Studies on catabolism of 125I-labelled fibrinogen in normal rabbits and in rabbits with indwelling intravenous catheters: methodologic aspects.

The catabolism of rabbit fibrinogen labelled with radioactive iodine was studied over a period of 7-9 days in normal rabbits and in rabbits with indwelling intravenous catheters. The labelled fibrinogen was highly clottable and homogeneous on immunoelectrophoresis and disc electrophoresis. The protein-bound 125I-activity amounted to at least 99%. Normal rabbits with a weight between 1.6 and 2.2 kg exhibited a mean plasma volume of 41.65 ml/kg. A mean half-life time of 1.69 days and a mean fractional catabolic rate of 59.8% of the plasma fibrinogen pool per day was computed by tracing labelled fibrinogen. The absolute catabolic rate revealed a mean value of 58.7 mg/kg body weight/day. Comparable results were obtained for all three labelled fibrinogen batches. A siliconized polyvinyl tubing with an outer diameter of 2.0 mm inserted into a jugular vein up to a length of 10-12 cm and indwelling for more than 10 days did not significantly influence the parameters studied for controlling the fibrinogen catabolism except for the absolute catabolic rate of 112.8 mg/kg/day which differed significantly from that of the control group. Thus, the indwelling intravenous catheter had no or only a minor effect on the activation of intravascular coagulation.