Morphological observations on the fate of liposomes in the regional lymph nodes after footpad injection into rats.
Multilamellar liposomes composed of equimolar egg phosphatidylcholine and cholesterol and containing carboxyfluorescein or colloidal gold were injected subcutaneously into the footpad of the hind-leg of rats. The draining popliteal lymph nodes of animals killed at time intervals after injection were then dissected and sections examined by fluorescence microscopy (carboxyfluorescein), light microscopy using an immunogold silver kit to enhance gold particles or by transmission electron microscopy. Morphological observations confirmed that subcutaneously injected liposomes accumulate in large numbers in the draining lymph node. The majority of liposomes arrived at the subcapsular sinuses, probably via afferent lymphatic vessels, as such, i.e., in a non-cell bound form. Subsequently, liposomes were dispersed throughout the lymph node either by permeation as free vesicles along the sinuses or by cells involved in vesicle uptake. The majority of such cells were free macrophages, littoral cells and reticular cells (fixed macrophages). Once within cells, liposomes were seen digested by the lysosomal apparatus with varying loss of their lamellar structure, leaving free gold particles within the lysosomes.
Velinova
M
M
Centre for Drug Delivery Research, School of Pharmacy, University of London, UK.
Read
N
N
Kirby
C
C
Gregoriadis
G
G
D000818:Animals; D006046:Gold / Q000032:analysis; D006614:Hindlimb; D007150:Immunohistochemistry; D007279:Injections, Subcutaneous; D008081:Liposomes / Q000008:administration & dosage / Q000493:pharmacokinetics*; D008198:Lymph Nodes / Q000378:metabolism* / Q000648:ultrastructure; D008247:Lysosomes / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D051381:Rats; D017208:Rats, Wistar
D008081:Liposomes; D006046:Gold