Uptake and tissue distribution of liposomes after intraperitoneal administration to rainbow trout, Oncorhynchus mykiss (Richardson): a preliminary report

Liposomes were prepared from phosphotidylcholine and cholesterol at a molar ratio of 4:1. One group of 10 fish received an intraperitoneal injection of multilamella liposomes (MLV), while another group received large unilamellar liposomes (LUV). Approx. 20 micro Ci of tritiated cholesterol had been incorporated per 50 micro moles of lipid, and radioactive counts from each liposome preparation averaged 280 000 cpm/10 micro l of the liposome suspension before injection. The fish were killed 24 h after injection and the various tissues examined for radioactivity. Uptake of LUVs was significantly greater than that of MLVs. The spleen, and anterior and posterior kidney were primary sites of localization. Liver had the next greatest uptake, followed by gills, heart and fat; muscle tissue had the lowest uptake. It is suggested that LUVs would provide an appropriate delivery system for vaccines, as well as for certain antimicrobial agents..