CATABOLISM OF PLASMINOGEN GLYCOFORM-I AND GLYCOFORM-II IN RABBITS - RELATIONSHIP TO PLASMINOGEN SYNTHESIS BY THE RABBIT LIVER IN-VITRO

The metabolisms of the two glycoforms of rabbit plasminogen have been compared in rabbits. Plasminogen I and II (ratio in plasma, 1:2.2) dif fer only in glycan content: plasminogen I probably possesses one N-gly can and one O-glycan, and plasminogen II only one O-glycan. New Zealan d White (NZW) rabbits were injected intravenously with I-125-plasminog en I and I-131-plasminogen II, and blood samples were taken at regular intervals over 5 days. Kinetic behaviors were determined from protein -bound radioactivities using a three-compartment model. Fractional cat abolic rates for plasminogen II in the vascular space (2.42 d(-1)) and the total body (0.56 d(-1)) were significantly greater than those mea sured for plasminogen I (1.12 and 0.45 d(-1)); half-lives were 1.53 an d 1.23 days for plasminogen I and II, respectively (P < .01). Fraction al distributions among the vascular, noncirculating vascular, and extr avascular compartments were 0.41, 0.13, and 0.46 for plasminogen I, an d 0.23, 0.11, and 0.65 for plasminogen II. From these data, we determi ned that plasminogen II was catabolized 4.8 times more rapidly than pl asminogen I and was quantitatively contained largely in the extravascu lar space. By comparison, perfusion of rabbit livers ex corpora sh owe d th at plasminogen II was synthesized and released 5.0 times faster t han plasminogen I over a 5 hour period. The possible roles for these g lycoforms in vivo with respect to their different turnover rates and c ompartmental distributions are discussed. Copyright (C) 1994 by W.B. S aunders Company