Some properties of the reticuloendothelial-depressing substance of the dog

Abstract

The intact rat was used to determine the presence of reticuloendothelial-depressing substance (RDS) in terms of the percent decrease from the normal rate of carbon particle clearance from the blood stream. The RDS content of whole plasma could not be determined in the rat. However, dialysates, protein-free filtrates, and methylene chloride extracts of plasma from shocked animals showed significant amounts of RDS. Methylene chloride and petroleum ether extracts of protein-free filtrates were chromotographed and separated with either of 2 solvents. It was found that an area which colored lemon yellow with sulfanilic reagent could be eluted with methanol and would depress the granulopectic activity of the rat. Protein-free filtrates could be stored for at least 1 month at [long dash]30 C at acid pH. However, before extraction with methylene chloride it was necessary to make the pH alkaline. The nature of RDS is unknown, but it is suggested that it is a small molecule which does not act on the reticuloendothelial system by "blockade.".