Flow cytometric method using fluorescent microspheres to measure reticuloendothelial function or particulate translocation

The reticuloendothelial system (RES) influences the outcome of vascular sho ck and environmental stress. We describe a procedure that employs now cytom etry and 1 mu m fluorescent microspheres (FM) to study RES function. FM (2 x 10(10) beads/kg) were administered via a jugular cannula in Sprague-Dawle y rats. After 15 min, blood and tissues were collected and digested in 15% KOH, Phycoerythrin 1 mu m beads were added to each sample as an internal st andard and analyzed by now cytometry, FM were preferentially cleared by the spleen, liver and lung. Clearance was confirmed by fluorescent photomicros copy. Addition of the internal standard to determine accurately aspiration volume enhanced precision. This procedure offers advantages over other RES clearance methods including bacterial, radioactive or carbon clearance assa ys. Moreover, this method could enhance accuracy, reproducibility and speed of data collection in particulate transport studies that are based on manu al microscopy scanning and FM counting.