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.