Astrocytes synthesize and secrete alpha 2-macroglobulin: differences between the regulation of alpha 2-macroglobulin synthesis in rat liver and brain

Abstract

alpha 2-Macroglobulin (alpha 2M) is an important proteinase inhibitor both in the blood and in the interstitial space of many mammalian species. Recently, occurrence of alpha 2M in human and fetal rat brain has been reported. However, its cellular origin remained obscure. Here it will be shown that astroglial cells cultured from newborn rats synthesize and secrete alpha 2M. In addition to astrocyte primary cultures a rat astrocytoma cell line, C6-cells, also synthesize and secrete alpha 2M. In contrast to hepatocytes of the adult rat, where alpha 2M is expressed as an acute-phase protein and where glucocorticoids and monocyte-derived factors are required for its synthesis, alpha 2M synthesis in astrocytes of newborn rats is independent from both. It is therefore concluded that expression of alpha 2M is differently regulated in the liver of the adult rat and fetal or neonatal brain.