with the same ingredients can be registered either through the national or through the European procedure. This situation can only be remedied by the harmonization of core SPCs. This process must be agreed in consultation between pharmaceutical companies and regulatory authorities. With regard to measures to avert drug risks, professional associations and the pharmaceutical companies affected should be heard by the national authorities and their arguments given due consideration. In addition, national authorities and the CPMP must coordinate their decisions before they are published. In particular, the basis of these decisions should be made clear and therapeutic alternatives should be known.

Pharmacokinetics and metabolism of i.m. injected polyenylphosphatidylcholine liposomes.

The pharmacokinetics of i.m. applied polyenylphosphatidylcholine liposomes has been investigated in rats with the aid of 3H- and 14C-labelled di-linoleoyl-sn-glycerophosphocholine. The experiments stated an efflux of polyenylphosphatidylcholine from muscle injection site with a half-life of 8.6 h. The analysis of remaining polyenylphosphatidylcholine at muscle injection site showed the great stability of this substance. After 24 h approximately 60% of remaining polyenylphosphatidylcholine are not disintegrated. Polyenylphosphatidylcholine was transported mainly to liver by high-density lipoproteins and other fractions with greater density. The rate constants were calculated. Approximately 50% of applied polyenylphosphatidylcholine were incorporated into liver as intact di-linoleoyl-sn-glycerophosphocholine. Hydrolyzed fatty acids form triglycerides and cholesterolesters whereas lyso-phosphatidylcholine is reesterified to phosphatidylcholine again.

Kinetic study of deuterium-labelled polyenphosphatidylcholine after oral administration to rats.

Deuterium-labelled di-[( 15,15,16,16-2H4]-linoleoyl) -3-sn-glycero-phosphocholine was used as a tracer of the major component of soybean polyene-3-sn-phosphatidylcholine to study the pharmacokinetics of a natural product after oral administration to rats. For this purpose a method was developed to isolate the phosphatidylcholine fraction from blood in a highly purified form. Only 200 pg deuterium-labelled fatty acid generated from the phosphatidylcholine fraction and a ratio of one molecule of deuterium-labelled stearic acid to 500 molecules of stearic acid are necessary for a reproducible measurement by gas chromatography/mass spectrometry. The highest amount of di-[( 15,15,16,16-2H4]-linoleoyl) -3-sn-glycerophosphocholine (0.12% dose/ml, i.e. 2.1% of the maximum absorbed dose) was detected in blood 6 h after administration. The results are comparable with those found after administration of di-[l-14C]-linoleoyl-3-sn-glycerophosphocholine. Hence it is possible to use deuterium-labelled polyenphosphatidylcholine instead of radioactively labelled polyenphosphatidylcholine, especially if a harmless tracer is required.

Amitriptylinoxide: receptor-binding profile compared with other antidepressant drugs.

The interactions of amitriptylinoxide and various antidepressant drugs with different neurotransmitter and drug receptors were investigated by receptor binding studies. Amitriptylinoxide had less affinity than amitriptyline for most of the receptors studied. Half maximal inhibition of acetylcholine receptor binding occurred for amitriptylinoxide at 18 mumol/l (amitriptyline: 0.32 mumol/l). Comparing all studied antidepressants for muscarinic acetylcholine receptor binding, amitriptylinoxide had the weakest affinity of all tested tricyclic compounds. Also the affinity of amitriptylinoxide for alpha-receptor binding was about 60 fold less than that of amitriptyline. For all antidepressants investigated, the lowest affinities were found for benzodiazepine, opiate and beta-receptor binding. The weak affinities of amitriptylinoxide for various receptors may be responsible for its reduced side-effects, while it still retains potent antidepressant properties by stabilising the amitriptyline-level in the brain.

Intestinal absorption of polyenephosphatidylcholine in man.

The metabolic fate of 1 of 3H/14C-labeled dilinoleoglycerophosphocholine was studied in five patients after oral administration. The 3H label was in choline and 14C was in the two linoleic acid residues. More than 90% of both isotopes was absorbed from the intestine. Seventy to 90% of the 3H radioactivity in blood was linked to phosphatidylcholine (PC) whereas 14C was associated with both PC and nonpolar lipids. At peak activity, the 3H/14C ratio of plasma PC was twice that of oral PC; this suggests that most oral PC was hydrolyzed to lysolecithin before absorption. The mean maximum concentration in total blood volume was 20% of the administered dose for 3H and 28% for 14C. Examination of lipoproteins revealed that the specific activity of PC in high density lipoprotein (HDL) was 2 to 6 times higher than in apoB-containing lipoproteins, and to 2 to 20 times than that of red blood cells or total blood. Thus, absorbed PC seemingly was incorporated preferentially into the HDL fraction of plasma.

13C nuclear magnetic resonance spectroscopic evidence for hydrophobic lipid-protein interactions in human high density lipoproteins.

Phosphatidylcholines, sphingomyelins, cholesterol, and cholesterol esters were enriched with (13)C by chemical synthesis in specific positions of their hydrophilic groups and aliphatic chains. Their spin-lattice relaxation times were determined in organic solvents. The substances were organized as liposomes and recombined with total human high density apolipoproteins and the two separated main components, apolipoprotein A-I (apoLp-Gln-I) and apolipoprotein A-II (apoLp-Gln-II). These (13)C nuclear magnetic resonance data established that in reassembled high density lipoproteins the phospholipid molecules bind to the apoprotein moieties with their hydrophobic fatty acid chains and not with their hydrophilic zwitterionic groups. Apolipoprotein A-I preferentially binds phosphatidylcholine, although its lipid-binding capacity is smaller than that of apolipoprotein A-II. Apolipoprotein A-II avidly reassembles with sphingomyelin by hydrophobic interactions. A model of the molecular organization of the high density lipoportein particle has been derived.