SAA is an acute phase reactant and precursor of the major constituent of secondary amyloid fibrils. Studies were done to demonstrate the in vivo synthesis of SAA by hepatocytes. CBA/J mice were injected with 10% casein and serum and hepatic levels measured by radioimmunoassay at 8, 18, 24, and 32 hr. SAA serum levels were elevated by 8 hr (633 ± 49 U/ml, with peak levels at 18 to 24 hr 1933 ± 232 units). Liver tissue levels peaked at 439 ± 37 U/gm at 24 hr and then decreased. In casein-treated animals given colchicine, which inhibits cellular release of protein, there was a blunting of the serum response and a concomitant accumulation of SAA in hepatic tissues (2375 U/gm at 24 hr). Immunohistochemistry with specific antiserum to protein AA showed localization of SAA in hepatocytes starting in periportal areas at 8 hr, and spreading over the entire lobule by 24 hr, when staining was maximal. Colchicine markedly enhanced staining and correlated with hepatic tissue levels of SAA. No localization in spleen sections was found, and minimal levels of SAA were found in spleen tissue by radioimmunoassay. These data are consistent with hepatic synthesis of SAA mediated by a humoral factor that is generated as part of an inflammatory response. Relatively low levels of hepatic SAA are present in casein-treated animals, because SAA exits from the cell very rapidly to give high serum levels within 18 to 24 hr. These kinetics are almost identical to those seen with C-reactive protein in the rabbit, where a humoral factor generated by inflammatory response is also postulated.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Immunology|
|State||Published - Jan 1 1980|
ASJC Scopus subject areas
- Immunology and Allergy