Elimination of bovine haptoglobin from rat circulation.

The rate of elimination from rat circulation of bovine or rat haptoglobin, of their complexes with homologous haemoglobin, and of preparations deprived of the terminal sialic acid (asialo-haptoglobin), was studied. The rate of elimination was identical for bovine haptoglobin and its complexes with bovine or rat haemoglobin (the half-life time, t1/2, was 10 h). The half-life time of complexes of rat haptoglobin with bovine or rat haemoglobin was about 2 h, and it was much shorter than t1/2 for rat haptoglobin (13 h). The shortest half-life time was observed for bovine and rat asialo-haptoglobin, 35 and 15 min, respectively. The elimination curves showed a biphasic or triphasic character, depending on the rate of elimination.