Kinetics of Selective Deposition of ApoSAA2 During Development of Amyloidosis in Mice
The major murine serum amyloid proteins (apoSAA1, apoSAA2) have been identified, of which only one (apoSAA2) shares amino acid sequence identity with tissue protein AA. To examine the mechanism of this apparent isotype-specific amyloid protein deposition, we have studied apoSAA metabolism at the levels of gene expression and plasma content during amyloidogenesis. In CBA mice, daily intraperitoneal casein administration resulted in a linear increase in splenic amyloid content, beginning within 10 days and reaching approximately 30% of the organ volume at 20 days. Hepatic apoSAA mRNA content, estimated by in vitro translation, was highest at day 1 (3% of total mRNA) and declined thereafter (to 1%, day 20). The relative content of apoSAA2 mRNA compared with that of apoSAA1 was unchanged throughout amyloid induction. Simultaneously, a 2–3 fold drop in total serum apoSAA levels was observed with, by contrast, a 10-fold reduction in the serum ratio of apoSAA2/apoSAA1. These results are consistent with the hypothesis that murine tissue protein AA accumulates by selective deposition of apoSAA2 from the serum.
KeywordsAmyloid Deposition Amyloid Protein Selective Deposition Organ Volume Serum Amyloid Protein
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