STUDIES ON THE MECHANISM OF ACTION OF RILEY VIRUS IV. Tm~ R.ETICULOENDOTHELIAL SYSTEM AND IMI~AIRED PLASMA ENZYME CLEARANCE IN INFECTED MICE

In mice infected with Riley virus (1), the activities of a number of plasma enzymes are permanently elevated (2, 3). Similar, although temporary, increases in plasma enzyme activity have been produced in mice by the administration of certain substances which reduce the phagocytic activity of the reticuloendothelial system (RES), and so it was suggested that in both cases the increased plasma enzyme levels might be caused by inhibition of plasma enzyme clearance by the RES (4). Previous studies in Riley virus-infected mice have demonstrated a reduced rate of plasma clearance for those enzymes which have an increased activity in the plasma of infected mice. The enzymes for which this relationship has been demonstrated are lactate dehydrogenase (LDH), isocitrate dehydrogenase, malate dehydrogenase, and aspartate transaminase (formerly called glutamic-oxalacetic transaminase) (5-7). With two other enzymes, alkaline phosphatase and the LDH-1 isoenzyme of LDH, the rate of clearance from the plasma was the same in normal and Riley virus-infected mice, and the plasma activities of these enzymes remain unchanged after Riley virus infection (6, 8). The present study was undertaken to extend previous work on plasma enzyme clearance in Riley virus-infected mice, and to examine the effect of altered RES activity on plasma LDH clearance in noninfected mice.