A NEW LOOK AT RETICULOENDOTHELIAL BLOCKADE

Abstract

The characteristics of so-called RES blockade were reinvestigated in mice using organ uptake, rather than blood clearance, as the main assessment method. Blockade was induced by using i.v. dextran sulfate. I.v. 51Cr-labeled sheep red blood cells were used as test particles. Although colloid clearance from the bloodstream induced prolongation of RES clearance of a subsequent test particle dose, this was solely due to hepatic phagocytosis depression and the splenic and bone-marrow clearance remained unimpaired. Because of this highly selective action of i.v. blockading colloid, and because testing via the i.v. route can only provide information about macrophages which line blood channels, the expression RES blockade is entirely inappropriate to describe these phenomena. The effects could be quantitated using a wide range of doses of this test particle and saturating doses were not required.