The absorption of phospholipid vesicles by perfused rat liver depends on vesicle surface charge

Two types of sonicated vesicle have been prepared from dipalmitoylphosphatidylcholine (DPPC) by incorporation of phosphatidylinositol (PI) to give negatively charged vesicles and stearylamine to give positively charged vesicles. The absorption of the vesicles by rat liver has been investigated by perfusion techniques. A steady state of vesicle absorption is rapidly established in approx. 2 min and the initial rates of absorption decrease with PI content of the vesicles and increase with stearylamine content. In the steady state, the uptake of vesicles by the liver is similarly dependent on vesicle charge, being inhibited by PI and enhanced by incorporation of stearylamine in the vesicles. Fractionation of the liver into subcellular fractions following perfusion showed that most of the vesicular lipid could be found associated with a nuclear (plus plasma membrane) fraction. The suppression of vesicle absorption by PI may be of value as a means of bypassing the liver in relation to the use of vesicles as a delivery system.