Plasma clearance of I125 des-AA fibrin mcncmers was studied in healthy subjects (N=7). Labelled mcnaners (fm),
made fran labelled fibrinogen (F) in 2,5 M urea, pH 7,4 exposed to insoluble reptilase
(Brosstad et al., Thrarto .Res. 13, 1978) vere solubilized upon addition to test-subject
plasma, and subsequently injected. At intervals, citrated plasma samples ware tested
for: I. Total radioactivity (Tr). II. Radioprecipitability (Rp) with trichloroacetic
acid. III. Radioclottability (Rc) with plasmin-free thrcmbin (pH 6,3 1h). IV. Radiodistribution
after ultrasentrifuga-ticn (Airfug, Beckmann) and V. Radiodistributicn in SDS-PAGE
gels after electrophoresis of harvested EDTA-plasma clots, solubilized in urea-SDS.
RESULTS: Prior to injection, plasma demonstrated: Rp = 100 %, Rc = 94 %, single peak
ultracentrifuge pattern and 95 % of total radioactivity moving as F on SDS-gels. Almost
identical results were obtained in all subjects. After 30 min., Tr had dropped to
50 % of Tr value at 5 min., being 10 % and 2 % after 420 min. and 48 h., correspondingly.
A parallell drop in Rp and Rc scarcely noticeable at 10 min., reached a mininun of
30 % at 360 min; the Airfug and SDS-gel patterns substantiating these findings. Due
to non-linearity on semilog. plots, a definite half-life of des-AA fibrin cannot be
stated from decay parameters (Tr) alone, but metabolic data as outlined above (Rp,
Rc, Airfug, SDS-elpho) suggest a half-life of 30-60 min .. In five subjects, I131-des-AA fibrin and I125-fibrinogen was injected simultaneously. Clearance rates characteristic of that of
the individual molecular species were obtained. The extremely rapid elimination of
fibrin ccnpared to that of fibrinogen suggests specific receptors on RES- cells to
be involved.
