Summary
This investigation determined the organ distribution of liposomes containing egg phosphatidylcholine
and cholesterol with egg phosphatidylglycerol (PG liposomes) or without (PC liposomes)
and the effect of each liposome on platelet distribution in rabbits. Eight minutes
after51 chromium-labelled platelets were given intravenously, either saline (n = 7), iodinated
PG liposomes (n = 5) or iodinated PC liposomes (n = 5) were infused. T\ro minutes
later the organ distribution of 51Cr-platelets and 125I-liposomes were compared. The PG liposomes produced a 41λ5% reduction in circulating
platelet counts while PC liposomes did not. The PG liposomes decreased circulating
51Cr-platelets by a factor of 2 and increased platelet recoveries in the liver and lungs.
The increased platelet recovery in the liver was associated with a greater PG liposome
recovery. When animals receiving PG liposomes were studied over 60 minutes, both the
labelled and unlabelled platelet counts returned to control values by 30 minutes and
the 51Cr-platelet distribution between organs was similar to control values. These data
indicate that platelets and PG liposomes initially sequester together and that this
plateletliposome interaction is specific for PG liposomes. However, the platelet sequestration
is transient and by 60 minutes the platelets were released and circulating.
Keywords
Platelets - Liposomes - Platelet-endothelial interactions - Liposome biodistribution
- Radiolabelled platelet kinetics - Platelet-liposome interactions