INTRAVASCULAR BEHAVIOR OF PERFLUBRON EMULSIONS

Perflubron emulsion particles are removed from the circulation of test animals by the organs of the reticuloendothelial system (RES). Initia l removal is rapid and results in a loading of the RES. Subsequent rem oval is first order in perflubron concentration, but the rate constant is inversely related to perflubron dose. At longer times, the perflub ron which initially went to the RES is solubilized in blood lipids. Fo r particles stabilized with egg yolk phospholipid (EYP), the first-ord er perfluorocarbon elimination rate constant is directly proportional to particle size and is not dependent on the identity of the emulsifie d perfluorocarbon. The rate constant can be changed by addition of sur face modifiers to the EYP. In rats, most changes speed elimination. In rabbits, the rate constants are much smaller than in rats, but the si ze dependence is still present. Changing the particle surface also aff ects the elimination rates in rabbits. The results of surface changes are highly species dependent, and the intravascular behavior of perflu bron emulsions in rabbits is very different from that in rats, dogs an d swine.