Clearance of Desialylated Mouse α-Macroglobulin and Murinoglobulin in the Mouse

Abstract

Mouse α-macroglobulin and murinoglobulin were labeled with ¹²⁵I and utilized for plasma clearance studies performed with mice. Desialylated murinoglobulin was rapidly cleared from the circulation with a half-life of about 5min. On the other hand, desialylated α-macroglobulin showed a biphasic curve: about half was cleared at a rate similar to that of the intact molecule while the remaining half had a shorter half-life of about 20min which was prolonged by a simultaneous injection of a 200-fold excess of unlabeled asialoorosomucoid. Virtually no cross competition was observed between these asialoglobulins and formaldehyde-treated bovine serum albumin or trypsin-bound α-macroglobulin. These results suggest that the intravascular elimination of desialylated α-macroglobulin and murinoglobulin is independent of the clearance systems responsible for formaldehyde-modified proteins or proteinase-bound α-macroglobulins, and that the structure or spatial arrangement, or both, of oligosaccharide units of α-macroglobulin is somewhat different from that of murinoglobulin, resulting in a difference of avidity of interaction with the asialoglycoprotein receptor. The desialylated α-macroglobulin and murinoglobulin accumulated principally in the liver.