Alpha 2-macroglobulin secretion enhanced in rat hepatocytes by partially characterized factor from Kupffer cells.

Isolated rat Kupffer cells produced a factor which stimulated the synthesis of alpha 2-macroglobulin (alpha 2M) in primary cultured rat hepatocytes. Although Kupffer cells placed in culture produced the factor without stimulation by lipopolysaccharide (LPS), the LPS-stimulated cells produced larger amounts of the factor. On the other hand, the production of the factor was inhibited by addition of actinomycin D. The induction of alpha 2M synthesis by cultured hepatocytes was enhanced in the presence of dexamethasone (Dex), in that hepatic synthesis of alpha 2M increased by addition of the factor alone and with Dex 1.5 and three- to four-fold, respectively. The factor was nondialyzable and stable at 60 degrees C for 30 min. When the factor was fractionated using the molecular sieve method, the activity recovered in the fraction had a molecular weight of over 30,000.