Magnetometric Measurements of Macrophage Activity in the Liver after Administration of Different Perfluorochemicals

Abstract

Ferromagnetic particles, phagocytosed by macrophages of the liver, can be sensed magnetometrically after application of a strong external magnetic field. ^1–5 Immediately after the end of magnetization, a loss of alignment of the phagocytosed particles begins, called magnetic relaxation,^6,7 which can be measured by means of a sensitive magnetic probe. The velocity of this disalignment depends on phagosomal motion within the cells and thus is an indirect measure of phagocytic activity.^7–10 Artificial oxygen carriers like perfluorochemicals are taken up by the same cell type within the reticulo-endothelial system (RES).^11–14 However, large differences seem to exist between several generations of these blood substitutes and diagnostic agents. The first generation, represented by Fluosol^R-DA (FSD),^15–17 offered the disadvantage of needing a frozen state to be conserved, a low concentration of the effective emulsion and a prolonged retention within tissues. These handicaps seem widely overcome by second generation fluorochemical emulsions based on perfluoroctylbromide (PFOB,^18,19 perflubron, Oxygent^TM HT). The above mentioned method was therefore applied to test differences between both types of oxygen carriers concerning their effects on cells of the RES. Since the measurements are non-invasive, longitudinal studies in the same animals of a group can be undertaken after different time periods following administration of the substances