Dog IgG was produced by fractionation procedures used for the production of clinically used i.v. gammaglobulins. Chemical modification of dog IgG was done by pepsin or beta-propiolactone treatment. The intravascular half-life of beta-propiolactone IgG was 8.5 +/- 2.1 days compared to 4.5 +/- 1.6 days of pepsin treated IgG. Tissue concentrations of radioactive labelled beta-propiolactone IgG were generally higher than of pepsin digested IgG. Pepsin treated Igg was degraded to a significantly higher extent (26% of the administered radioactivity was bound to fragments smaller than 6000 MW after three days) than beta-propiolactone IgG (9% fragments after the same interval, P less than 0.001). It is concluded that the short intravascular half-life of pepsin IgG cannot be explained by increased extravascular filling, but is due to rapid degradation and excretion via the kidneys. There was no obvious difference in elimination and organ distribution between standard and beta-propiolactone IgG.

Chemical modification of standard gammaglobulin with enzyme treatment (pepsin) or stabilization (beta-propiolactone) is able to influence elimination, fragmentation and organ distribution of intravenously administered gammaglobulins as shown in 36 dogs after i.v. application of allogenic and xenogenic gammaglobulin preparations. Pepsin-gammaglobulin was eliminated and fragmented most rapidly. Gammaglobulin concentrations of all preparations in the skin showed as slower decrease than comparable blood concentrations. The highest skin concentrations 10 days after i.v. application were found for beta-propiolactone gammaglobulin with 6.2 +/- 1.6 microgram/g compared to a blood level of 7.9 +/- 0.9 microgram/ml.

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