Studies on the Mechanism of Action of Ru,ey Virus I. Action of Substances Az]~ecting Tiie Reticuloeni)ot]ielial System on Plas~.a Enzyme Levels in Mice

It was recently suggested that the increases in plasma enzyme activity following infection of mice with Riley virus (1) might be due to inhibition of the clearance of enzymes from the blood plasma (2). Preliminary studies confirmed that the plasma clearance of intravenously injected lactate dehydrogenase (LDH) was greatly impaired in Riley virus-infected mice, and also showed that blood clearance of colloidal carbon, a measure of reticuloendothelial activity, was temporarily depressed concurrently with the peak plasma virus titre (3, 4). There is some evidence that enzymes are removed from the plasma by the reticuloendothelial system (RES) (5). We have therefore studied the effects of various agents known to stimulate or depress RES function on plasma enzyme levels in normal or Riley virus-infected mice. A preliminary report of this work has been published (6).