Distribution of ?2-macroglobulin in normal, inflammatory, and tumor tissues in rats

Abstract

Distribution of uptake and catabolism of intravenously administered¹²⁵l-labeled rat α₂-macroglobulin(¹²⁵I-α₂MG) were examined in normal, inflammatory, and tumor tissues of rats. Clearance of intravenously administered [¹²⁵l]α₂MG from the circulation was rapid. Accumulation of this compound into inflammatory tissue was 2–3 times more extensive than in normal tissues. The accumulation into sarcoma tissue was much less. Radioactivity in TCA-PTA precipitates remained fairly constant for the first 12 h in inflammatory tissue and for the first 24 h in sarcoma. These patterns of accumulation were never observed in the normal tissues. As the kidney preferentially accumulated large amounts of [¹²⁵l]α₂MG in the nondegraded form and its degradation products, the tissue may play a special role in the metabolism of α₂MG. Rapid clearance from the circulation and relatively small amounts of accumulation in tissues suggest that α₂MG may function as a protease inhibitor, mainly in the circulation rather than in the tissues.