Measurement of the clearance function of macrophages with 125i- -labelled polyvinyl pyrrolidone.
The rate constant of the exponential decay in blood radioactivity between 18 and 48 hr after intravenous injection of 30–80 μg of 125I-labelled polyvinyl pyrrolidone (PVP) in mice has the characteristics of a test of the clearance function of macrophages. It is reduced by carbon, PVP or hydrocortisone, and increased by oestrogen. Clearance is independent of dose over this range, and probably measures resting unstimulated phagocytic function; this is perhaps different from the function measured by existing techniques. Preliminary evidence suggests that it is applicable to man.